Simultaneous liquefaction, saccharification, and fermentation (SLSF) has attracted much attention for the production of bio-based chemicals, including L-lactic acid, due to its high efficiency and low cost. In this study, a lactic acid-producing bacterium with high tolerance of temperature up to 55 °C was isolated and characterized as Enterococcus faecalis DUT1805. Various strategies of stepwise controlled temperature were proposed and investigated for glucose utilization. The results indicated that E. faecalis DUT 1805 exhibited an optimal temperature at 50 °C, which could achieve temperature compatibility of enzyme, saccharification, and fermentation, and decrease the possibility of contamination by the other microorganisms during the large-scale fermentation. To reduce the cost of raw material and operation for lactic acid production, aging paddy rice with hull (APRH) was used in L-lactic acid production by simultaneous liquefaction, saccharification, and fermentation (SLSF). An open SLSF operation at 50 °C and pH 6.5, and 17% (w/v) solid loading in 5 L bioreactors was demonstrated with the lactic acid titer, yield, and productivity of 73.75 g/L, 87% to initial starch, and 2.17 g/(L h), respectively.

中文翻译：

---

通过分离的耐热肠球菌DUT1805，使用带有外壳的老化稻谷，同时液化，糖化和发酵L-乳酸。

同时液化，糖化和发酵（SLSF）由于其高效和低成本而在生产基于生物的化学品（包括L-乳酸）方面引起了广泛的关注。在这项研究中，分离出具有最高55°C温度耐受性的产乳酸细菌，并将其表征为粪肠球菌DUT1805。提出了逐步控制温度的各种策略，并研究了其对葡萄糖的利用。结果表明，粪肠球菌DUT 1805在50°C时具有最佳温度，可以实现酶，糖化和发酵的温度相容性，并减少大规模发酵过程中被其他微生物污染的可能性。为了降低乳酸生产的原材料和生产成本，通过同时液化，糖化和发酵（SLSF）将老化的带壳稻米（APRH）用于生产L-乳酸。在50°C，pH 6.5和5 L生物反应器中固体载量为17％（w / v）的条件下进行的开放式SLSF操作证明，乳酸滴定度，产率和生产率为73.75 g / L，相对于初始淀粉为87％，和2.17 g /（L h）。