探究了磷酸-β-半乳糖苷酶和β-半乳糖苷酶对乳酸乳球菌乳糖代谢的影响。通过对12株乳酸菌在以乳糖为单一碳源环境下的生长、产酸、乳糖代谢情况、β-半乳糖苷酶和磷酸-β-半乳糖苷酶活力及发酵液中残留半乳糖含量进行测定,了解不同菌株乳糖代谢的差异。结果表明,不同的乳酸乳球菌乳糖代谢能力存在显著性差异;β-半乳糖苷酶活力较高的菌株发酵液中半乳糖含量为270~4 110 mg/L,而磷酸-β-半乳糖苷酶活力较高的菌株发酵液中半乳糖含量为40~900 mg/L;将磷酸-β-半乳糖苷酶活力较高的乳酸乳球菌与嗜热链球菌复配,发酵液中半乳糖含量较嗜热链球菌单菌发酵时显著降低。磷酸-β-半乳糖苷酶活力较高的乳酸乳球菌有助于降低发酵乳制品中的半乳糖含量。
The effects of phosphate-β-galactosidase and β-galactosidase on lactose metabolism in Lactococcus lactis (L. lactis) were investigated. The growth, acid production, lactose metabolism, activities of β-galactosidase and phosphate-β-galactosidase of 12 strains were determined in MRS-lactose broth where lactose was the sole carbon source. In order to understand the differences between these two galactosidases, the galactose accumulation in the fermentation broth was determined. The results showed that the lactose metabolism of L. lactis had significant differences. Moreover, the galactose contents in the fermentation broth of strains with high β-galactosidase activities ranged from 270 mg/L to 4110 mg/L, while the galactose contents of strains with high phosphate-β-galactosidase activities were in the range of 40 mg/L to 900 mg/L. Combining L. lactis, which had high phosphate-β-galactosidase activities, with Streptococcus thermophilus could reduce the content of galactose. The experimental results showed that L. lactis with high phosphate-β-galactosidase activities contributed to the reduction of the galactose content in fermented dairy products.
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