马克斯克鲁维酵母对发酵乳中糖代谢的影响

Effect of Kluyveromyces marxianus on Lactose Metabolism in Traditional Fermented Milk

采用高效液相色谱等方法,对乳酸菌单独发酵和向其中添加马克斯克鲁维酵母这两种发酵乳中乳糖代谢主要产物及关键酶活力的变化情况进行对比分析,以确定添加酵母菌对乳糖无氧代谢产生乳酸途径的影响。结果表明:添加酵母菌后乳糖降解速率明显加快(P<0.05),贮藏期间马克斯克鲁维酵母可以对积累的半乳糖进行利用;发酵过程中,由于酵母菌的添加使β-半乳糖苷酶及乳酸脱氢酶活力有显著提高(P<0.05),糖酵解途径关键限速酶——己糖激酶和丙酮酸激酶活力增加(P<0.05);含有酵母菌的发酵乳p H值下降(滴定酸度上升)较乳酸菌单菌发酵快(P<0.05),这与添加酵母菌后发酵乳中乳酸含量显著增加(P<0.05)有关;丙酮酸含量变化不显著(P>0.05)。该研究揭示了马克斯克鲁维酵母的添加对乳糖酵解具有一定促进作用。

In order to ascertain the effect of co-fermentation with Kluyveromyces marxianus on the biosynthesis pathway of lactic acid by anaerobic metabolism of lactose, the contents of main lactose metabolites in fermented milks with lactic acid bacteria alone and in combination with Kluyveromyces marxianus were analyzed and compared by HPLC, accompanied by comparative measurement of related key enzymes activities. The results showed that lactose was degraded at a markedly accelerated rate during co-fermentation with Kluyveromyces marxianus and lactic acid bacteria （P 〈 0.05）. Kluyveromyces marxianus could utilize the produced galactose during subsequent storage. Moreover, the presence of the yeast resulted in significantly enhanced activities of β-galactosidase, lactate dehydrogenase, pyruvate kinase and hexokinase during the fermentation process （P 〈 0.05）. As a result, hexokinase and pyruvate kinase, the key rate-limiting enzymes in the Embden-Meyerhof-Parnas （EMP） pathway, were significantly activated （P 〈 0.05）. pH declined faster （P 〈 0.05） during co-fermentation with Kluyverornyces marxianus than fermentation with single starter culture, which was associated with significantly enhanced production of lactic acid （P 〈 0.05）. However, no significant difference in pyruvic acid content was found between the two fermented milks （P 〉 0.05）. This study reveals that Kluyveromyces marxianus plays an important role in promoting lactose glycolysis.