Data for A Chemical-Free Pretreatment for Biosynthesis of Bioethanol and Lipids from Lignocellulosic Biomass: An Industrially Relevant 2G Biorefinery Approach

A wide range of inorganic and organic chemicals are used during the pretreatment and enzymatic hydrolysis of lignocellulosic biomass to produce biofuels. Developing an industrially relevant 2G biorefinery process using such chemicals is challenging and requires more unit operations for downstream processing. A sustainable process has been developed to achieve industrially relevant titers of bioethanol with significant ethanol yield. The pretreatment of sorghum biomass was performed by a continuous pilot-scale hydrothermal reactor followed by disk milling. Enzymatic hydrolysis was performed without washing the pretreated biomass. Moreover, citrate buffer strength was reduced to 100-fold (50 mM to 0.5 mM) during the enzymatic hydrolysis. Enzymatic hydrolysis at 0.5 mM citrate buffer strength showed that significant sugar concentrations of 222 ± 2.3 to 241 ± 2.3 g/L (glucose + xylose) were attained at higher solids loadings of 50 to 60% (w/v). Furthermore, hydrolysates were fermented to produce bioethanol using two different xylose-fermenting Saccharomyces cerevisiae strains and a co-culture of xylose-fermenting and non-GMO yeast cultures. Bioethanol titer of 81.7 g/L was achieved with an ethanol yield of 0.48 gp/gs. Additionally, lipids were produced using the oleaginous yeast Rhodosporidium toruloides, yielding 13.2 g/L lipids with cellular lipid accumulation of 38.5% w/w from 100 g/L of sugar concentration. In summary, reducing the strength of the citrate buffer during enzymatic hydrolysis and omitting inorganic chemicals from the pretreatment process enhances the fermentability of hydrolysates and can also reduce operating costs.

为制备生物燃料，木质纤维素生物质的预处理与酶解过程中需使用多种无机与有机化学品。采用此类化学品构建工业化级第二代（2G）生物炼制工艺颇具挑战，且下游处理需增设更多单元操作。本研究开发了一种可持续工艺，可实现具备可观乙醇得率的工业化级生物乙醇效价。本研究采用连续式中试规模水热反应器对高粱生物质进行预处理，随后辅以圆盘粉碎工艺，且无需对预处理后的生物质进行水洗即可开展酶解反应。此外，酶解过程中柠檬酸盐缓冲液的浓度被降低至原浓度的1/100（由50 mM降至0.5 mM）。在0.5 mM柠檬酸盐缓冲液条件下进行的酶解实验显示，当固形物含量为50%~60%（w/v）的高固体系中，可获得222±2.3至241±2.3 g/L的总糖浓度（葡萄糖+木糖）。此外，本研究采用两株不同的木糖发酵酿酒酵母（Saccharomyces cerevisiae）菌株，以及木糖发酵酵母与非转基因酵母的共培养体系，对酶解液进行发酵以制备生物乙醇，最终获得81.7 g/L的生物乙醇效价，乙醇得率达0.48 gp/gs。此外，本研究利用产油酵母红冬孢酵母（Rhodosporidium toruloides）以100 g/L的糖浓度为底物制备油脂，最终获得13.2 g/L的油脂产量，细胞内脂质积累量达38.5%（w/w）。综上，在酶解过程中降低柠檬酸盐缓冲液浓度、并在预处理工序中省去无机化学品的使用，可提升酶解液的发酵性能，同时降低运营成本。