Academic literature on the topic 'Acetic fermentation'

Siwalan (Borassus flabellifer L.) is a palm family that is widely planted in the Tuban area of ​​East Java. Siwalan sap has a relatively high sugar content of about 10-15 g / 100 ml. The sap is obtained by tapping the inflorescences. In general, siwalan sap is used for fresh drinks or alcoholic beverages with maximum storage in 3 days. Based on the sugar content in the sap of siwalan, acetic acid products can be made through fermentation of glucose to ethanol, then the ethanol is fermented into acetic acid. Acetic acid is widely used as a preservative of food and health drinks. The purpose of this research is to study the effect of ethanol fermentation aerobic pH on acetic acid product. Anaerobic fermentation uses saccharomyces cereviceae to produce ethanol, and aerobic fermentation uses acetobacter aceti for acetic acid production. In aerobic ethanol fermentation using pH 3; 3.5; 4 and 5. The concentration of ethanol was analyzed using GC ULTRA Scientific Gas Chromatography, DSQ II detector, and MS 220 column. Acetic acid produced from the aerobic fermentation process was analyzed using an alkalimetric method. Anaerobic fermentation uses Saccharomyces cereviceae with 1-day log phase, while aerobic fermentation uses acetobacter aceti with a 5 day log phase. Aerobic fermentation to produce acetic acid was observed in 5 days to obtained maximum acetic acid concentration, the highest acetic acid concetration is about 2.595 g/l and yield of acetic acid is obtained 0.519% (b/v) at pH 5. Low acetic acid concentration due to low intitial sugar content in siwalan sap.

Background.Not all yeast alcohol dehydrogenase 2 (ADH2) are repressed by glucose, as reported inSaccharomyces cerevisiae.Pichia stipitisADH2 is regulated by oxygen instead of glucose, whereasKluyveromyces marxianusADH2 is regulated by neither glucose nor ethanol. For this reason, ADH2 regulation of yeasts may be species dependent, leading to a different type of expression and fermentation efficiency.Lachancea fermentatiis a highly efficient ethanol producer, fast-growing cells and adapted to fermentation-related stresses such as ethanol and organic acid, but the metabolic information regarding the regulation of glucose and ethanol production is still lacking.Methods.Our investigation started with the stimulation of ADH2 activity fromS. cerevisiaeandL. fermentatiby glucose and ethanol induction in a glucose-repressed medium. The study also embarked on the retrospective analysis of ADH2 genomic and protein level through direct sequencing and sites identification. Based on the sequence generated, we demonstrated ADH2 gene expression highlighting the conserved NAD(P)-binding domain in the context of glucose fermentation and ethanol production.Results.An increase of ADH2 activity was observed in starvedL. fermentati(LfeADH2) andS. cerevisiae(SceADH2) in response to 2% (w/v) glucose induction. These suggest that in the presence of glucose, ADH2 activity was activated instead of being repressed. An induction of 0.5% (v/v) ethanol also increased LfeADH2 activity, promoting ethanol resistance, whereas accumulating acetic acid at a later stage of fermentation stimulated ADH2 activity and enhanced glucose consumption rates. The lack in upper stream activating sequence (UAS) and TATA elements hindered the possibility of Adr1 binding to LfeADH2. Transcription factors such as SP1 and RAP1 observed in LfeADH2 sequence have been implicated in the regulation of many genes including ADH2. In glucose fermentation,L. fermentatiexhibited a bell-shaped ADH2 expression, showing the highest expression when glucose was depleted and ethanol-acetic acid was increased. Meanwhile, S. cerevisiaeshowed a constitutive ADH2 expression throughout the fermentation process.Discussion.ADH2 expression inL. fermentatimay be subjected to changes in the presence of non-fermentative carbon source. The nucleotide sequence showed that ADH2 transcription could be influenced by other transcription genes of glycolysis oriented due to the lack of specific activation sites for Adr1. Our study suggests that if Adr1 is not capable of promoting LfeADH2 activation, the transcription can be controlled by Rap1 and Sp1 due to their inherent roles. Therefore in future, it is interesting to observe ADH2 gene being highly regulated by these potential transcription factors and functioned as a promoter for yeast under high volume of ethanol and organic acids.

Acetic acid fermentation is an essential step in producing high-quality vinegar. In this study, the alcoholic medium was used as a seed broth for acetic fermentation using Acetobacter aceti as the inoculum for approximately 7 days at 32℃ to obtain 45.87g/L acetic acid. During the Acetic acid fermentation stage, the content of the total polyphenols decreased first and then increased. Based on amino acid analyzer analysis, pineapple vinegar contains 18 kinds of free amino acids. And the contents of sweet and umami free amino acids are the main free amino acids, followed by bitter amino acids.

This research is to study the effect of ethanol fermentation aerobic pH on acetic acid product. Anaerobic fermentation uses saccharomyces cerevisiae to produce ethanol, and aerobic fermentation uses acetobacter acetic for acetic acid production. In aerobic ethanol fermentation using pH 3; 3.5; 4 and 5. The ethanol concentration was evaluated using GC ULTRA Scientific Gas Chromatography, DSQ II detector, and MS 220 column. Acetic acid produced was analyzed using an alkalymetric method. Anaerobic fermentation uses Saccharomyces cerevisiae with 1-day log phase, while aerobic fermentation uses acetobacter aceti with a 5-day log phase. Fermentation using saccharomyces cerevisiae within 24 hours so that reduction sugar could stably decrease, optimum ethanol could be got at optimum pH 6 which could decrease 55 % of reducing sugar concentration to produce 8,20583 %v/v ethanol. Fermentation acetate acid content observed in 3 days at pH 6 and 30 ⁰C will produce 6,659 g/l also shows that pH 4-6 at 30 ⁰C will produce 6,605 g/l acetate acid. Aerobic fermentation of acetate acid in 3 days shows that pH 4-6 is highly affected by temperature at 30⁰C. Statistical analysis shows, in ethanol production pH and fermentation time give significant effect, but interaction has no significant effect.

Soybean molasses is a by-product from the production of protein concentrate from soybean meal that predominantly contains sugars, with sucrose as the major component. In Brazil, soybean molasses is used for animal feed or it is discarded, although some industries use it to produce ethanol. This study aims to evaluate the parameters required for the acetic acid fermentation of soybean molasses, and characterise the resultant vinegar. To study the most suitable parameters for the acetic acid fermentation, vinegar was produced from the alcoholic fermentation of soybean molasses through eight fermentation cycles: five for adaptation and three for production. The average acidity of the acetic acid fermentation product was 50.60 g/L, with an acetic acid fermentation yield, total yield of acetic acid in broth and productivity 65.01 %, 92.76 % and 0.033 g/(L·h), respectively. The vinegar produced from soybean molasses had an acidity of 5.07 % (m/V), residual ethanol content 0.17 % (m/V), sugars 7.86 % (m/V), dry extract 14.67 % (m/V), ash 2.27 % (m/V) and a density of 1.023 g/cm3. The contents of total phenolics and isoflavone decreased after the alcohol and acetic acid fermentations. Moreover, the isoflavone profile of the fermented product comprised only three forms: daidzein, glycitin and genistin. According to our results, 3460 L of vinegar can be produced for every tonne of soy molasses, with an acetic acid concentration of 40 g/L, the minimum required by the legislation on vinegar production. Thus, these findings demonstrate that soy molasses represents a useful raw material for the production of vinegar.

ABSTRACT Cocoa fermentations were performed in wooden boxes under the following four experimental regimens: beans naturally fermented with wild microflora; aseptically prepared beans with no inoculum; and beans inoculated with a defined cocktail containing microorganisms at a suitable concentration either at zero time or by using phased additions at appropriate times. The cocktail used consisted of a yeast,Saccharomyces cerevisiae var. chevalieri, two lactic acid bacterial species, Lactobacillus lactis andLactobacillus plantarum, and two acetic acid bacterial species, Acetobacter aceti and Gluconobacter oxydans subsp. suboxydans. The parameters measured were cell counts (for yeasts, filamentous fungi, lactic acid bacteria, acetic acid bacteria, and spore formers, including reisolation and identification of all residual cell types), sugar, ethanol, acetic acid, and lactic acid contents (and contents of other organic acids), pH, and temperature. A cut test for bean quality and a sensorial analysis of chocolate made from the beans were also performed. The natural fermentation mimicked exactly the conditions in 800-kg boxes on farms. The aseptic box remained largely free of microflora throughout the study, and no significant biochemical changes occurred. With the zero-time inoculum the fermentation was almost identical to the natural fermentation. The fermentation with the phased-addition inoculum was similar, but many changes in parameters were slower and less pronounced, which led to a slightly poorer end product. The data show that the nearly 50 common species of microorganisms found in natural fermentations can be replaced by a judicious selection and concentration of members of each physiological group. This is the first report of successful use of a defined, mixed starter culture in such a complex fermentation, and it should lead to chocolate of more reliable and better quality.

ABSTRACTTraditional fermentations of the local Ecuadorian cocoa type Nacional, with its fine flavor, are carried out in boxes and on platforms for a short time. A multiphasic approach, encompassing culture-dependent and -independent microbiological analyses of fermenting cocoa pulp-bean samples, metabolite target analyses of both cocoa pulp and beans, and sensory analysis of chocolates produced from the respective fermented dry beans, was applied for the investigation of the influence of these fermentation practices on the yeast and bacterial species diversity and community dynamics during cocoa bean fermentation. A wide microbial species diversity was found during the first 3 days of all fermentations carried out. The prevailing ethanol-producing yeast species werePichia kudriavzeviiandPichia manshurica, followed bySaccharomyces cerevisiae. Leuconostoc pseudomesenteroides(glucose and fructose fermenting),Fructobacillus tropaeoli-like (fructose fermenting), andLactobacillus fermentum(citrate converting, mannitol producing) represented the main lactic acid bacterial species in the fermentations studied, resulting in intensive heterolactate metabolism of the pulp substrates.Tatumella saanichensisandTatumella punctatawere among the members of the familyEnterobacteriaceaepresent during the initial phase of the cocoa bean fermentations and could be responsible for the production of gluconic acid in some cases. Also, a potential new yeast species was isolated, namely,Candida sorbosivorans-like. Acetic acid bacteria, whose main representative wasAcetobacter pasteurianus, generally appeared later during fermentation and oxidized ethanol to acetic acid. However, acetic acid bacteria were not always present during the main course of the platform fermentations. All of the data taken together indicated that short box and platform fermentation methods caused incomplete fermentation, which had a serious impact on the quality of the fermented dry cocoa beans.

ABSTRACTSecondary fermentations during the bulk storage of fermented cucumbers can result in spoilage that causes a total loss of the fermented product, at an estimated cost of $6,000 to $15,000 per affected tank. Previous research has suggested that such fermentations are the result of microbiological utilization of lactic acid and the formation of acetic, butyric, and propionic acids. The objectives of this study were to characterize the chemical and environmental conditions associated with secondary cucumber fermentations and to isolate and characterize potential causative microorganisms. Both commercial spoilage samples and laboratory-reproduced secondary fermentations were evaluated. Potential causative agents were isolated based on morphological characteristics. Two yeasts,Pichia manshuricaandIssatchenkia occidentalis, were identified and detected most commonly concomitantly with lactic acid utilization. In the presence of oxygen, yeast metabolic activities lead to lactic acid degradation, a small decline in the redox potential (Eh, Ag/AgCl, 3 M KCl) of the fermentation brines, and an increase in pH to levels at which bacteria other than the lactic acid bacteria responsible for the primary fermentation can grow and produce acetic, butyric, and propionic acids. Inhibition of these yeasts by allyl isothiocyanate (AITC) resulted in stabilization of the fermented medium, while the absence of the preservative resulted in the disappearance of lactic and acetic acids in a model system. Additionally, three Gram-positive bacteria,Lactobacillus buchneri, aClostridiumsp., andPediococcus ethanolidurans, were identified as potentially relevant to different stages of the secondary fermentation. The unique opportunity to study commercial spoilage samples generated a better understanding of the microbiota and environmental conditions associated with secondary cucumber fermentations.

Vinegar, composed of various organic acids, amino acids, and volatile compounds, has been newly recognized as a functional food with health benefits. Vinegar is produced through alcoholic fermentation of various raw materials followed by acetic acid fermentation, and detailed processes greatly vary between different vinegar products. This study performed metabolite profiling of various vinegar products using gas chromatography–mass spectrometry to identify metabolites that are specific to vinegar production processes. In particular, seven traditional vinegars that underwent spontaneous and slow alcoholic and acetic acid fermentations were compared to four commercial vinegars that were produced through fast acetic acid fermentation using distilled ethanol. A total of 102 volatile and 78 nonvolatile compounds were detected, and the principal component analysis of metabolites clearly distinguished between the traditional and commercial vinegars. Ten metabolites were identified as specific or significantly different compounds depending on vinegar production processes, most of which had originated from complex microbial metabolism during traditional vinegar fermentation. These process-specific compounds of vinegars may serve as potential biomarkers for fermentation process controls as well as authenticity and quality evaluation.

ABSTRACTFour cocoa-specific acetic acid bacterium (AAB) strains, namely,Acetobacter pasteurianus386B,Acetobacter ghanensisLMG 23848T,Acetobacter fabarumLMG 24244T, andAcetobacter senegalensis108B, were analyzed kinetically and metabolically during monoculture laboratory fermentations. A cocoa pulp simulation medium (CPSM) for AAB, containing ethanol, lactic acid, and mannitol, was used. All AAB strains differed in their ethanol and lactic acid oxidation kinetics, whereby onlyA. pasteurianus386B performed a fast oxidation of ethanol and lactic acid into acetic acid and acetoin, respectively. OnlyA. pasteurianus386B andA. ghanensisLMG 23848Toxidized mannitol into fructose. Coculture fermentations withA. pasteurianus386B orA. ghanensisLMG 23848TandLactobacillus fermentum222 in CPSM for lactic acid bacteria (LAB) containing glucose, fructose, and citric acid revealed oxidation of lactic acid produced by the LAB strain into acetic acid and acetoin that was faster in the case ofA. pasteurianus386B. A triculture fermentation withSaccharomyces cerevisiaeH5S5K23,L. fermentum222, andA. pasteurianus386B, using CPSM for LAB, showed oxidation of ethanol and lactic acid produced by the yeast and LAB strain, respectively, into acetic acid and acetoin. Hence, acetic acid and acetoin are the major end metabolites of cocoa bean fermentation. All data highlight thatA. pasteurianus386B displayed beneficial functional roles to be used as a starter culture, namely, a fast oxidation of ethanol and lactic acid, and that these metabolites play a key role as substrates forA. pasteurianusin its indispensable cross-feeding interactions with yeast and LAB during cocoa bean fermentation.

Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Dr. Rachel Chen; Committee Member: Dr. Athanassios Sambanis; Committee Member: Dr. Sankar Nair. Part of the SMARTech Electronic Thesis and Dissertation Collection.

La fermentation du cacao qui conditionne la qualité aromatique du chocolat, commence par une étape de fermentation alcoolique suivie d’une fermentation acétique, conduites par des souches sauvages de levures et de bactéries acétiques. Réalisée localement à petite échelle, en absence de tout contrôle, elle conduit à des produits finaux de qualité variable, allant du meilleur au pire. Le travail présenté ici fait partie d’un projet qui vise à maitriser la qualité aromatique du chocolat par l’utilisation d’un starter microbien associée à un mode de conduite de la fermentation. Un objectif spécifique est le développement d’un modèle de la fermentation du cacao pour disposer d’un outil permettant le choix d‘un starter et des conditions de sa mise en œuvre. La stratégie de modélisation utilisée est modulaire, pas à pas, avec le souci de construire un modèle simple capable de décrire l’essentiel des processus et des réactions qui occurrent lors de la fermentation. La première étape a été la sélection de deux souches de levures L35 (S. cerevisiae) et L36 (P. kudriavzevii) et d’une souche de bactérie acétique B17 (A. ghanensis) lors de fermentations industrielles ayant conduit à du chocolat de bonne qualité aromatique. Le modèle de la fermentation alcoolique a été développé en utilisant une souche sélectionnée LM (S. cerevisiae) puis a été adapté pour les souches L35 et L36. Le modèle de la fermentation acétique a été développé en utilisant la souche B17. Le modèle global résulte de l’intégration de ces deux sous modèles et d’un modèle permettant de décrire l’élévation de la température des fèves du fait de la production de chaleur lors de la fermentation. Le modèle global permet de décrire assez bien l’ensemble des phénomènes ayant lieu lors de fermentation du cacao : évolution des populations microbiennes, de la consommation/production de glucose, éthanol et acide acétique, et l’évolution de la température, en fonction des conditions initiales (température, concentration en sucres de la pulpe de cacao et niveau d’inoculation du starter). Les résultats de simulations ont permis d’identifier les phénomènes et paramètres clé pour le bon déroulement de la fermentation du cacao. Concernant la fermentation alcoolique, le modèle montre qu’elle est rapide, soit une journée, qu’elle s’achève généralement par l’épuisement des sucres et que la réussite de l’inoculation nécessitera de maitriser la qualité microbiologique de la pulpe de cacao qui dépend du délai entre l’écabossage et l’inoculation. La fermentation acétique avec la souche B17 est conditionnée par la température initiale et l’évolution de la concentration en éthanol qui peut paradoxalement ralentir le démarrage de cette fermentation
The fermentation of cocoa, which drives the aromatic quality of chocolate, begins with an alcoholic fermentation stage followed by an acetic fermentation, conducted by wild strains of yeasts and acetic bacteria. Realized locally on a small scale, in the absence of any control, it leads to products of variable quality, ranging from the best to the worst. The work presented here is part of a project aimed to control the aromatic quality of chocolate using a microbial starter in controlled conditions of fermentation. A specific objective is the development of a model of cocoa fermentation to have a tool allowing the choice of a starter and the conditions of its implementation. The used modeling strategy is modular, step by step, with the aim of building a simple model able of describing the major processes and reactions that occur during fermentation. The first step was the selection of two strains of yeasts, L35 (S. cerevisiae) and L36 (P. kudriavzevii), and a strain of acetic bacteria, B17 (A. ghanensis), during industrial fermentations that led to chocolate of good aromatic quality. The model of alcoholic fermentation was developed using a selected strain LM (S. cerevisiae) and was adapted for strains L35 and L36. The model of acetic fermentation was developed using the B17 strain. The overall model results from the integration of these two sub-models and a model that describes the rise in temperature of the beans due to the production of heat during fermentation. The global model makes it possible to describe quite well all the phenomena that occur during cocoa fermentation: evolution of microbial populations, consumption / production of glucose, ethanol and acetic acid, and the evolution of temperature, depending on initial conditions (temperature, sugar concentration of the cocoa pulp and level of inoculation of the starter). The results of simulations made it possible to identify the key phenomena and parameters for the smooth running of cocoa fermentation. Regarding the yeast fermentation, the model shows that it is fast, one day is sufficient, and usually ends with the exhaustion of sugars and that the success of the inoculation will require control the microbiological quality of cocoa pulp conditioned by the delay between pods opening and the inoculation. The acetic fermentation with B17 strain is conditioned by the initial temperature and the evolution of the ethanol concentration, which can paradoxically slow down the start of this fermentation

Mestrado em Engenharia Alimentat - Processamento de Alimentos - Instituto Superior de Agronomia
It was intended to analyse the entire production process from the arrival of the vinegar factory production, through acetous fermentation, and most actively in the advanced stages to the storage of the finished vinegar. In attempt of the continuous improvement of the vinegars quality, there were investigated the factors that are capable to reduce the quality of this product, ended up in imperfections, like the presence of oxygen and high temperature, in different stages of the global productive process. For this, it was proceeded to a first identification and quantification of defects in stored samples, and further studies which tested the effect of this potential derogatory factors, such as temperature and oxygen, essentially in white wine vinegar, and red wine. The experiments included macroscopic and microscopic observation of bottled vinegars, as well as physico-chemical and microbiological analyses, mostly with regard to the activity of acetic bacteria. The results appearances that this derogatory factors (oxygen and high temperature) are difficult to control. Conclusive results revealed that the vinegar was spoil if exposed to oxygen and high temperatures

Thesis (MScAgric)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: The quality of wine is influenced by numerous factors. These factors include the quality of the grapes, winemaking techniques and quality control throughout the winemaking process. It is thus very important that any process leading to the lowering of the quality of the wine be prevented. Evidence in the wine industry shows that bacterial spoilage is still very much a common problem in many wineries. The spoilage of wine by bacteria can lead to amongst other problems, elevated volatile acidity levels, of which only a certain concentration limit in wine is permitted. Usually more than 90% of the volatile acidity of wine consists of acetic acid. Different yeast strains, heterofermentative lactic acid bacteria and acetic acid bacteria (which can all be spoilage microorganisms) can produce acetic acid in high concentrations. It is thus important to be able to prevent the formation of this acid by controling the unwanted growth of these spoilage microorganisms. Acetic acid and other medium chain fatty acids, octanoic- and decanoic acid, can also lead to stuck or sluggish fermentations. A stuck or sluggish fermentation can also lead to wine spoilage, due to sugar remaining in the fermentation which can be utilized by spoilage microorganisms. Acetic- and other fatty acids enter the yeast cell by passive diffussion and releases its proton in the cytoplasm, thereby acidifying the cytoplasm and inhibiting some enzymes. These acids can also work synergistically with ethanol and its inhibitory effect is also dependent on the temperature. Yeast strains can also differ in their resistance to acetic and other medium chain fatty acids and these acids can also influence the growth of lactic acid bacteria. How acetic acid bacteria influence the winemaking process and the used measures to keep these bacteria from spoiling wine have been the subject of very little attention in the past. This was due to the belief that the anaerobic conditions prevailing in wine and the use of sulfur dioxide are enough to control these bacteria, since acetic acid bacteria were always described as being strictly aerobic microorganisms. Recently, some evidence showed that acetic acid bacteria can survive and even overcome the limits that the winemaking process places on its growth. These bacteria are also known to inhibit the yeasts growth and fermentation ability due to the production of acetic acid and other factors. A research programme on the origin of volatile acidity in South African wines had been initiated at the Department of Viticulture and Enology and at the Institute for Wine Biotechnology at the University of Stellenbosch after increases in volatile acidity in different South African wines had been reported. This spurred us to investigate the occurrence of acetic acid bacteria in South African red wine fermentations, which forms part of this study, and to identify the dominant acetic acid bacterial strains. The sulfur dioxide resistance of five representative strains were also determined, as well as the effect of metabolites which were produced by these bacteria on yeast growth and fermentation ability. Our results indicate that acetic acid bacteria can occur in high concentrations in the fresh must and during alcoholic fermentation. In the 1998 harvesting season acetic acid bacteria occurred at 106-107 cfu per ml in the fresh must. In 1999 these numbers were 104-105 cfu/ml. Acetic acid bacteria numbers decreased in 1998 to 102-103 cfulml during fermentation. The survival of these bacteria in 1999 correlated with the pH of the must, as well as sulfur dioxide dosages in the must. In must with a low pH and higher sulfur dioxide the number of acetic acid bacterial numbers decreased more drastically than in the high pH, low sulfur dioxide musts. This was also true for acetic acid bacterial counts during cold soaking of musts, with the number of acetic acid bacteria increasing during the cold soaking period in musts with a high pH. In musts with a low pH and higher S02 dosages acetic acid bacterial counts did not, however, increase during cold soaking. Gluconobacter oxydans dominated in the fresh must with Acetobacter liquefaciens and especially Acetobacter pasteurianus dominating during the fermentation. Different biochemical and physiological tests revealed that 52% of the 115 isolates tested belong to A. pasteurianus. The high occurrence of A. liquefaciens with A. pasteurianus during fermentation showed that the dominant acetic acid bacterial species in South Africa differed from reports from other wine producing countries. The sulfur dioxide resistance of the acetic acid bacteria tested also differed in white grape juice, with a molecular sulfur dioxide concentration of 0.64 mg/I being necessary to eliminate all the acetic acid bacterial strains tested. The A. hansenii strain was found to be the most resistant to sulfur dioxide and G. oxydans the least resistant. The latter strain was eliminated by only 0.05 mg/I molecular sulfur dioxide, while A. hansenii was only eliminated by 0.64 mg/I molecular sulfur dioxide. The A. pasteurianus, A. liquefaciens and A. aceti strains tested displayed varying degrees of resistance to sulfur dioxide. The volatile acidity produced by these bacteria profoundly influenced the growth and fermentation ability of yeast, which led to slow/stuck fermentation. The A. hansenii and A. pasteurianus strains produced the most volatile acidity in grape juice, with up to 4.02 g/I for A. hansenii within 4 days, which led to a stuck alcoholic fermentation. This was, however, prevented by inhibiting or eliminating the acetic acid bacteria with sufficient sulfur dioxide additions prior to yeast inoculation. Compounds produced by acetic acid bacteria can also influence wine quality. Certain organic acids were produced and metabolized by acetic acid bacteria, as well as acetoin. We could not, however, detect any other fatty acids that are inhibitory to yeast (produced by these bacteria). This study clearly showed that acetic acid bacteria could occur during fermentation and that certain winemaking techniques, like the maintenance of a low pH in the must and sulfur dioxide additions can influence the growth and survival of acetic acid bacteria. Acetic acid bacteria also influence both the winemaking process by inhibiting yeast as well as the quality of the wine by producing acetic acid and/or other compounds. This study also shed some light on the occurrence of acetic acid bacterial species in the South African context and could be important in assisting the winemaker, as well as the scientific reseacher, in finding ways to inhibit acetic acid bacteria in the ongoing battle against these spoilage microorganisms of wine.
AFRIKAANSE OPSOMMING: Wynkwaliteit word deur verskillende faktore beinvloed. Dit sluit die druifkwaliteit, wynmaak tegnieke en kwaliteitsbeheer deur die wynmaakproses in. Enige prosesse en faktore wat tot die verlaging in wynkwaliteit kan lei moet dus ten alle koste voorkom word. Die bederf van wyn deur bakterieë kan en is 'n algemene probleem in enige kelder. Bakteriese bederf kan, onder andere, lei tot verhoogte vlugtige suurheid, waarvan 'n sekere konsentrasie limiet in wyn toegelaat word. Asynsuur maak gewoonlik 90% van die vlugtige suurheid uit. Asynsuur kan deur verskillende gisrasse, heterofermantatiewe melksuurbakterieë en asynsuurbakterieë (wat almal wyn kan bederf) gevorm word. Die vorming van asynsuur in wyn kan dus voorkom word deur die ongewenste groei van dié organismes te voorkom. Asynsuur en ander medium ketting vetsure, soos oktanoë- en dekanoësuur, kan ook tot slepende of gestaakte gistings lei. Suiker wat in die wyn agterbly wat In slepende/gestaakte fermentasie ondergaan kan deur bederf bakterieë gebruik word om die wyn te bederf. Ongedissosieerde asynsuur en ander vetsure dring die gissel binne deur passiewe diffussie en stel 'n proton vry in die sitoplasma wat sitoplasma versuur en sekere ensieme inhibeer. Hierdie sure werk ook sinergisties met etanol en hul inhiberede effek is ook temperatuur afhanklik. Gisrasse verskil in hul weerstandbiedendheid teen asynsuur- en ander mediumketting vetsure en dié vetsure kan ook melksuurbakterieë se groei beïnvloed. Hoe asynsuurbakterieë wyn bederf en die aksies wat geneem kan word om dit te verhoed is in die verlede nie baie ondrsoek nie. Dit is hoofsaaklik daaraan toe te skryf dat geglo is dat die anaerobiese kondisies in wyn en die gebruik van swaweidioksied die groei van asynsuurbakterieë, wat altyd beskryf is as streng aerobe mikroorganismes, kan beheer. Daar is onlangs aangetoon dat asynsuurbakterieë kan oorleef in wyn en selfs die ongunstige kondisies daarin kan oorkom. Hierdie bakterieë is ook in staat om gisgroei en fermentasie vermoë te inhibeer deur die produksie van asynsuur en ander faktore. In Navorsingsprogram om die oorsprong van verhoogde vlugtige suurheid in Suid-Afrikaanse wyne te bepaal is deur die Departement Wingerd- en Wynkunde en die Instituut vir Wynbiotegnologie van die Universiteit van Stellenbosch geinisieer. Dit het ons aangemoedig om die voorkoms van asynsuurbakterieë in Suid-Afrikaanse rooiwyngistings, wat deel vorm van hierdie ondersoek, en ook die dominante asynsuurbakterie rasse te identifiseer. Die swaweidioksied bestandheid van vyf verteenwoordegende rasse en die effek wat metaboliete wat deur dié bakterieë geproduseer is op gisgroei en gisitingsvermoë is bepaal. Ons resultate bewys dat asynsuurbakterieë teen hoë getalle in vars mos en gedurende alkoholiese gisting kan voorkom. Asynsuurbakterieë het gedurende die 1998 seisoen teen 106-107 kve/ml en in 1999 teen 104-105 kve/ml in die vars mos voorgekom. Gedurende fermentasie het hierdie getalle in die 1998 seisoen gedaal na 102-103 kve/ml. Die oorlewing van hierdie bakterieë het gedurende die 1999 seisoen gekorrelleer met die pH en swaweidioksied konsentrasies van die mos. In die lae pH, hoë swaweidioksied moste het asynsuurbakterie getalle vinniger en meer dramaties gedaal as in die hoë pH, lae swaweidioksied moste. Asynsuurbakterie getalle het dieselfde tendens getoon in moste gedurende dopkontak by lae temperature. In moste met 'n hoë pH het asynsuurbakterie getalle toegeneem gedurende koue dopkontak, terwyl dit nie gebeur het nie in moste met 'n lae pH en hoë swaweidioksied konsentrasies. In die vars mos het Gluconobacter oxydans en gedurende die fermentasie Acetobacter liquefaciens en veral Acetobacter pasteurianus oorheers. Verskillende biochemiese en fisiologiese toetse het bepaal dat 52% van die 115 isolate A. pasteurianus is. Die hoë voorkoms van A. liquefaciens saam met A. pasteurianus gedurende gisting bewys dat die voorkoms en dominansie van asynsuurbakterieë in Suid- Afrika verskil van ander wynproduserende lande. Die swaweidioksied weerstandbiedendheid van die asynsuurbakterieë wat getoets het, het ook verskil, met 0.64 mg/I molekulêre swaweIdioksied nodig om hul almal te elimineer in wit druiwesap. Die A. hansenii en G. oxydans rasse was die mees weerstandbiedend en sensitiefste onderskeidelik ten opsigte van swaweidioksied. Slegs 0.05 mg/I molekulêre swaweidioksied was voldoende om G. oxydans te elimineer, terwyl A. hansenii deur 0.64 mg/I molekulêre swaweidioksied geëlimineer is. Die A. pasteurianus, A. liquefaciens en A. aceti rasse het verskillende swaweidioksied weerstandbiedendheid getoon. Die vlugtige suurheid wat deur dié bakterieë geproduseer is het die groei en gistingvermoë van gis drasties beinvloed, wat tot slepende/gestaakte fermentasies gelei het. Die A. hansenii en A. pasteurianus rasse het die meeste vlugtige suurheid geproduseer, met tot 4.02 g/I geproduseer deur A. hansenii na vier dae se groei, wat tot 'n gestaakte fermentasie gelei het. Dit is egter voorkom deur die asynsuurbakterieë te elimineer deur genoegsame swaweidioksied toevoegings tot die mos voor gisinokulasie te doen. Verbindings wat deur asynsuurbakterieë geproduseer word kan ook wynkwaliteit beinvloed. Sekere anorganiese sure is deur hierdie bakterieë geproduseer, terwyl ander gemetaboliseer is. Asetoïen is geproduseer deur die getoetse asynsuurbakterieë. Ons kon egter nie ander vetsure wat gis inhibeer opspoor nie. (Geproduseer deur die bakterieë). Hierdie studie bewys dat asynsuurbakterieë gedurende alkoholiese fermentasie kan voorkom en dat sekere wynmaaktegnieke, soos die verkryging van moste met 'n lae pH en genoegsame swaweidioksied toevoegings die groei en oorlewing van asynsuurbakterieë kan beivloed. Asynsuurbakterieë kan ook beide die wynmaakproses, deur giste te inhibeer, en die wynkwaliteit beivloed deur die produksie van asynsuur en/of ander verbindings. Hierdie studie het ook kennis oor die voorkoms van asynsuurbakterieë in Suid-Afrikaanse moste verbeter en kan ook as 'n nuttige hulpmiddel dien vir die wynmaker en navorser in die stryd om hierdie bederf organismes van wyn te elimineer.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.
Grape producers and wine makers in South Africa are currently affected by various challenges, which include anti-alcohol lobbies, climate change, over-production in some vintages and the lack of transformation including empowerment in certain sectors of the industry. Climate change and global warming lead to poor quality wine grapes and as a result, poor quality wine. Therefore, there is a need to channel grapes away from normal wine production and provide an alternative source of income for the industry. The overall aim of this study was therefore to provide an alternative outlet for overproduced wine grapes by producing balsamic-styled vinegar (BSV) in South Africa. Balsamic vinegar is different from other vinegars because it is a direct product of grape must and not a downstream or by-product of wine production. Balsamic vinegar entails lower production costs when compared to the production of wine due to the low technological process requirements during production; therefore, this could be an opportunity for small business entrepreneurs with low capital start-up. In addition, balsamic vinegar can command a high price, which is a benefit for grape producers. The primary aim of this investigation was to biochemically analyse a BSV production process in which 5 non-Saccharomyces yeast and 15 acetic acid bacteria (AAB) were used for a multicultural alcoholic-acetous (EtOH-AcOH) fermentation process. To achieve this aim, a fermentation process was designed where the data generated was fitted into kinetic models and the proliferation including the population dynamics of the microbial consortia were studied.

Les énergies non-renouvelables ont été d’un apport capital dans l’industrialisation et l’urbanisation dans les derniers centenaires. L’exploitation excessive des réserves d’hydrocarbures et son impact environnemental ont contribué au developpement de plusieurs technologies durables à caractère néo-carbone neutre. A cet effet, les processus biologiques comme la fermentation pourraient être exploités pour convertir biologiquement le hydrates de carbone en énergies comme l’hydrogène (H2) ou des acides organiques commercialement rentables. Ce travail a étudié les techniques d’ingénierie pour améliorer la synthèse simultanée d’H2 et d’acide lactique à travers des conditions de fermentation capnophile lactique (CLF) par une souche de labo de Thermotoga neapolitana.En un premier temps, une comparaison génotypique entre la souche de labo et celle sauvage a révélé une ressemblance de 88,1 (±2,4) %. En plus, les analyses du génotypage par RiboPrint® et par spectroscopie de masse matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF MS) ont montré une différentiation génétique au-delà du niveau sous-espèce ; et par conséquent la souche de labo a été proposée comme sous-espèce, T. neapolitana subsp. lactica. Basé sur la caractérisation phénotypique, la souche de labo produisait 10-90% plus d’acide lactique que celle sauvage sous les mêmes conditions sans pour autant affecté le taux de production d’H2.La souche de labo a donc été étudiée pour aussi bien optimiser les conditions de croissance que pour estimer les paramètres cinétiques de croissance. Un nouveau modèle cinétique basé sur les principes de fermentation à l’obscurité (DF) et les expressions mathématiques Monod ont été développés pour permettre la simulation de la croissance en biomasse, la consommation de substrat, et la formation de produit. Le modèle n’a cependant pas pu faire une estimation des acides acétique et lactique avec précision du fait que le modèle DF n’a pas considéré la carboxylation de l’acide acétique en acide lactique par l’enzyme pyruvate ferrédoxine oxydoréductase (PFOR) sous les conditions CLF.Le model a été associé avec le mécanisme CLF et les paramètres cinétiques ont été recalibrés. Les paramètres cinétiques que sont le taux d’absorption spécifique maximum (k), la constante semi-saturation (ks), le coefficient en rendement biomasse (Y), et le taux de décomposition interne (kd) étaient de 1,30 l/h, 1,42 g/L, 0,12 et 0,02 l/h. Fait intéressant, le nouveau modèle CLF s’est parfaitement adapté avec les résultats expérimentaux et a estimé que près de 40-80% de la production d’acide lactique est attribué au recyclage de l’acide acétique et le CO2.En plus, l’adsorption de l’acide lactique par le carbone actif et les résines polymères anioniques a été appliquée avec succès comme technique de transformation en aval dans la récupération et la purification de l’acide lactique à partir du modèle de fermentation type T. neapolitana. Pour ce faire, ce travail de recherche constitue une étape majeure dans le domaine de la fermentation bactérienne utilisable pour de vastes applications scientifiques prenant en compte le développement d’énergies renouvelables et la production industrielle d’acide lactique
The environmental impact of excessive exploitation of fossil fuel reserves has inspired the innovation of several sustainable neo-carbon-neutral technologies. To that end, the biological processes like fermentation may be leveraged to bioconvert carbohydrate-rich feedstocks to fuels like hydrogen (H2) or commercially valuable organic acids like lactic acid. This research work investigated the engineering techniques for improving simultaneous synthesis of H2 and lactic acid under capnophilic (CO2-dependent) lactic fermentation (CLF) conditions by a lab strain of Thermotoga neapolitana.Primarily, the genotypic comparison between the lab strain and the wild-type revealed DNA homology of 88.1 (± 2.4)%. Genotyping by RiboPrint® and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses showed a genetic differentiation beyond subspecies level, hence the lab strain was proposed as a new subspecies, T. neapolitana subsp. lactica. The lab strain produced 10-90% more lactic acid, based on the phenotypic characterization, than the wild-type strain under similar operating conditions without impairing the H2 yield.The lab strain was then studied to optimize the growth conditions as well as to estimate the growth kinetic parameters. A new mathematical model based on the dark fermentation (DF) principles and Monod-like kinetic expressions was developed to enable the simulation of biomass growth, substrate consumption and product formation. The model failed to estimate acetic and lactic acid accurately, as the DF model did not consider the carboxylation of acetic acid to lactic acid by the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme under CLF conditions. The model was then incorporated with the CLF mechanism and the kinetic parameters were recalibrated.The calibrated kinetic parameters, i.e. maximum specific uptake rate (k), semi-saturation constant (kS), biomass yield coefficient (Y) and endogenous decay rate (kd) were 1.30 1/h, 1.42 g/L, 0.12 and 0.02 1/h, respectively, under CLF conditions. The new CLF-based model fitted very well with the experimental results and estimated that about 40-80% of the lactic acid production is attributed to the recycling of acetic acid and CO2.In addition, the adsorption of lactic acid by activated carbon and anionic polymeric resins was successfully applied as a downstream processing technique for the recovery of lactic acid from a model T. neapolitana fermentation broth. This research work serves as a practical milestone in the field of microbial fermentation with a scope for wider scientific applications, including the development of bio-based renewable energy and industrial lactic acid production

A amora-preta (Rubus sp.) faz parte do grupo das chamadas “pequenas frutas” e apresenta propriedades nutricionais relevantes, como elevados conteúdos de sais minerais, vitaminas e compostos bioativos com atividades biológicas. Tais compostos podem auxiliar na prevenção de doenças cardiovasculares, câncer, retinopatia diabética, doença fibrocística e desordens da visão entre outros males. No entanto, a fruta apresenta estrutura frágil e elevada atividade respiratória o que resulta em vida de prateleira reduzida. Desta forma, é tecnicamente importante o desenvolvimento de produtos derivados que mantenham as propriedades nutricionais e compostos bioativos da fruta. Nesse sentido, o presente trabalho teve como objetivo o aproveitamento tecnológico da amora-preta no desenvolvimento de vinagres através dos processos submerso e lento com ciclos sucessivos de acetificação. Inicialmente foi produzido fermentado alcoólico em biorreator de bancada e na sequência foram produzidos fermentados acéticos em vinagreira de grápia e biorreator de bancada. Na fermentação alcoólica foi empregada cepa industrial de Saccharomyces cerevisae r.f. bayanus e na fermentação acética, cepas selvagens de bactérias ácido-acéticas isoladas de vinagre colonial no município de Pato Branco. No processo de fermentação alcoólica foram observados rendimento de 0,39 g/g, produtividade volumétrica em etanol de 1,77g/Lh e eficiência de 75,5%, bem como elevados conteúdos de polifenóis (983,35 mg GAE/100g e 1.702,52 mg GAE/100g). Nos ciclos sucessivos de acetificação conduzida em vinagreira foi obtida produção média de 51,6 g/L de ácido acético, rendimento em ácido acético de 72,2% e produtividade volumétrica de 0,4 g/Lh. Por outro lado, menores valores de produção média de ácido acético (42,26 g/L) e rendimento (70,2%) foram observados no processo de acetificação conduzido em biorreator de bancada. Elevados conteúdos de polifenólicos, antocianinas e elevada atividade antioxidante foram obervados nos vinagres obtidos em ambos os processos de produção. Os vinagres produzidos a partir de amora-preta podem ser considerados vinagres do tipo gourmet que apresentam potencial funcional e a transformação da fruta em vinagre pode ser uma estratégia de agregação de valor a cadeia produtiva colaborando para disseminação da cultura no Brasil.
Blackberry (Rubus sp) is part of the so-called berries, presenting remarkable nutritional features, such as high content of mineral salts, vitamins and bioactive compounds with biological activity. Such compounds may aid in the prevention of cardiovascular diseases, cancer, diabetic retinopathy, fibrocystic and eye diseases, among others. Nevertheless, blackberry presents a fragile structure and a high respiratory activity, resulting in reduced shelf-life. In this way, it is important, from a technological viewpoint, to develop new products derived from blackberry which preserve the fruit original nutritional quality and bioactive compounds. Thus, the present work aimed at the technological utilization of blackberry for developing vinegar by means of the submerged and the slow processes with successive cycles of acetification. Initially, an alcoholic fermented product was obtained in stirred tank bioreactor. Subsequently, acetic fermented products were obtained either in a grapia (Brazilian ash) vinegar barrel or in a bench bioreactor. In the alcoholic fermentation, an industrial strain of Saccharomyces cerevisiae r.f. bayanus was used. In the acetic fermentation, wild strain of acetic acid bacteria isolated from colonial vinegar from Pato Branco city was used. The alcoholic fermentation presented yield of 0.39 g/g, volumetric productivity of 1.77 g/Lh and efficiency of 75.5%, besides high polyphenol contents (983.35 mg GAE/100g and 1702.52 mg GAE/100g). In the successive acetification cycles performed in grapia barrel, average production of 51.6 g acetic acid/L, yield of 72.2% (as acetic acid) and volumetric productivity of 0.4 g/Lh were observed. On the other hand, the acidification performed in bench bioreactor presented lower values of average production (42.26 g acetic acid/L) and yield (70.2%). High polyphenols and anthocyanins content along with high antioxidant activity were observed in the vinegars obtained by both production processes. Vinegars produced from blackberry can be considered gourmet vinegars with high functional potential. The transformation of blackberry into vinegar might be a strategy of value addition to the production chain, contributing for spreading this culture in Brazil.

L’utilizzo degli scarti da parte dell’industria alimentare costituisce una sfida importante per ridurre le perdite di cibo, aumentare la sostenibilità della produzione alimentare e, pertanto, incrementare la sicurezza alimentare specialmente nei paesi in via di sviluppo. Obiettivo della presente tesi è ottenere aceto dagli scarti dell’ananas tramite idrolisi enzimatica preceduta da pre-trattamento fisico, fermentazione alcolica con differenti ceppi di Saccharomyces cerevisiae, addizionati di Lactobacillus delbruekii o Lactobacillus plantarum del liquido saccarificato, e fermentazione acetica con Acetobacter aceti in un impianto pilota. I campioni ottenuti dalle prove di saccarificazione, fermentazione alcolica e acetica sono stati analizzati per pH, acidità totale, grado Brix, zuccheri, acidi organici, etanolo e per i composti volatili. Una caratterizzazione dettagliata dell’aceto è stata eseguita tramite UPLC/Q-TOF e GC-MS.
Using waste from the food industry is a major challenge to reduce food losses, to increase the sustainability of food production and, therefore, increase food security, especially in developing countries. The objective of this thesis is to get vinegar from pineapple waste by means of: enzymatic hydrolysis proceeded by physical pre-treatment; alcoholic fermentation of the saccharified juice with different strains of Saccharomyces cerevisiae and Lactobacillus delbruekii or Lactobacillus plantarum; acetic fermentation with Acetobacter aceti in a pilot plant. Samples obtained from saccharification, alcoholic and acetic fermentation were analyzed for pH, total acidity, total soluble solid (TSS), sugars, acids, ethanol, and volatile compounds. A detailed characterization of vinegar was carried out through UPLC/Q-TOF and GC-MS.

The purpose of this study was to determine the effect of homo- and hetero-fermentative lactic acid bacteria mix on the ensiled lucerne fermentation characteristics and aerobic stability in big bales. The lucerne was ensiled without additives (C) and treated with a mix of bacterial inoculant that contains Lactococcus lactis and Lactobacillus buchneri (50:50) (I). Silage was treated with bacterial inoculant, which significantly increased the total organic acids concentration by 69 %, lactic acid by 92% and acetic acid by 76 %. If the results were compared with the C silage, the inoculation significantly decreased the concentrations of butyric acid by 73 %, ethanol by 53 % and ammonia - N concentration by 33%. Inoculated silage had significantly lowered the yeast count by 59 % and moulds count by 34 %. Compared to the inoculated silage and during the aerobic exposure, the untreated silage maximum temperature was significantly higher (13.9 0C vs 4.6 0C) (P < 0.05). Therefore, the bacterial inoculant improved the quality of fermentation and aerobic stability in lucerne silages.

The article describes the technology of making apple and apple-pear vinegars from natural raw materials. Described is the process of aerobic oxidation occurring in alcoholic fermentation of raw materials in the presence of acetic acid bacteria. The work carried out an organoleptic assessment and comparative analysis of samples of the finished product. Based on this, a conclusion was made about the compliance