339 / 2018-07-31 10:22:35

Bioethanol production from wheat straw by phosphoric acid plus hydrogen peroxide (PHP) pretreatment via simultaneous saccharification and fermentation (SSF) at high solid loadings

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In order to make the downstream ethanol production cost-efficient in the lignocellulose biorefinery, a new developed phosphoric acid plus hydrogen peroxide (PHP) pretreatment was employed on wheat straw for ethanol conversion by simultaneous saccharification and fermentation (SSF) at high loadings. Results showed PHP pretreatment could efficiently remove all the hemicellulose and most lignin (70.8%) from wheat straw, while a high yield (97.8%) of cellulose was recovered in the solid fraction, which benefited the subsequent SSF at high solid loadings with relatively low enzyme and yeast input. Solid loading of PHP-pretreated wheat straw can be greatly promoted to 20% when SSF was conducted. Although higher enzyme input significantly improved ethanol conversion, the enzyme usage could still be reduced to 10-20 mg protein/g cellulose with considerable high ethanol conversion. Increasing yeast input also promoted ethanol conversion, however, the responses were not significant. Besides, SSF conditions was optimized by Response surface method for further reducing cost of ethanol production. Minimizing enzyme and yeast input was designed for SSF with the goals of maximizing ethanol conversion and titer. Rather high ethanol conversion of 88.2% and ethanol titer of 69.9 g/L were obtained after 120 h SSF at solid loading of 15.3% with rather low CTec2 enzyme and yeast input (13.2 mg protein/g cellulose and 1.0 g/L, respectively). Consequently, 15.5 g ethanol was harvested from 100 g (dry basis) wheat straw at the optimal conditions with only 1.8 mL enzyme preparation and 0.264 g yeast respectively, suggesting high potential of PHP pretreatment for ethanol production at high solid loadings.