多级串联悬浮床反应器系统中自絮凝颗粒酵母乙醇连续发酵耦合废糟液直接全循环使用的研究

在一套四级串联悬浮床生物反应器系统中，以双酶法制备的玉米粉糖化液为底物，进行了废糟液全循环条件下自絮凝颗粒酵母乙醇连续发酵的实验研究。在实验中，每隔5 d将从末级反应器收集到的发酵液集中精馏处理，得到的废糟液直接用于玉米粉调浆制糖。系统连续运行了120d，共进行了24批次实验，数据分析表明系统达到了平衡状态。在平均发酵时间为20h条件下，发酵终点乙醇浓度平均为11.7%（V/V），残还原糖浓度平均为7.9g/L，装置运行平稳。这些工作为自絮凝颗粒酵母乙醇发酵耦合废糟液直接全循环使用、实现污染物源头减废、清洁生产奠定了理论和实验基础。

Continuous Ethanol Fermentation Using Self-flocculating Yeast in Multistage Suspended Bioreactors Coupled with Directly Recycling of Waste Distillage

A fermentation system composed of four airlift suspended-bed bioreactors in series and with a total working volume of 4800 mL was established. Continuous ethanol fermentation using self-flocculating yeast SPSC01, a fusant from Saccharomyces cerevisiae and Schizosaccharomyces pombe, and two-stage enzymatic hydrolyte of dry milling corn powder, was continuously run for 120 days. All of the backset distillage collected after distilling the final beer was used to mix the corn powder and no any other wastes except the solid residue of corn powder was discharged from the fermentation system, which guaranteed the distillage to be recycled at its maximum. The experimental results revealed that both ethanol and residual sugar in the final beer could be maintained relatively stable with their average levels of 93.6 and 7.9 g/L, respectively when the fermentation system was operated at the dilution rate of 0.05 h~ -1. Parameter oscillations reported previously were also observed for the first and second bioreactors, but were effectively attenuated thereafter, which indicated that high yeast cell concentrations resulted from the self-immobilization of this special self-flocculating strain contributed to damp these oscillations. The monitoring of residual nitrogen and phosphor indicated that the accumulations of these nutritional elements occurred and the amount of these inorganic salts supplemented in the substrate should be decreased properly.