乳酸克鲁维酵母透性化细胞β-半乳糖苷酶催化合成低聚半乳糖

Preparation of Galacto-oligosaccharides by the β-galactosidase of Kluyveromyces lactis Permeabilized Cells

研究了乙醇对乳酸克鲁维酵母细胞的渗透处理工艺,对所得透性化细胞β-半乳糖苷酶的性质进行了考察,并用于催化乳糖合成低聚半乳糖.结果表明,乙醇体积分数为40%,室温渗透处理1min可得到理想的透性化细胞β-半乳糖苷酶.该透性化细胞酶的最适pH为8.0,最适温度为37℃,Fe2+、Mg2+、Pb2+、Al 3+和Fe3+对其有激活作用,Cu2+和Bi 3+则抑制其酶活.加酶量和乳糖浓度是影响低聚半乳糖合成速率和收率的2个重要因素.确定了透性化细胞β-半乳糖苷酶合成低聚半乳糖的最佳条件为,初始乳糖浓度500g/L,透性化细胞加入量125g/L,反应时间8.5h,此时低聚半乳糖生成量为98.93g/L,收率为19.79%,透性化细胞至少可重复利用2次.

The permeablization Kluyveromyces lactis cells and galacto-oligosaccharldes （GOS） synthesis were investigated in this paper. After treatment at room temperature for 1 rain by using 40% ethanol, the permeability of K. lactis cells was changed, thus allowing the transit of low molecular weight compounds in and out of the cells, β--galactosidase of ethanol- permeabilized K. lactis cells was stable at pH 8.0, 37 ℃ and could be stimulated by some met- al ions, such as Fe2＋, Mg2＋, Pb2＋, Al3＋ and Fe3＋, while inhibited by Cu2＋ and Bi3＋. The per- meabilized K. lactis cells exhibited excellent GOS synthesis activity. The maximum GOS con- centration produced by permeabilized cells reached 98.93 g/L with the yield of 19.79% when initial lactose concentration was 500 g/L with addition of 125 g/L permeabilized cells at 37℃ for 8.5 h, and the permeabilized cells could be reused at least for two times in preparation of GOS.