Dissertations / Theses on the topic 'Sweet sorghum ethanol: Sweet sorghum silage'

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The sorghum was investigated as a food source to replace corn and alternative to sugar cane for ethanol production. Experimental in the State University of Paraná- UNIOESTE West station in Rondon-PR, with the hybrid ADV 2010, which was ensiled and processed with the same equipment already used in the processing of corn and sugarcane, produced a quantity of biomass that exceeded the volume of 165,000 kg of fresh weight per hectare in two sections with an ethanol production of 1,035 liters per hectare in the 1st section and 695 liters per hectare in regrowth, resulting in a cost of R$ 1.26 per liter produced in a rural property. The chemical composition of silage dry matter, acid detergent fiber, neutral detergent fiber, ash and crude protein were relevant in the silage. The results showed that there is viability in producing ethanol from sweet sorghum in rural properties, an additional investment. The economic potential of the material, addition of ethanol and silage extends to the biomass, which can be used for other purposes, and food, can be dried and incorporated into animal feed (fiber) in digesters supply or production steam boilers.
O sorgo sacarino foi investigado como fonte de alimento em substituição ao milho e alternativa à cana de açúcar para a produção de etanol. Na Estação Experimental da Universidade Estadual do Oeste do Paraná-UNIOESTE em Marechal Cândido Rondon-PR, com o híbrido ADV 2010, que foi ensilado e processado com os mesmos equipamentos já usados no processamento de milho e cana, produziu uma quantidade de biomassa que superou o volume de 165.000 kg de massa fresca por hectare em dois cortes, com uma produção de etanol de 1.035 litros por hectare no 1º corte e de 695 litros por hectare no rebrote, resultando num custo de R$ 1,26 por litro produzido em uma propriedade rural. A composição bromatológica da silagem em matéria seca, fibra em detergente ácido, fibra em detergente neutro, matéria mineral e proteína bruta mostraram-se relevantes nas silagens. Os resultados mostraram que há viabilidade em produzir etanol a partir do sorgo sacarino em propriedades rurais, mediante um investimento adicional. O potencial econômico do material, além da produção de etanol e silagem, se estende à biomassa, que pode ser usada para outros fins, além de alimentação, também pode ser secado e incorporado à rações (fibras), em alimentação de biodigestores ou produção de vapor em caldeiras.

The use of fossil fuels contributes to global warming and there is a consequent need to resort to clean and renewable fuels. The major concerns with using agricultural crops for the production of energy are food and water security. Crops that do not threaten food security and that can be cultivated with a relatively low amount of water and produce high yields of fermentable sugars are therefore needed. Sweet sorghum is a fastgrowing crop that can be harvested twice a year and that can produce both food (grain) and energy (sugar juice from stems). Sweet sorghum bagasse can also be utilised for ethanol production. The aim of this study was to determine the sugar content of different sweet sorghum cultivars at different harvest times, and determine the cultivar that will produce the highest ethanol yield at optimized fermentation conditions. Sweet sorghum bagasse was also pretretated, enzymatic hydrolysed and fermented and the best pretreatment method and ethanol yield was determined. In this study, sweet sorghum juice, which mostly consists of readily fermentable sugars (glucose, sucrose and fructose), as well as the bagasse obtained after juice extraction, were converted to bio–ethanol. Sweet sorghum juice was fermented to ethanol using Saccharomyces cereviciae without any prior pretreatment. The effect of pH (4–6), yeast concentration (1–5g.L–1), initial sugar concentration (110–440g.L–1) and the addition of a nitrogen source (urea, ammonium sulphate, yeast extract and peptone) on the ethanol yield was investigated. The pretreatment of bagasse using sulphuric acid (3wt %), and calcium hydroxide (0.2g/g bagasse), followed by enzymatic hydrolysis using Celluclast 1.5L (0.25g/g bagasse), Novozyme 188 (0.24g/g bagasse) and Tween 80(1.25g.L–1) were adapted from Mabentsela (2010). Fermentation was done using Saccharomyces cerevisiae, but it was unable to ferment the xylose sugar. The results show that the USA 1 cultivar contains the highest sugar content at 3 months. An ethanol and glycerol yield of 0.48g.g–1 and 0.05g.g–1 was observed respectively at a pH of 4.5, a yeast concentration of 3wt%, initial sugar concentration of 440g.L–1 and when ammonium sulphate was added to the fermentation broth as nitrogen source. The glycerol yield formed as a by–product during fermentation and at a maximum ethanol yield was 0.05g.g–1. The glucose yield obtained from sulphuric acid, base and ultrasonic wave pretreatment was 0.79g.g–1, 0.62g.g–1 and 0.62g.g–1 respectively. The glucose yield obtained after each type of pretreatment was higher than that obtained for unpretreated bagasse, which was 0.55g.g–1. Base pretreatment, ultrasonic wave pretreatment and unpretreated bagasse also contained fructose at the end of enzymatic hydrolysis. Base, sulphuric acid pretreatment disrupted the crystal structure of cellulose and increased the available surface, and therefore cellulose was easily accessible for enzymatic hydrolysis. Ultrasonic wave pretreatment showed potential in increasing the surface area for enzymatic hydrolysis but further investigations need to be done. From bagasse fermentation, 0.45g.g–1 – 0.39g.g–1 of ethanol per g of available fermentable sugar was obtained.
Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Doctor of Philosophy
Department of Biological & Agricultural Engineering
Donghai Wang
Sweet sorghum accumulates high concentrations of fermentable sugars in the stem, produces significant amount of starch in the grain (panicle) and has shown to be a promising energy feedstock. Sweet sorghum has a short growing season so adding it to the sugar cane system would be good. The overall goal of this dissertation is to enhance the attractiveness of biofuel production from sweet sorghum to fully utilize fermentable sugars in the juice, starch in the panicle and structural carbohydrates in the stalk for high efficiency and low-cost ethanol production. Sweet sorghum juice was incorporated into the dry-grind process which increased ethanol yield by 28% increase of ethanol yield compared to the conventional ethanol method and decreased enzymatic hydrolysis time by 30 minutes. A very high gravity fermentation technique was applied using sweet sorghum juice and sorghum grain yielded 20.25% (v/v) of ethanol and 96% fermentation efficiency. Response surface methodology was applied in order to optimize diffusion conditions and to explore effects of diffusion time, diffusion temperature, and ratio of sweet sorghum biomass to grain on starch-to-sugar efficiency and total sugar recovery from sweet sorghum. Starch hydrolysis efficiency and sugar recovery efficiency of 96 and 98.5% were achieved, respectively, at an optimized diffusion condition of 115 minutes, 95 °C, and 22% grain loading. Extraction kinetics based on the optimized diffusion parameters were developed to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Ethanol obtained from fermented extracted sugars treated with granular starch hydrolyzing enzyme and those with traditional enzymes were comparable (14.5 – 14.6% v/v). Ethanol efficiencies also ranged from 88.92 –92.02%.

BACKGROUND:Sweet sorghum is a domesticated grass containing a sugar-rich juice that can be readily utilized for ethanol production. Most of the sugar is stored inside the cells of the stalk tissue and can be difficult to release, a necessary step before conventional fermentation. While this crop holds much promise as an arid land sugar source for biofuel production, a number of challenges must be overcome. One lies in the inherent labile nature of the sugars in the stalks leading to a short usable storage time. Also, collection of sugars from the sweet sorghum stalks is usually accomplished by mechanical squeezing, but generally does not collect all of the available sugars.RESULTS:In this paper, we present two methods that address these challenges for utilization of sweet sorghum for biofuel production. The first method demonstrates a means to store sweet sorghum stalks in the field under semi-arid conditions. The second provides an efficient water extraction method that can collect as much of the available sugar as feasible. Operating parameters investigated include temperature, stalk size, and solid-liquid ratio that impact both the rate of sugar release and the maximal amount recovered with a goal of low water use. The most desirable conditions include 30degreesC, 0.6 ratio of solid to liquid (w/w), which collects 90 % of the available sugar. Variations in extraction methods did not alter the efficiency of the eventual ethanol fermentation.CONCLUSIONS:The water extraction method has the potential to be used for sugar extraction from both fresh sweet sorghum stalks and dried ones. When combined with current sugar extraction methods, the overall ethanol production efficiency would increase compared to current field practices.

Sweet sorghum has potential as an energy crop in the Southwest since, compared to corn, it requires less fertilizer and water, is cheaper to grow, and requires less energy to process into ethanol. The purpose of this study is to determine the feasibility of obtaining two crops of sweet sorghum from a single seeding. Two cultivars of sweet sorghum were seeded at early and late dates at the Maricopa Agricultural Center in 2006. Two crops of sweet sorghum were obtained in our study with a short season cultivar Bundle King, but not with the longer season cultivar MMR 327/36. The ethanol yield of Bundle King of 213 gal/acre from two crops planted on April 7 was not significantly greater statistically than the ethanol yield of 162 gal/acre from a single crop planted on June 1. Bundle King is an inherently low yielding variety, as are most short season sweet sorghum cultivars that may be used for double cropping. Thus, the problem with double cropping is identifying a suitable cultivar along with increased harvest costs, despite the advantage of providing a more even supply of feedstock to an ethanol plant.

The goal of this project was to design an ethanol production process from sweet sorghum for use as a renewable fuel. Sorghum stalks are first harvested and sent through a series of 2 three-roller extractors (70% total efficiency). Extracted juice is pumped to the reactor for preservation and fermentation. Sodium metabisulfite preserves the juice. Ethanol Red (Saccharomyces cerevisiae) is the fermentation yeast. Following fermentation, the juice (8% ethanol by mass) is distilled to achieve 90% ethanol. A molecular sieve extracts excess water, resulting in 100% ethanol. Plant wastes accumulate during the process. These wastes are collected, dried, and sold as animal feed for profit. The project economics indicate that the overall process is not currently economically feasible. The net present value (NPV) for the optimum economic situation, assuming a 15 year plant lifetime and 15% interest rate, is -$125 M. Under these circumstances, the ethanol would need to be sold at $44.37 per gallon to break even. To improve this process, further development of methods for increasing juice extraction efficiency should be explored. Additionally, the distillation process could be enhanced with a second distillation column to achieve 95% ethanol prior to using the molecular sieve.

The utilization of lignocellulosic residues to produce renewable energy is an interesting alternative to meet the increasing demand of fuels while at the same time reducing greenhouse gas emissions and climate change. Sweet sorghum bagasse is a lignocellulosic residue composed mainly of cellulose, hemicellulose, and lignin; and it is a promising substrate for ethanol production because its complex carbohydrates may be hydrolyzed and converted into simple sugars, and then fermented into ethanol. However, the utilization of lignocellulosic residues is difficult and inefficient. Lignocellulose is a very stable and compact complex structure, which is linked by β-1,4 and β-1,3 glycosidic bonds. Furthermore, the crystalline and amorphous features of cellulose fibers and the presence of hemicellulose and lignin make the conversion of lignocellulose into fermentable sugars currently impractical at commercial scale. The bioconversion of lignocellulose in nature is performed by microorganisms such as fungi and bacteria, which produce enzymes that are able to degrade lignocellulose. The present study evaluated the bioconversion of lignocellulosic residues of sweet sorghum into simple sugars using filamentous fungi directly in the hydrolysis of the substrate, without prior isolation of the enzymes. The fungus Neurospora crassa and some wild fungi (that grew naturally on sweet sorghum bagasse) were used in this investigation. The effect of the fungi on substrate degradation and the sugars released after hydrolysis were evaluated, and then compared with standard hydrolysis performed by commercial enzymes (isolated cellulases). In addition, different combinations of fungi and enzymes were used to determine the best approach. The main goal was to verify if the fungi were able to attack and break down the lignocellulose structure directly and at a reasonable rate, rather than by the current method utilizing isolated enzymes. The main finding of this study was that the fungi (N. crassa and wild fungi) were able to degrade sweet sorghum bagasse directly; however, in all of the cases, the hydrolysis process was not efficient because the hydrolysis rate was much lower than the enzymatic hydrolysis rate. Hydrolysis using a combination of fungus and commercial enzymes was a good approach, but still not efficient enough for practical use. The best results of combined hydrolysis were obtained when the substrate was under the fungus attack for three days and then, commercial enzymes with low enzymatic activity (7 FPU/g and 25 CBU/g) were added to the solution. These enzymes represent 10% of the current enzymatic activity recommended per gram of substrate. This process reached reasonable levels of sugars (close to 85% of sugars yield obtained by enzymatic hydrolysis); however, the conversion rate was still slower, making the process impractical and more expensive since it took twice the amount of time as commercial enzymes. Furthermore, the wild fungi able to degrade cellulose were isolated, screened, and identified. Two of them belong to the genus Aspergillus, one to the genus Acremonium, and one to the genus Rhizopus. Small concentration of spores-0.5mL- (see Table 4, CHAPTER III- for specific number of spores per mL) did not show any sugar released during hydrolysis of sweet sorghum bagasse. However, when the concentration of spores was increased (to 5mL and 10mL of solution), citric acid production was detected. This finding indicates that those wild fungi were able to degrade lignocellulose, even though no simple sugars were measured, citric acid production is an indicator of fungi growing and utilization of lignocellulose as nutrient. It is assumed that the fungi consume the sugars at the same time they are released, thus they are not detected. The maximum concentration of citric acid (~14.50 mg/mL) was achieved between days 8-11 of hydrolysis. On the other hand, before using lignocellulose, the substrate needed to be pretreated in order to facilitate its decomposition and subsequent hydrolysis. Sweet sorghum bagasse was washed three times to remove any soluble sugars remaining after the juice was extracted from the stalks. Then, another finding of this study was that the first wash solution could be used for ethanol production since the amount of sugars present in it was close to 13°Brix. The ethanol yield after 48 hours of fermentation was in average 6.82mg/mL, which is close to the theoretical ethanol yield. The other two washes were too dilute for commercial ethanol production. In terms of pretreatments, the best one to break down sweet sorghum bagasse was 2% (w/v) NaOH. This pretreatment shows the highest amounts of glucose and xylose released after hydrolysis. Unwashed and untreated bagasse (raw bagasse) did not show any sugar released. In terms of ethanol, 74.50% of the theoretical yield was reached by enzymatic hydrolysis, while 1.10% was reached by hydrolysis using the fungus N. crassa. Finally, it is important to remark that further investigation is needed to improve the direct conversion of lignocellulose into fermentable sugars by fungal enzymes. This approach is a promising technology that needs to be developed and improved to make it efficient and feasible at commercial scale.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Currently sweet sorghum (Sorghum bicolor (L.) Moench) has become very important for the energy sector and sugarcane in Brazil, which is constantly seeking alternatives to increase agricultural and industrial yields, especially in the off season of cane sugar, decreasing the idle time and production costs. It is a rustic agricultural species, with good adaptation to environmental stresses, such as those found in the Northeast, with features similar to stalks of sugarcane juice rich in fermentable sugars, and can be used to produce ethanol in the same facility used by the cane sugar. The culture is totally mechanized (by planting seeds, and harvesting), high productivity of green biomass (60-80 t ha-1), with high yields of ethanol (3000-6000 l.ha-1), bagasse usable as a source of energy (steam and electricity cogeneration industrialization). The present study was designed to indicate the most suitable for a probable launch as a variety to be grown in the Zona da Mata, Region of the State of Pernambuco, Northeast, Brazil genotypes. For this purpose, an experiment was carried out from February to June 2014 in the experimental field at the Pernambuco Agricultural Institute Enterprise - IPA, in Vitória de Santo Antão, Pernambuco. The study consisted of 65 progenies that are the result of segregation F6 a cross between two varieties (IPA467-4-2 X IPA 2502), where the first strain was used as male parent and the second as the female parent, were obtained in Vitória Santo Antão - PE in 2010, tested in Caruaru - PE in 2011 and retested in Vitória de Santo Antão - PE in 2013, more than 15 witnesses were commercial varieties in the region, including these two parental strains. The experiment was designed in randomized blocks, consisting of 80 plots and 3 replications, where each portion had dimensions of 6.0 x 0.8 m, with a total area of 4.80 m2 and is considered an area of 3.20 m² (0 , 8 x 4m), eliminating the first meter of each boundary. Variables according to the production characteristics presented in the field were analyzed: average height of plant (AMP); Days to flowering (FL); Total production of green matter (PMV); Production Shed (PCL) and Percentage of thatch to produce total green matter (% CL). Besides the agroindustrial features: Production of total dry matter (PMS); Percentage of total dry matter (% MST); Production Shed (PCL); Harvesting Brix (Brix); Extraction efficiency of broth (EEC) and theoretical Ethanol (ET). Means were compared by Scott - Knott test at 5% level of probability, genetic correlations being conducted to complement the study of these variables.
Atualmente o sorgo sacarino (Sorghum bicolor (L.) Moench) apresenta-se muito importante para o setor sucroalcooleiro e energético do Brasil, que vem buscando constantemente alternativas para aumentar rendimentos agrícolas e industriais, principalmente na entressafra da cana-de-açúcar, diminuindo o tempo ocioso e os custos de produção. É uma espécie agrícola rústica, com boa adaptação a estresses ambientais, tais como os encontrados na Região Nordeste, apresenta colmos com caldo semelhante ao da cana, rico em açúcares fermentescíveis, e pode servir para a produção de etanol na mesma instalação utilizada pela cana-de-açúcar. A cultura é totalmente mecanizável (plantio por sementes, tratos culturais e colheita), alta produtividade de biomassa verde (60 a 80 t.ha-1), com altos rendimentos de etanol (3.000 a 6.000 l.ha-1), com bagaço utilizável como fonte de energia (vapor para industrialização e cogeração de eletricidade). O presente trabalho teve como objetivo avaliar o potencial de novas progênies F6 de sorgo de duplo propósito (grão e forragem, incluindo colmo seco e sacarino), visando definição de aptidão e uso. Para tanto, foi conduzido um experimento nos meses de fevereiro a junho de 2014, no campo experimental no Instituto Agronômico de Pernambuco – IPA, no município de Vitória de Santo Antão-PE. O estudo foi composto por 65 progênies que são resultado da segregação F6 do cruzamento entre duas variedades (IPA 467-4-2 X IPA 2502), onde a primeira variedade foi utilizada como parental masculino e a segunda como parental feminino, sendo obtidas em Vitória de Santo Antão – PE em 2010, testadas em Caruaru – PE em 2011 e novamente testadas em Vitória de Santo Antão – PE em 2013, mais 15 testemunhas que foram variedades comerciais na região, incluindo nestas as duas variedades parentais. O experimento foi delineado em blocos casualizados, composto por 80 parcelas e 3 repetições, onde cada parcela teve dimensões de 6,0 x 0,8m, com 4,80m2 de área total, sendo considerada uma área útil de 3,20 m² (0,8 x 4m), eliminando o primeiro metro de cada bordadura. As variáveis foram analisadas de acordo com as características de produção apresentada em campo: Altura média de planta (AMP); Dias até o florescimento (FL); Produção de matéria verde total (PMV); produção de colmo (PCL) e Porcentagem de colmo na produção de matéria verde total (%CL). Além das características agroindustriais: Produção de matéria seca total (PMS); Porcentagem de matéria seca total (%MST); Produção de colmo (PCL); Brix na colheita (BRIX); Eficiência de extração de caldo (EEC) e Etanol teórico (ET). As médias foram comparadas pelo teste de Scott - Knott em nível de 5% de probabilidade, sendo realizada a correlação genotípica para complementar o estudo destas variáveis.

Fatores ambientais e econômicos impulsionam mundialmente a produção de biocombustíveis. No Brasil, o etanol, produzido da cana-de-açúcar, já é um biocombustível estabelecido e substitui ca. 40% da gasolina, representando 13% do total de energia necessária para transportes. Nesse cenário, o Rio Grande do Sul (RS) é um grande comprador de etanol, tendo produzido nos últimos anos apenas 2% do consumo estadual de etanol hidratado combustível. O estado também consome em média 600 milhões de litros de etanol anidro por ano, adicionados na proporção de 25% à gasolina comum, e, a partir de 2010, 460 milhões de litros de etanol por ano para a produção de polietileno verde. Essa conjuntura demonstra uma oportunidade para aumentar a produção local de etanol. O presente trabalho buscou primeiramente avaliar a viabilidade da produção de etanol no Rio Grande do Sul em um modelo de microusinas descentralizadas (ca. 1.000 L.dia-1). Para tanto, foram empregados os indicadores econômicos, como valor presente líquido, taxa interna de retorno de investimento e tempo de retorno de investimento. Foram comparados cenários que empregaram apenas cana-de-açúcar e combinações de cana-de-açúcar, sorgo sacarino, mandioca e batata-doce. A utilização de cana-de-açúcar sem o consórcio com outra cultura se mostrou inviável, exceto quando mais de 40% ou 80% da produção, para as produtividades de 80 e 50 t.ha-1 respectivamente, é destinada ao consumo próprio. Entre os cenários com combinação de culturas, aqueles que combinaram sorgo com cana-de-açúcar e sorgo com batata-doce foram os únicos que se mostraram viáveis quando toda a produção foi destina à venda para terceiros. Quando produtividades médias de cana-de-açúcar próximas a 80 t.ha-1 podem ser alcançadas, verificou-se que a combinação dessa cultura com sorgo sacarino apresentou o melhor potencial entre os cenários avaliados. Já para regiões onde esses valores não são atingidos, o consórcio de sorgo sacarino e batata-doce se mostrou a melhor opção. Posteriormente, foram realizados experimentos em shaker para estudar a influência da concentração de substrato e da proporção de enzima na hidrólise a frio da batata-doce, determinar o melhor pré-tratamento, verificar a necessidade de suplementação do meio e do controle de pH na condução das hidrólises e fermentações simultâneas e finalmente testar a melhor condição em biorreator. Para hidrolisar o amido, empregou a mistura de enzimas Stargen™ 002 e, para suplementar o meio, o fertilizante NITROFOS KL. Em todos os experimentos, usou-se a cultivar BRS Cuia, cuja caracterização indicou teor de carboidratos de 28,7%, possibilitando a produção de 185 L.t-1 de etanol e 7.400 L. ha-1. A metodologia de superfície de resposta indicou a condição 200 g.L-1 de batata-doce e 45 GAU.g de batata–doce-1 como a que apresentou o melhor compromisso entre alta taxa de formação de glicose na primeira hora (8,3 g.L-1.h-1) e baixo consumo de enzimas. O pré-tratamento de uma hora que levou a maior concentração de glicose (14,3 g.L-1) foi na temperatura de 52°C na presença da mistura de enzimas. O estudo da hidrólise e fermentação simultâneas mostrou que a suplementação do meio não apresenta influência significativa, enquanto o controle de pH aumentou em aproximadamente 40% a produção de etanol. Os testes em biorreator reproduziram os resultados anteriores mesmo sendo realizados em ambiente semiestéril, que se aproxima da condição industrial.
In Brazil, sugarcane ethanol is already a reality as a biofuel and replaces 40% of gasoline, meaning 13% of energy for transportation. In this scenario, Rio Grande do Sul has produced only 2% of the annual demand for hydrate ethanol in the last years; therefore it is a big importer of ethanol from other states. Additionally, it consumes every year 600 million liters of anhydrous ethanol mixed in the gasoline and 460 million liters for production of green plastic. These numbers highlight the opportunity of producing ethanol locally. In regard to these facts, the present work aimed to evaluate the feasibility of producing ethanol in small scale plants (ca. 1 000 L.dia-1) in Rio Grande do Sul. For this purpose, economic indicators, such as net present value, internal rate of return and payback period were employed. The compared scenarios involved combinations of sugar cane, sweet sorghum, cassava and sweet potato. When only sugarcane was used, the scenarios for 80 and 50 t.ha-1 were unfeasible if less than 40% or 80% of the production, respectively, was used by the own producer. Regarding the scenarios with mix of crops, the mix of sweet sorghum with sugar cane and sweet sorghum with sweet potato presented the best performances. For regions, where 80 t.ha-1 of sugar cane productivity can be achieved, it was verified that the first combination leads to the best result. For other regions, the combination of sweet sorghum and sweet potato presented itself as the more feasible scenario. As a consequence, in the second part of this work, the cold hydrolysis and fermentation of sweet potato was experimentally studied. For that, it was employed the sweet potato strain BRS Cuia, whose carbohydrate level reaches 28,7%. What it can be translated into a potential to produce 185 L.t-1 ethanol, or equivalently 7 400 L. ha-1. The enzymes blend adopted for the hydrolysis stage was Stargen™ 002, while the fertilizer NITROFOS KL was used for fermentation medium supplementation. The surface response method indicated 200 g.L-1 of sweet potato and 45 GAU.g of sweet potato-1 as the best balance between high glucose formation rate in the first hour (8,3 g.L-1.h-1) and low enzyme consume. The one hour pre-treatment that achieved the highest glucose concentration (14,3 g.L-1) was at 52°C in the presence of the enzymes blend. The study of the simultaneous hydrolysis and fermentation showed that the medium supplementation has no significant effect over the fermentation performance, while the pH control is beneficial, improving the ethanol production in 40%. Finally, the tests in bioreactor could reproduce the previous results, even though the experiments were carried out non-sterilely.

O etanol é utilizado como combustível desde o início do século XX, porém foi a partir da década de 1970 que sua utilização em larga escala foi concretizada pela primeira vez no mundo. Através do PROÁLCOOL foi estabelecido bases para sua produção, distribuição e comercialização. A cultura da cana-de-açúcar prevaleceu em relação às demais como mandioca e babaçu. Análises do potencial do sorgo sacarino também foram realizadas, mas devido ao desconhecimento desta cultura no Brasil não houve muito progresso na sua utilização. No início do século XXI, motivado por razões ambientais e estratégicas, surge o etanol brasileiro como exemplo de utilização de combustíveis alternativos aos derivados do petróleo. A aceitação do veículo com gerenciamento eletrônico para alimentação de combustíveis diferenciados, popularmente denominados de Flex, impulsionou o uso de etanol em território nacional chamando a atenção do mundo. A constatação de mudanças climáticas mundiais despertou a consciência do uso de hidrocarbonetos e suas conseqüências. A expectativa de um mercado mundial de etanol leva a procura de novas fontes de matérias-primas, uma vez que não se pode e não se deve plantar cana-de-açúcar em todos os lugares ou regiões do planeta. Surge o sorgo sacarino como uma das alternativas. Cultura milenar em vários paises demonstra grande potencial para produção de etanol, seguindo os mesmos procedimentos utilizados para cana, porém com menor ciclo de cultivo e menor necessidade hídrica e tolerância ao tipo de terra a ser cultivado. Seu aproveitamento é apoiado pela FAO em diversos paises, entre eles a China. A adoção por parte dos Estados Unidos do etanol em substituição ao metanol e as metas estabelecidas para a adição à gasolina nos próximos anos, provocou um acelerado aumento na produção de etanol, sendo esta baseada em milho. Diversos paises já se espelham nas experiências brasileiras para obtenção de maior independência energética. As necessidades para o abastecimento, dos mercados interno e externo, refletem as iniciativas de investimentos em novos projetos de novas usinas produtoras de etanol. Paises como China, Suécia, Japão já demonstraram amplo interesse na adoção do etanol como aditivo junto à gasolina. As pesquisas em novos sistemas de produção de etanol motivam instituições e empresas a uma busca acelerada para obtenção de processos mais rentáveis e economicamente viáveis.
Ethanol is being used as combustible since the beginning of century XX. However, since the decade of seventy it has been used in large scale in the world. The PROÁLCOOL program established bases for its production, distribution and commercialization. The culture of the sugar cane prevailed in relation to cassava and babaçu. Analyses of the potential of sweet sorghum had been also carried through, but due to the unfamiliarity of this culture in Brazil it did not have much progress in its use. At the beginning of century XXI, motivated for environmental and strategy reasons, Brazilian ethanol appears in the world scenario as an example of use of alternative fuels as substitutes for oil derivatives. The acceptance of vehicles with electronic management for differentiated fuel feeding, known as Flex cars, stimulated the use of ethanol in Brazil calling the attention the world. The knowledge of the worldwide climate changes brought the conscience of the use of hydrocarbons and its consequences. The expectation of a worldwide market of ethanol leads to the search for new sources of fuels. Since sugar cane cannot be planted all over the world due to climate differences, sweet sorghum appears as a promising alternative. Millenarian culture in several countries, it demonstrates a great production potential for the production of ethanol. The same procedures employed for sugar cane can be used. However, the sorghum crops require a lesser cycle of culture and minor water needs and tolerance when compared against sugar cane. Its exploitation is supported by FAO in several countries, being China among them. The adoption of ethanol the United States in substitution to methanol and the goals established for the addition to the gasoline in the next years, has been leading to the increase in the production of ethanol, manufactured from maize. Several countries already have been following the Brazilian path for the attainment of bigger energy independence. The necessities for the supplying of the domestic and external markets reflect the initiatives of investments in new projects of new producing plants of ethanol. Countries such as China, Sweden and Japan already had demonstrated a great interest in the adoption of ethanol as a gasoline additive. The research for new systems of production of ethanol motivates institutions and companies to search for the attainment of more income-producing and economically viable processes.

Dans l'optique de produire des agro‐carburants, le sorgho sucré est aujourd'hui proposé comme une alternative à d'autres espèces cultivées à grande échelle comme la canne à sucre et le maïs car il présente plusieurs avantages : le sorgho est résistant à la sécheresse et à la chaleur, il nécessite peu d'intrants, a en moyenne un cycle de culture relativement court (3‐4 mois) comparé à la canne à sucre. Il offre une grande diversité génétique à explorer et exploiter, tout en étant génétiquement moins complexe que la canne à sucre. Finalement, il peut être cultivé pour un double usage, le grain pouvant être utilisé comme source d'alimentation pour l'homme ou le bétail (à partir du grain) et le jus sucré contenu par les tiges comme source d'agrocarburant. Cette polyvalence en fait une culture idéale pour lutter contre la compétition entre cultures énergétiques et cultures vivrières et assurer des rendements dans des environnements de culture sujets au stress hydrique et thermique comme c'est le cas en Afrique de l'Ouest. Cependant, le caractère sucré du sorgho est complexe, car sous l'influence d'interactions Génotype X Environnement (GxE). Aussi, les mécanismes métaboliques, morphologiques ou phénologiques constituant la cinétique d'accumulation des glucides dans la tige et son éventuelle compétition avec le remplissage des grains restent mal connus ou très controversés dans la littérature. La présente thèse, réalisée dans le cadre du projet européen Sweetfuel, vise à comprendre ces mécanismes, afin de contribuer à la définition d'idéotypes de sorgho double usage, pour les environnements soudano‐sahéliens.Sur la base d'études expérimentales au champ au Mali et en serre en France, il a pu être démontré que les glucides sont accumulés dans les entrenoeuds des tiges par un jeu d'activités enzymatiques (favorisant l'accumulation d'hexoses puis de saccharose) dès le début de leur élongation, donc potentiellement avant la floraison. Au Mali, l'étude au champ de 14 génotypes adaptés aux conditions locales, plus ou moins sensibles à la photopériode et semés à trois dates différentes, a démontré le bénéfice d'un rallongement de la phase végétative sur la quantité de sucre accumulée dans les tiges de la plante à floraison, du fait d'un plus grand nombre d'entrenoeuds allongés et du temps à leur disposition pour accumuler des glucides avant ce stade. Ce bénéfice était cependant plus lié à la plus grande quantité de biomasse accumulée (taille des tiges) qu'à la concentration en sucre dans les entrenoeuds (plutôt stable entre dates de semis).Ainsi, la durée de la phase végétative et la sensibilité à la photopériode sont proposés comme des paramètres clés favorisant la quantité de glucides accumulée dans les tiges de la plante à floraison. D'autre part, il a été montré que la quantité de glucides présente à maturité dans les tiges des mêmes génotypes ne différait pas ou peu de celle à floraison, une éventuelle réduction pour quelques génotypes n'étant généralement pas significative et évitable par l'allongement du cycle. De plus, cette quantité de glucides dans les tiges à maturité n'a tiré aucun bénéfice de l'ablation de la panicule à floraison chez les mêmes génotypes. Ces résultats suggèrent que la compétition entre le remplissage du grain et la production de sucre est faible chez le sorgho, d'autant plus faible que la plante présente de grandes tiges et donc un grand compartiment de stockage des glucides, tamponnant cette éventuelle compétition. D'ailleurs, à une échelle plus fine, aucune différence n'a pu être mise en évidence en termes d'activité des principales enzymes du métabolisme carboné dans la tige d'un génotype dans sa version stérile (pas de remplissage du grain) et fertile.Ce travail a démontré le potentiel du sorgho pour une double utilisation dans un contexte soudano‐sahélien et la pertinence d'exploiter la diversité génétique de cette espèce pour cette objectif de sélection. Les résultats ob
Sweet sorghum offers many advantages as an alternative to widely cultivated crops such as corn and sugarcane to produce biofuels: it is resistant to water stress, it requires few inputs; it has a shorter growth cycle compared to sugarcane in particular. Sorghum also exhibits a great genetic diversity and is genetically less complex than sugarcane. Finally, sorghum can be cultivated for dual‐purpose uses, using grains for food or feed and sweet juice for biofuel production. Hence, sorghum is a promising option to reduce the competition for land and (water) resource use between food and fuel, in particular in cropping environments with high drought and heat stress frequency, as in West Africa. However, stem sweetness is a complex trait prone to genotype x environment interactions (GxE). The metabolic, morphological and phenological mechanisms involved in the kinetic of stem sugar accumulation and its possible competition with grain filling are largely unknown or controversial in the literature. The present work is part of the European project Sweetfuel and aims at better understanding these mechanisms and contributing to define dual‐purpose sorghum ideotypes for soudano‐sahelian conditions.Based on field and greenhouse experiments respectively in Mali and France, it was found that sugars start accumulating in stem internodes at the onset of their elongation, i.e. potentially soon before the plant flowers. The successive accumulation of hexose and then sucrose in internodes could be dynamically explained by changes in the activity of key enzymes related to sucrose metabolism. In Mali, a field experiment performed on 14 genotypes, contrasted for photoperiod sensitivity and sown at three planting dates, highlighted the interest of increasing vegetative phase duration to increase sugar yield. This was explained first of all by the higher number of internodes that could expand during a longer vegetative phase, and thus, by the higher production of stem biomass, and, to a minor extent, by the longer time for internodes to mature and accumulate sugar (sugar concentration in the stem was however fairly stable across sowing dates). Also, vegetative phase duration and photoperiod sensitivity can be considered as two key parameters promoting stem sugar content before grain filling. In the same time, it was shown that stem sugar content kept remarkably constant between anthesis and maturity in most of studied genotypes and that the reduction observed for some genotypes was overcome with an early sowing. Moreover, sugar accumulation in the stem between flowering and maturity did not benefit from panicle pruning. These results together suggest that the competition for carbohydrates between stem sugar reserves and grain filling is weak; it is even weaker for big/large stem genotypes with huge sugar reserves in the stem that would buffer a post‐flowering allocation of sugar from the stem to the grains if required. This low competition was confirmed at a finer scale, as no differences were observed in the activity of key enzymes of sucrose metabolism between the sterile and the fertile line of a same genotype.This work demonstrates the potential of sorghum for dual‐purpose in particular for soudano‐sahelian cropping conditions and the interest of using its genetic diversity for this breeding purpose. It provides further knowledge for revisiting the phenotyping strategies to be adopted to investigate the genetic basis of sugar and grain production and their combination. The results are also currently used to improve the way the source‐sink relationships underlying this dual production are formalized in crop and plant models at CIRAD. Such models will be then useful to assist sorghum ideotype exploration for dual purpose

Sweet sorghum is a highly versatile C4 grass noted for its improved drought tolerance and water use efficiency relative to sugarcane. Sweet sorghum is well suited for ethanol production due to a rapid growth rate, high biomass production, and a wide range of adaptation. Unlike the 12-18 month growth cycle of sugarcane, sweet sorghum produces a harvestable crop in three to five months. Sweet sorghum and sugarcane crops are complementary and in combination can extend the sugar mill seasons in many regions of the world to an estimated 8 months. Seasonal growth and weather patterns both optimize and restrict production of each crop to specific times of the year, however these are different for the two crops. In addition to temporally spacing the date of harvest between crops, the genetic variability of maturity within the crops may also be used to extend the mill seasons; specific hybrids can be used and selected to maximize yield throughout the harvest season. Under favorable growing environments, sweet sorghum hybrids of all maturity groups produced sugar yields ranging from 2.8 to 4.9 MT/ha. Early/medium, late, and very late maturity hybrids planted during April, May, and June planting dates are necessary to maximize the mill season. In this study, early/medium maturity hybrids planted during April and May matured for harvest between late July and mid-August. June planting dates were unfavorable for early/medium maturity hybrids. In addition, late and very late maturity hybrids planted during April matured for harvest in late August; the additional growing season thus resulted in higher sugar yields. Timely planting of late and very late maturity hybrids in April, May, and June produce the maximum yields for harvests after mid August. Intermittent use of late and very late maturity hybrids can therefore extend sugar milling seasons into mid November if so desired.