论文部分内容阅读
【目的】以淀粉为原料的乙醇发酵工艺仍然是当前燃料乙醇的主要生产方式。然而,一些原料中含有的果胶物质不仅降低了乙醇产率,而且会导致醪液粘度增大,从而会进一步影响传质和传热、增加设备负担等。构建能够自主降解果胶质的重组酿酒酵母并应用于燃料乙醇生产是值得探索的领域。【方法】论文将来源于黑曲霉的果胶酯酶基因克隆于α因子信号肽下游并通过酵母α-凝集素C-端蛋白的介导构建了在细胞表面锚定表达果胶酯酶的重组酿酒酵母PE。【结果】重组酵母的果胶酯酶表达水平达到2.6 U/g(菌体湿重),并进一步鉴定了重组果胶酯酶性质。以甘薯粉为原料的同步糖化发酵实验中,重组酵母PE的乙醇浓度和乙醇转化率分别达到95 g/L和88.1%,与出发菌株相比提高了2.2%。更重要的是,表面展示果胶酯酶能够显著降低发酵过程中的发酵液粘度。【结论】通过在工业酿酒酵母表面展示表达果胶酯酶不仅能够提高糖化酶等的作用效果和酿酒酵母的代谢能力,而且能够显著降低乙醇生产过程中发酵液的粘度,将对工业规模乙醇生产在降低设备负担、节约能耗方面具有一定的潜在价值。
【Objective】 The main raw material of ethanol fermentation process is still the main mode of production of fuel ethanol. However, some of the raw materials contained in the pectin not only reduce the ethanol yield, but also lead to increase the viscosity of the mash, which will further affect the mass transfer and heat transfer, increase equipment burden and so on. The construction of recombinant Saccharomyces cerevisiae which can degrade pectin autonomously and apply it to the production of fuel ethanol is worth exploring. 【Method】 The pectin esterase gene from Aspergillus niger was cloned downstream of the alpha-factor signal peptide and mediated by the alpha-lectin C-terminal protein of yeast to construct a recombinant pectate esterase anchored on the cell surface Saccharomyces cerevisiae PE. 【Result】 The results showed that the expression level of pectin esterase in recombinant yeast reached 2.6 U / g (cell wet weight), and the properties of recombinant pectin esterase were further identified. In the simultaneous saccharification and fermentation experiment using sweet potato as raw material, the ethanol concentration and ethanol conversion rate of recombinant yeast PE reached 95 g / L and 88.1%, respectively, which was 2.2% higher than the original strain. More importantly, surface-displaying pectin esterase can significantly reduce the viscosity of fermentation broth during fermentation. 【Conclusion】 The results showed that the expression of pectate esterase on the surface of industrial Saccharomyces cerevisiae could not only improve the effect of saccharifying enzyme and metabolism of Saccharomyces cerevisiae, but also significantly reduce the viscosity of fermentation broth in ethanol production. In reducing the burden on equipment, energy conservation has a certain potential value.