Enhancement of biomass conservation and enzymatic hydrolysis of rice straw by dilute acid-assisted ensiling pretreatment.

To reduce the cost of lignocellulosic pretreatment, rice straw was ensiled with dilute formic acid (FA, 0, 0.2, 0.4, and 0.6%) for 3, 6, 9, 15 and 30 days, and evaluated its effects on fermentation dynamics, lignocellulosic degradation and enzymatic hydrolysis. The results showed that the application of FA, especially at 0.6% level, reduced total fermentation losses of the resulting silages, as evidenced by low dry matter loss, ammonia nitrogen and ethanol content. Meanwhile, the 0.6% FA application promoted hemicellulose removal (232.41 vs 187.52 g/kg DM) and xylose production (0.35 vs 2.80 g/kg DM). The glucose yield and cellulose convertibility of rice straw increased after 30 days of ensiling, and further enhanced by the 0.6% FA application. In conclusion, the 0.6% FA-assisted ensiling pretreatment improved both biomass preservation, hemicellulose removal and enzymatic hydrolysis of rice straw, which is beneficial to the subsequent biofuel production chain.