Hybrid SSF/SHF Processing of SO₂ Pretreated Wheat Straw—Tuning Co-fermentation by Yeast Inoculum Size and Hydrolysis Time

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• 作者：B. Cassells ; K. Karhumaa ; V. Sànchez i Nogué…
• 关键词：Bioethanol ; Xylose fermentation ; SSF ; Yeast inoculum size ; In situ detoxification
• 刊名：Applied Biochemistry and Biotechnology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：181
• 期：2
• 页码：536-547
• 全文大小：647KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Biotechnology; Biochemistry, general;
• 出版者：Springer US
• ISSN：1559-0291
• 卷排序：181

文摘

Wheat straw is one of the main agricultural residues of interest for bioethanol production. This work examines conversion of steam-pretreated wheat straw (using SO₂ as a catalyst) in a hybrid process consisting of a short enzymatic prehydrolysis step and a subsequent simultaneous saccharification and fermentation (SSF) step with a xylose-fermenting strain of Saccharomyces cerevisiae. A successful process requires a balanced design of reaction time and temperature in the prehydrolysis step and yeast inoculum size and temperature in the SSF step. The pretreated material obtained after steam pretreatment at 210 °C for 5 min using 2.5 % SO₂ (based on moisture content) showed a very good enzymatic digestibility at 45 °C but clearly lower at 30 °C. Furthermore, the pretreatment liquid was found to be rather inhibitory to the yeast, partly due to a furfural content of more than 3 g/L. The effect of varying the yeast inoculum size in this medium was assessed, and at a yeast inoculum size of 4 g/L, a complete conversion of glucose and a 90 % conversion of xylose were obtained within 50 h. An ethanol yield (based on the glucan and xylan in the pretreated material) of 0.39 g/g was achieved for a process with this yeast inoculum size in a hybrid process (10 % water-insoluble solid (WIS)) with 4 h prehydrolysis time and a total process time of 96 h. The obtained xylose conversion was 95 %. A longer prehydrolysis time or a lower yeast inoculum size resulted in incomplete xylose conversion.