Production of 2,3-butanediol from acid hydrolysates of Jatropha hulls with Klebsiella oxytoca

Jatropha hulls were successfully for the first time used as raw materials for the production of 2,3-butanediol via dilute sulfuric acid hydrolysis and fermentation with Klebsiella oxytoca. Two-step hydrolysis was used to effectively hydrolyze the hulls at 150 °C after pretreatment. In the first-step, hemicellulose was hydrolyzed under mild conditions (0.5 h, 1.5% acid) to avoid secondary decomposition. The remained cellulose was further hydrolyzed in the second-step under severer conditions (1 h, 4% acid). After hydrolysis, total hydrolysis yield was 64%, which was much higher than that (37%) from the first-step. Maximum yields of 2,3-butanediol and acetoin in flask experiments were 35.6% and 41.4% from the hydrolysates of the first- and second-step hydrolysis, equivalent to 71.2% and 82.8% of the theoretical values, respectively. Similar yields were obtained in a controlled bioreactor but with higher productivities. Jatropha hulls are attractive raw materials for the production of 2,3-butanediol with high yield.