Lactase production by Saccharomyces fragilis IZ 275 using different carbon sources

Abstract This study sought to create a better fermentation medium to maximize lactase production by Saccharomyces fragilis IZ 275 using different carbon sources, including reconstituted powdered cheese whey. A factorial design 24 was applied to evaluate the significant effects of variables which compose the fermentation medium. Then, a steepest descent-ascent design was applied to obtain the maximum activity. A Rotational Central Composite Design (RCCD) 24 was made to optimize the fermentation medium. We verified that the cheese whey, a by-product of the dairy industry, can be employed as an excellent fermentation medium by yeast, within the bioeconomy concept and used by the dairy industry as product with additional value. The employed methodology is an efficient tool in the optimization process for β-galactosidase production. In the optimized fermentation medium, the maximum production of β-galactosidase (54.68 U/mL) by S. fragilis IZ 275 is obtained with 14 g/L sucrose, 17.7 g/L reconstituted powdered cheese whey, 5.14 g/L yeast extract and 8.85 g/L peptone.摘要 本研究旨在构建更优质的发酵培养基，以最大化脆壁酵母（Saccharomyces fragilis）IZ 275的乳糖酶产量，实验采用包括复原干酪乳清在内的多种碳源开展研究。采用2⁴因子析因设计，对构成发酵培养基的各变量的显著影响进行评估；随后采用最速上升-下降设计以获取最高酶活。进一步通过2⁴次旋转中心复合设计（Rotational Central Composite Design, RCCD）对发酵培养基进行优化。本研究证实，契合生物经济（bioeconomy）理念，乳制品工业副产物干酪乳清可作为酵母的优质发酵培养基，同时可被乳制品工业开发为高附加值产品。本研究所采用的方法是β-半乳糖苷酶（β-galactosidase）生产优化过程中的高效工具。在优化后的发酵培养基中，脆壁酵母IZ 275可实现β-半乳糖苷酶的最高产量（54.68 U/mL），此时培养基组分为：蔗糖14 g/L、复原干酪乳清粉17.7 g/L、酵母提取物5.14 g/L、蛋白胨8.85 g/L。