β-Galactosidase was produced by the yeast Kluyveromyces lactis NRRL Y1564 in cheese whey supplemented with yeast extract under the optimal temperature of 30 °C, delivering an enzymatic activity of 4418.37 U/gcell after 12 h of process. In order to develop more stable biocatalysts, the enzyme produced by fermentation was immobilized on 2.0% w/v chitosan activated with glutaraldehyde, epichlorohydrin or glycidol, producing a highly active and stable biocatalyst capable of hydrolyzing lactose and producing lactulose simultaneously. The biocatalyst obtained by immobilization in chitosan-glutaraldehyde showed high storage stabilities (100% of its activity when stored at 4 °C 105 days). Regarding the milk lactose hydrolysis by both the soluble and the immobilized enzyme, the conversions obtained were 38.0% and 42.8%, respectively. In this study, by using a biocatalyst deriving from enzyme immobilization to chitosan support, a lactulose production of 17.32 g/L was also possible.

中文翻译：

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乳酸克鲁维酵母NRRL Y1564的β-半乳糖苷酶催化干酪乳清的同时水解和乳果糖的生产。

β-半乳糖苷酶是由乳酸克鲁维酵母NRRL Y1564在添加了酵母提取物的干酪乳清中在30°C的最佳温度下产生的，经过12小时的加工后，其酶活性为4418.37 U / g细胞。为了开发更稳定的生物催化剂，将发酵产生的酶固定在2.0％w / v的戊二醛，环氧氯丙烷或缩水甘油活化的壳聚糖上，从而生产出一种高活性且稳定的生物催化剂，能够同时水解乳糖和生产乳果糖。通过固定在壳聚糖-戊二醛中获得的生物催化剂显示出高存储稳定性（在4°C下存储105天时其活性的100％）。关于通过可溶性和固定化酶两者水解乳乳糖，获得的转化率分别为38.0％和42.8％。在这个研究中，