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利用发酵性能优良的自絮凝酵母Saccharomyces cerevisiaeflo,研究开发了重复批次高浓度乙醇发酵系统,以节省下游加工过程的能耗。在终点乙醇浓度达到120g/L左右的条件下,发酵系统的乙醇生产强度达到8.2g/(L·h)。然而实验中发现,随着发酵批次的增多,自絮凝酵母沉降性能逐渐下降,从发酵液中沉降分离所需时间相应延长,导致发酵液中高浓度乙醇对酵母的毒害作用加剧,影响其发酵活性和发酵系统运行的稳定性,发酵装置运行11个批次后无法继续运行。实验结果表明,絮凝能力下降导致的酵母絮凝颗粒尺度减小是其沉降性能下降的主要原因。进一步研究发现,酵母的絮凝能力通过再培养可以恢复。在此基础上对发酵系统操作进行改进,每批发酵结束后可控采出一定比例菌体,调节系统的酵母细胞密度和乙醇生产强度以刺激酵母增殖,保持其絮凝能力。在达到相同发酵终点乙醇浓度条件下,虽然发酵系统的乙醇生产强度降低到4.0g/(L·h),但运行10d后絮凝颗粒酵母尺度趋于稳定,继续运行14d,未发现絮凝颗粒酵母尺度继续下降的现象,系统可以稳定运行。
Using the self-flocculating yeast Saccharomyces cerevisiaeflo, which has excellent fermenting performance, a batch of high-concentration ethanol fermentation system was developed to save the energy consumption of downstream processing. Under the conditions of the final ethanol concentration reaching 120g / L, the ethanol production intensity of the fermentation system reached 8.2g / (L · h). However, it was found in the experiment that the settling performance of the self-flocculating yeast decreased gradually with the increase of fermentation batches, and the time required for sedimentation and separation from the fermentation broth was correspondingly prolonged, resulting in the aggravating effect of high concentration ethanol in the fermentation broth on the yeast and affecting the fermentation activity And the stability of the fermentation system operation, the fermentation unit can not continue operation after running 11 batches. The experimental results show that the reduction of flocculation particle size caused by the decrease of flocculation capacity is the main reason for the decrease of sedimentation performance. Further research found that yeast flocculation ability can be restored by re-culture. On this basis, the operation of the fermentation system is improved. After each batch of fermentation, a certain proportion of the bacterial cells can be controlled and controlled to adjust the yeast cell density and the ethanol production intensity to stimulate the yeast proliferation and maintain its flocculation capacity. At the same fermentation endpoint ethanol concentration, the flocculation particle size tended to be stable after 10 days of operation, and continued to run for 14 days. No flocculated particle size was observed Continue to decline phenomenon, the system can be stable operation.