Sunday, May 4, 2008
3-40

Optimizing the hydrolysis of sugarcane bagasse hemicellulose with dilute H2SO4 through empirical modeling: An experimental approach to increase the yield of xylose recovery

Larissa Canilha1, Walter Carvalho2, George Jackson Moraes Rocha2, Marias das Graças Almeida Felipe2, João Batista Almeida e Silva2, and Marco Giulietti1. (1) Chemical Division, Institute of Technological Research, São Paulo, Brazil, (2) Department of Biotechnology, Engineering College of Lorena-University of São Paulo, Lorena, Brazil

Dilute-acid hydrolysis has frequently been used to hydrolyze the hemicelluloses of many lignocellulosic materials, leading to xylose-rich hydrolysates that can be used for the production of goods like xylitol and ethanol. In the present study, experiments based in a 23 central composite full factorial design were carried out in 200 mL stainless steel containers in order to improve the yield of xylose recovery from the sugarcane bagasse hemicellulose (YX/B). The temperature (A), the sulfuric acid concentration (B) and the residence time (C) were considered as the independent variables, while the YX/B was taken as the response variable. Bagasse loading of 15 % (dry-mass basis) was used in all the experiments. According to the results, all the three independent variables influenced the YX/B significantly (p < 0.05). A quadratic model, YX/B = 57.09 + 8.89 B + 11.26 C – 7.16 B2 – 9.89 C2, was developed to correlate the response variable with both the acid concentration and the residence time, maintaining the temperature at 150 °C. According to the aforementioned model, an YX/B of 54.4 - 71.1 % of the maximum theoretical value would be obtained by performing the hydrolysis at 2.0 % (w/v) acid concentration and 28 min. Such prediction was further confirmed by an additional hydrolysis at the optimum conditions, an YX/B of 57.3 % being obtained. This hydrolysate presented a high xylose concentration (33.2 g/L), which would reduce the necessity to increase the substrate content by vacuum concentration prior to the subsequent fermentation.
ACKNOWLEDGEMENTS: FAPESP and CNPq (Brazil)

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