絮凝颗粒粒度分布对自絮凝酵母SPSC01乙醇耐受能力的影响
首发时间：2007-05-18
摘要：利用激光聚焦反射式颗粒测量系统，通过调节不同的搅拌速率，得到了补料分批培养条件下粒度分布不同的四个絮凝酵母SPSC01颗粒群体，进而对絮凝颗粒群体分布对乙醇耐受性进行了系统研究。经过6 h、20%乙醇的冲击，颗粒粒度为100 、200、300和400 μm的自絮凝酵母SPSC01的存活率分别为3.5%、26.7%、48.8%和37.6%，这表明不同粒度分布的絮凝颗粒群体乙醇耐受性具有明显差别，在一定粒度范围内乙醇耐受性达到最高，乙醇耐受性最高的酵母群体的乙醇得率系数比乙醇耐性最低的颗粒群体提高了7.2%。粒度为100、200和300 μm的自絮凝酵母颗粒群体总麦角固醇、游离麦角固醇及海藻糖含量与粒度大小成正相关，但在粒度为400 μm的絮凝颗粒群体中总麦角固醇、游离麦角固醇及海藻糖含量呈下降趋势，与其乙醇耐性低于300 μm絮凝颗粒的结果相一致。对细胞膜透性的研究表明，颗粒粒度为300 μm的絮凝酵母颗粒细胞膜通透性（P′）最低，分别仅为颗粒粒度为100 μm和200 μm颗粒群体的43%和52%，表明粒度分布不同的絮凝颗粒群体乙醇耐性的差别与细胞膜透性密切相关。研究结果表明，絮凝酵母不同颗粒大小的体系存在差别明显的生化合成活性，絮凝酵母的乙醇耐性强的颗粒麦角固醇和海藻糖含量高，不同絮颗粒大小的群体乙醇耐性和乙醇产量存在明显差别，这些研究结果为发展燃料乙醇生产中发酵过程的控制策略提供了基础。
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Influence of floc size distribution on the ethanol tolerance of a self-flocculating yeast strain SPSC01
Abstract：Employing the Focused Beam Reflectance Measurement (FBRM) on-line monitoring system, the yeast floc populations with the average sizes around 100, 200, 300, and 400 μm were obtained by adjusting the mechanical stirring rates of the fermentation system, and the ethanol tolerance of these floc populations was studied in a 3-L bioreactor under fed-batch culture. When subjected to 20%(V/V) ethanol shock for 6 h at 30 ℃, the remained viability was measured to be 3.5%、26.7%、48.8% and 37.6% for the aforementioned four floc populations, and the highest ethanol production yield was achieved for the 300 μm flocs, 7.2% higher than that of the 100 μm flocs. The amounts of trehalose and ergosterol (including free ergosterol and total ergosterol) were found to be positively correlated with the average size distributions from 100 to 300 μm; however, in the 400 μm flocs, the content of trehalose and ergosterol decreased, which coincided with its reduced ethanol tolerance comparing to that of the 300 μm flocs. Furthermore, when subjected to 15%(V/V) ethanol shock at 30 ℃, the equilibrium nucleotide concentration and plasma membrane permeability coefficient（P′）of the 300 μm flocs accounted for only 43% and 52% respectively of those of the 100 μm and 200 μm populations, indicating that the effect of floc size distribution on the ethanol tolerance of the self-flocculating yeast strain SPSC01 is closely related to plasma membrane permeability. These results demonstrated that an optimal floc size distribution with the highest ethanol tolerance and ethanol production level can be obtained by controlling mechanical stirring rates of the bioreactor, which provides basis for the process optimization of fuel ethanol production using this self-flocculating strain.
Keywords： Ethanol tolerance Floc size distribution On-line monitoring Self-flocculating yeast.
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絮凝颗粒粒度分布对自絮凝酵母SPSC01乙醇耐受能力的影响
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