Kolev Petar, Rocha-Mendoza Diana, Ruiz-Ramírez Silvette, Ortega-Anaya Joana, Jiménez-Flores Rafael, García-Cano Israel
Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Ct., Columbus 43210.
JDS Commun. 2021 Nov 25;3(1):1-6. doi: 10.3168/jdsc.2021-0145. eCollection 2022 Jan.
β-Galactosidase is an enzyme produced by some strains of lactic acid bacteria (LAB) commonly found in dairy products; however, industrial demand for these enzymes is still low. Acid whey (AW), a lactose-rich byproduct, has large output from cottage cheese and remains unexploited. The purpose of this study was to understand the production mechanism of β-galactosidase from LAB using AW as a culture medium. First, bioinformatics analysis was conducted on 15 species of LAB. Then, 24 strains were selected and inoculated in de Man, Rogosa, and Sharpe (MRS) broth and in AW medium to compare the bacterial kinetic growth and β-galactosidase production. Bacterial growth and total protein activity were measured using spectrophotometric techniques. β-Galactosidase activity was determined by 2 methods: following the hydrolysis of -nitrophenyl-β-d-galactopyranoside and of 5-bromo-4-chloro-3-indoyl-β-d-galactopyranoside (X-gal) in tryptic soy agar plates. The relative expression of the β-galactosidase gene was performed using real-time quantitative PCR. Despite generally lower growth in AW, 18 strains showed higher β-galactosidase activity when grown in AW compared with MRS medium. The highest β-galactosidase activity in AW was in strain OSU-PECh-4A, which showed almost 5 times higher activity than average. Analysis of 6 selected strains for expression of the 620 gene found higher overexpression in AW than in MRS, regardless of specific β-galactosidase activity. Strains of LAB such as OSU-PECh-4A could valorize AW through the production of β-galactosidase (as an aid to lactose digestion) and production of prebiotic galactooligosaccharides.
β-半乳糖苷酶是由一些常见于乳制品中的乳酸菌（LAB）菌株产生的一种酶；然而，工业对这些酶的需求仍然很低。酸性乳清（AW）是一种富含乳糖的副产品，来自农家干酪的产量很大且尚未得到开发利用。本研究的目的是了解以AW为培养基时LAB产生β-半乳糖苷酶的机制。首先，对15种LAB进行了生物信息学分析。然后，选择24株菌株接种到德、罗、沙氏（MRS）肉汤和AW培养基中，以比较细菌的动力学生长和β-半乳糖苷酶的产生。使用分光光度技术测量细菌生长和总蛋白活性。β-半乳糖苷酶活性通过两种方法测定：在胰蛋白胨大豆琼脂平板中跟踪对硝基苯基-β-D-吡喃半乳糖苷和5-溴-4-氯-3-吲哚基-β-D-吡喃半乳糖苷（X-gal）的水解。使用实时定量PCR进行β-半乳糖苷酶基因的相对表达。尽管在AW中生长通常较低，但与MRS培养基相比，18株菌株在AW中生长时显示出更高的β-半乳糖苷酶活性。AW中最高的β-半乳糖苷酶活性存在于OSU-PECh-4A菌株中，其活性几乎比平均值高5倍。对6株选定菌株进行620基因表达分析发现，无论特定的β-半乳糖苷酶活性如何，在AW中的过表达都高于MRS。诸如OSU-PECh-4A等LAB菌株可以通过产生β-半乳糖苷酶（作为乳糖消化的辅助）和益生元低聚半乳糖来利用AW。
