Novel dihydrogen-bonding deep eutectic solvents: Pretreatment of rice straw for butanol fermentation featuring enzyme recycling and high solvent yield

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2018-02, Vol.333, p.712-720
• Main Authors: Xing, Wanru, Xu, Guochao, Dong, Jinjun, Han, Ruizhi, Ni, Ye
• Format: Article
• Language: English
• Subjects: Butanol; Deep eutectic solvent; Enzyme recycle; Pretreatment; Rice straw
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2017.09.176

[Display omitted] •DES was synthesized with choline chloride and double hydrogen bond donors.•A two-stage pretreatment was developed with total sugar of 42.8 g·L−1.•Cellulase dosage was reduced for 40% in 5 continuous enzyme recycle.•Butanol titer of 9.5 g·L−1 was achieved with rice straw hydrolysates. Rice straw (RS) is one of the most abundant lignocellulosic biomasses in China, which contains mainly of cellulose, hemicellulose and lignin. In this study, a novel deep eutectic solvent (DES), foraceline, was prepared with choline chloride and double hydrogen bond donors (formic acid and acetic acid). By combining foraceline and sodium carbonate (1%), a two-stage pretreatment method was developed and applied in RS pretreatment to improve the biodegradability of lignocellulose. The highest glucose and total sugar of 37.3 g·L−1 and 42.8 g·L−1 were obtained after hydrolysis of 24 h using 50 FPU·gtotal solid-1 of cellulase. The cellulase attached to RS was reutilized for five continuous cycles in which enzyme loading was reduced from 50 FPU·gtotal solid-1 (Cycle I) to 30 FPU·gtotal solid-1 (Cycle V), resulting in total sugar of 41.3–42.6 g·L−1 for each cycle. RS hydrolysates (Cycle I and V) was utilized in butanol fermentation by Clostridium saccharobutylicum DSM 13864, achieving butanol titer and yield of 9.5 g·L−1 and 0.25 g·gtotal sugar-1, similar to those of glucose medium. This study demonstrated the feasibility of this newly developed biomass pretreatment by dihydrogen bonding DES featuring cellulase recycling and high butanol yield.