Pretreatment of corn stover by solid acid for d-lactic acid fermentation

Solid acid is a new acid that is safe and green, which has been widely used in the fields of acid pickling. In this study, we adopted solid acid to pretreat corn stover and used the pretreated corn stover in the fermentation of d-lactic acid. Finally, we obtained optimal conditions for the pretreatment of corn stover by solid acid: digestion temperature of 120 °C, digestion time of 80 min, and solid acid concentration of 1.5%. Then adding cellulase of 30 FPU/g, the conversion rate of glucose reached 71.06% after enzymatic hydrolysis for 72 h. In addition, the changes of corn stover structure after pretreatment were further represented by using scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). At the same time, we used the pretreated corn stover as fermentation substrate and Lactobacillus. delbrueckii sp. bulgaricus as the starting strain to produce d-lactic acid. The yield reached 18 g/L, with the optical purity being 99%e.e. This research has provided a new way to comprehensively utilizae corn stover.