Sugarcane straw as a feedstock for xylitol production by Candida guilliermondii FTI 20037

Sugarcane straw has become an available lignocellulosic biomass since the progressive introduction of the non-burning harvest in Brazil. Besides keeping this biomass in the field, it can be used as a feedstock in thermochemical or biochemical conversion processes. This makes feasible its incorporation in a biorefinery, whose economic profitability could be supported by integrated production of low-value biofuels and high-value chemicals, e.g., xylitol, which has important industrial and clinical applications. Herein, biotechnological production of xylitol is presented as a possible route for the valorization of sugarcane straw and its incorporation in a biorefinery. Nutritional supplementation of the sugarcane straw hemicellulosic hydrolyzate as a function of initial oxygen availability was studied in batch fermentation of Candida guilliermondii FTI 20037. The nutritional supplementation conditions evaluated were: no supplementation; supplementation with (NH4)2SO4, and full supplementation with (NH4)2SO4, rice bran extract and CaCl2·2H2O. Experiments were performed at pH 5.5, 30 °C, 200 rpm, for 48 h in 125 mL Erlenmeyer flasks containing either 25 or 50 mL of medium in order to vary initial oxygen availability. Without supplementation, complete consumption of glucose and partial consumption of xylose were observed. In this condition the maximum xylitol yield (0.67 g g-1) was obtained under reduced initial oxygen availability. Nutritional supplementation increased xylose consumption and xylitol production by up to 200% and 240%, respectively. The maximum xylitol volumetric productivity (0.34 g L-1 h-1) was reached at full supplementation and increased initial oxygen availability. The results demonstrated a combined effect of nutritional supplementation and initial oxygen availability on xylitol production from sugarcane straw hemicellulosic hydrolyzate.(AU)

Produção de etanol a partir de mosto hidrolisado hemicelulósico de ponta e palha de cana-de-açúcar

A utilização de diferentes biomassas vegetais como fonte de energia renovável deve contribuir para a redução do uso de combustíveis fósseis, minimizando impactos negativos ao meio ambiente. Como resultado direto da colheita mecanizada da cana, tem-se o aumento de ponteiros e palha nos canaviais, insumo de grande potencial energético que podem ser utilizados para a produção do etanol de segunda geração, aumentando a produção anual de etanol sem acréscimos em áreas de plantio. A hidrólise deste material, torna disponível os açúcares constituintes das frações celulósicas e hemicelulósicas e deve passar por um processo de destoxificação para redução do teor de inibidores provenientes da etapa de hidrólise. Neste estudo objetivou-se avaliar o mosto de hidrolisado hemicelulósico de folhas e ponteiros de cana, em comparação com mosto de caldo de cana, fermentado por leveduras que desdobram hexoses e pentoses para produção de etanol de segunda geração. Os mostos foram compostos por caldo de cana, hidrolisado hemicelulósico de folhas e pontas de cana e pela mistura destes dois mostos (50%). O processo fermentativo foi realizado em escala laboratorial empregando-se as estirpes J10 e FT858 de leveduras e a mistura destas (50%). Foram feitas análises de viabilidade celular e índice de brotamentos e avaliadas as concentrações dos açúcares e produção de etanol. A viabilidade celular, viabilidade de brotos e o brotamento sempre foram maiores em mosto de caldo de cana. Os valores mais elevados entre as leveduras foram obtidos pela linhagem J10. O processo de destoxificação utilizado promoveu uma remoção parcial de ácidos e composto fenólicos. A utilização de coculturas de microrganismos foi mais eficiente na produção de etanol em relação as culturas individuais. O hridrolisado hemicelulósico apresentou baixa eficiência na produção de etanol

The use of different plant biomass as a renewable energy source should contribute to reducing the use of fossil fuels, minimizing negative impacts to the environment. As a direct result of mechanical harvesting of sugarcane has increased pointers and straw in the cane fields, input of large energy potential that can be used for the production of second generation ethanol, increasing the annual production of ethanol without increases in areas planting. Hydrolysis of this material makes available the sugars constituting the cellulose and hemicellulose fractions and must undergo a detoxification process for reducing the content of inhibitors from the hydrolysis step. This study aimed to evaluate the wort hemicellulosic hydrolyzate pointers leaves and cane, compared with mash of sugar cane juice, fermented by yeasts that unfold hexoses and pentoses for production of second generation ethanol. The musts were composed of sugarcane juice, hemicellulosic hydrolyzate leaves and cane tips and the mixture of these two musts (50%). The fermentation was performed in laboratory scale employing strains J10 and FT858 yeast and mixing these (50%). Analyzes were performed for cell viability and budding index and evaluated the concentrations of sugars and ethanol production. Cell viability, feasibility and budding shoots were always higher in mash of sugar cane juice. The highest values were obtained between the yeast strain J10. The detoxification process used promoted partial removal of acids and phenolic compounds. The use of cocultures of microorganisms was more efficient in producing ethanol in relation to individual cultures. The hemicellulosic hridrolisado showed low efficiency in ethanol production