基于乳糖水解酶的乳酸乳球菌乳糖代谢多样性研究
首发时间:2019-02-08
摘要:乳酸乳球菌(Lactococcus lactis,L. lactis)作为传统的乳制品发酵剂,其乳糖代谢能力一直备受关注。目前,关于乳酸乳球菌乳糖代谢的研究大多集中在β-半乳糖苷酶(β- galactosidase)活力和Leloir途径上,而关于磷酸-β-半乳糖苷酶(P-β- galactosidase)活力和塔格糖-6-磷酸(tagatose-6-phosphate,T6P)途径的报道较少。因此本文选取10株乳酸乳球菌,对菌株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P-β-半乳糖苷酶的活力以及发酵液中半乳糖积累情况进行了测定。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;两种乳糖水解酶活力的高低确定了各菌株主要依赖的半乳糖代谢途径,其中Leloir途径代谢半乳糖易出现积累,而利用T6P途径代谢半乳糖无积累。将利用T6P途径代谢半乳糖的乳酸乳球菌与嗜热链球菌复配,能显著减弱嗜热链球菌的半乳糖积累。
关键词: 乳酸乳球菌 半乳糖代谢 塔格糖-6-磷酸途径 Leloir途径
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Enzymatic analysis of galactosidases reveals biodiversity in lactose metabolism among Lactococcus lactis
Abstract:Lactococcus lactis (L. lactis) is one of the traditional dairy starter cultures, and its lactose metabolism is crucial. The studies of lactose metabolism in L. lactis mostly focused on β-galactosidase activities and Leloir pathway, while the phosphate-β-galactosidase activities and tagatose-6-phosphate pathway were less reported. The growth, acid production, lactose metabolism, activities of β-galactosidase and phosphate-β-galactosidase of 10 L. lactis were determined in MRS-lactose broth where lactose was the sole carbon source. In order to understand the differences between the two galactose metabolic pathways in each strain, the galactose accumulation in the fermentation broth was determined. The results showed that the lactose metabolism of L. lactis had significant differences, and the activities of the two lactose hydrolases determined the galactose metabolism pathway that each strain depended on. Moreover, T6P pathway metabolizes lactose with very limited galactose accumulation in MRS-lactose, while Leloir pathway metabolizes lactose with much galactose accumulation. Combining L. lactis, which metabolizes galactose through the T6P pathway, with the Streptococcus thermophilus could significantly reduce the galactose accumulation.
Keywords: Lactococcus lactis galactose metabolism tagatose-6-phosphate pathway Leloir pathway
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