Gong Zhiwei, Wang Xuemin, Yuan Wei, Wang Yanan, Zhou Wenting, Wang Guanghui, Liu Yi
1School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, 947 Heping Road, Wuhan, 430081 People's Republic of China.
3HuBei Province Key Laboratory of Coal Conversion and New Carbon Materials, Wuhan University of Science and Technology, Wuhan, 430081 People's Republic of China.
Biotechnol Biofuels. 2020 Jan 22;13:13. doi: 10.1186/s13068-019-1639-9. eCollection 2020.
Lignocellulosic biomass has been commonly regarded as a potential feedstock for the production of biofuels and biochemicals. High sugar yields and the complete bioconversion of all the lignocellulosic sugars into valuable products are attractive for the utilization of lignocelluloses. It is essential to pretreat and hydrolyze lignocelluloses at high solids loadings during industrial processes, which is more economical and environmentally friendly as capital cost, energy consumption, and water usage can be reduced. However, oligosaccharides are inevitably released during the high solids loading enzymatic hydrolysis and they are more recalcitrant than monosaccharides for microorganisms.
A fed-batch enzymatic hydrolysis of corn stover pretreated by the sodium hydroxide-methanol solution (SMs) at high solids loading was demonstrated to reach the high concentrations and yields of fermentable sugars. Glucose, xylose, cello-oligosaccharides, and xylo-oligosaccharides achieved 146.7 g/L, 58.7 g/L, 15.6 g/L, and 24.7 g/L, respectively, when the fed-batch hydrolysis was started at 12% (w/v) solids loading, and 7% fresh substrate and a standardized blend of cellulase, β-glucosidase, and hemicellulase were fed consecutively at 3, 6, 24, and 48 h to achieve a final solids loading of 40% (w/v). The total conversion of glucan and xylan reached 89.5% and 88.5%, respectively, when the oligosaccharides were taken into account. Then, a fed-batch culture on the hydrolysates was investigated for lipid production by . Biomass, lipid content, and lipid yield were 50.7 g/L, 61.7%, and 0.18 g/g, respectively. The overall consumptions of cello-oligosaccharides and xylo-oligosaccharides reached 74.1% and 68.2%, respectively.
High sugars concentrations and yields were achieved when the enzyme blend was supplemented simultaneously with the substrate at each time point of feeding during the fed-batch enzymatic hydrolysis. Oligosaccharides were co-utilized with monosaccharides during the fed-batch culture of . These results provide a promising strategy to hydrolyze alkaline organosolv-pretreated corn stover into fermentable sugars with high concentrations and yields for microbial lipid production.
木质纤维素生物质通常被视为生产生物燃料和生物化学品的潜在原料。高糖产量以及将所有木质纤维素糖完全生物转化为有价值的产品对木质纤维素的利用具有吸引力。在工业过程中，在高固含量下对木质纤维素进行预处理和水解至关重要，因为这样可以降低资本成本、能源消耗和用水量，从而更经济且环保。然而，在高固含量酶水解过程中不可避免地会释放出低聚糖，并且它们对微生物而言比单糖更难降解。
证明了在高固含量下对经氢氧化钠 - 甲醇溶液（SMs）预处理的玉米秸秆进行补料分批酶水解可达到高浓度和高产量的可发酵糖。当补料分批水解在12%（w/v）固含量下开始时，葡萄糖、木糖、纤维寡糖和木寡糖分别达到146.7 g/L、58.7 g/L、15.6 g/L和24.7 g/L，并且在3、6、24和48小时连续加入7%的新鲜底物以及纤维素酶、β - 葡萄糖苷酶和半纤维素酶的标准化混合物，以达到40%（w/v）的最终固含量。当考虑低聚糖时，葡聚糖和木聚糖的总转化率分别达到89.5%和88.5%。然后，研究了对水解产物进行补料分批培养以用于[具体微生物]产脂。生物量、脂质含量和脂质产量分别为50.7 g/L、61.7%和0.18 g/g。纤维寡糖和木寡糖的总消耗量分别达到74.1%和68.2%。
在补料分批酶水解过程中，在每个补料时间点将酶混合物与底物同时添加时，可实现高糖浓度和高产量。在[具体微生物]的补料分批培养过程中，低聚糖与单糖被共同利用。这些结果为将碱性有机溶剂预处理的玉米秸秆水解为高浓度和高产量的可发酵糖以用于微生物产脂提供了一种有前景的策略。
