Biohydrogen production by deep eutectic solvent delignification-driven enzymatic hydrolysis and photo-fermentation: Effect of liquid–solid ratio

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Deep eutectic solvent (DES), a new green solvent, was used to pretreat corncob to enhance biohydrogen production. As a result of the pretreatment, lignin was effectively removed, and the maximum delignification efficiency of 83.12% was achieved. Moreover, the contents of cellulose in the pretreated corncob significantly increased. DES pretreatment effect improved with increasing liquid-solid ratio. The pretreated corncob's enzymatic saccharification activity and hydrogen production were promoted due to the lower content of lignin. The best result was observed at a ratio of 25:1 (DES:corncob, g/g), in which the reducing sugar concentration (53.91 g/L) and the hydrogen yield (151 mL/g) was 6.8 and 3.1 times than that of untreated corncob, respectively. In addition, the lag time of hydrogen production was obviously shortened to 16.53 h due to the utilization of abundant available fermentable sugars, which accelerated hydrogen production.