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Integrated hydrolysation and fermentation of the sugar beet pulp to bioethanol

Sugar beet pulp is an abundant industrial waste material which holds a great potential for bioethanol production due to its high content of cellulose, hemicelluloses and pectin. Its structural and chemical robustness limits the yield of fermentable sugars obtained by hydrolysation and represents the main bottleneck for bioethanol production. Physical (ultrasound and thermal) pre-treatment methods were tested and combined with enzymatic hydrolysis by cellulase and pectinase to evaluate the most efficient strategy. The optimized hydrolysis process was combined with a fermentative step using a Saccharomyces cerevisiae strain for ethanol production in a single tank bioreactor. Optimal sugar beet pulp conversion was achieved at a concentration of 60 g/l (39% of dry weight) and a bioreactor stirrer speed of 960 rpm. The maximum ethanol yield was 0.1 g ethanol/g of dry weight (0.25 g ethanol/g total sugar content), the efficiency of ethanol production was 49% and the productivity of the bioprocess was 0.29 g/l·h, respectively.

sugar beet pulp; bioethanol; ultrasound pretreatment; thermal pretreatment; enzymatic hydrolysis; Saccharomyces cerevisiae

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