Effective Saccharification of Corn Stover Using Low-Liquid Aqueous Ammonia Pretreatment and Enzymatic Hydrolysis.

Low-liquid aqueous ammonia (LLAA) pretreatment using aqueous ammonia was investigated to enhance enzymatic saccharification of corn stover. In this method, ground corn stover was simply contacted with aqueous ammonia mist (ammoniation step), followed by pretreatment at elevated temperature (90⁻150 °C) for an extended period (24⁻120 h) at different solid/liquid (S/L) ratios (0.29, 0.47 or 0.67), termed a pretreatment step. After that, excess (unreacted) ammonia was removed by evaporation, and the pretreated material was immediately saccharified by an enzyme without a washing step. The effects of key reaction parameters on both glucan digestibility and XMG digestibility were evaluated by analysis of variance (ANOVA). Under the best pretreatment conditions [S/L = 0.47, 0.16 (g NH3)/(g biomass), 90 °C, 24 h], LLAA pretreatment enhanced enzymatic digestibility from 23.1% for glucan and 11.3% for XMG (xylan + galactan + mannan) of untreated corn stover to 91.8% for glucan and 72.6% for XMG in pretreated solid.

Metabolic Engineering for the Comprehensive Utilization of N,N-Dimethylformamide-Containing Wastewater.

N, N-dimethylformamide is frequently present in industrial wastewater and is environmentally detrimental. The current study aims to assess the utilization and biodegradation of N, N-dimethylformamide-containing wastewater to lessen the associated environmental load. Results show that addition of wastewater containing N, N-dimethylformamide to Trichoderma reesei fermentation media enhances cellulase production and facilitates cellulose hydrolysis. However, N, N-dimethylformamide is a cellulase enhancer that is not degraded during cellulase production in T. reesei fermentation and is retained in the N, N-dimethylformamide-enhanced cellulase solution. Indeed, the cellulosic sugar solution generated via lignocellulose hydrolysis with N, N-dimethylformamide-enhanced cellulase retains N, N-dimethylformamide. We further identified three core enzyme modules─N, N-dimethylformamidase, dimethylamine dehydrogenase, and methylamine dehydrogenase enzyme─which were inserted into Escherichia coli to develop metabolically engineered strains. These strains degraded N, N-dimethylformamide and produced succinate using N, N-dimethylformamide-enhanced cellulosic sugar as the substrate. The platform described here can be applied to effectively convert waste into valuable bioproducts.