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Liu Li,Zhe Zheng,Xiao Zhao,Fengyu Wu,Jian Zhang,Zhen-Nai Yang 한국식품과학회 2019 Food Science and Biotechnology Vol.28 No.4
Bacillus methanolicus LB-1 isolated from traditionalrice wine was found to produce a milk clottingenzyme (MCE), and its fermentation conditions wereoptimized using response surface methodology. Then theMCE was produced by ethanol precipitation, and furtherchromatography separation resulted in a 10.46-fold purificationwith a 59.28% recovery. The MCA (milk clottingactivity) of the purified MCE reached 597,310 ± 0.13 SU/g. The optimal temperature of the MCE was determined tobe 50 C and it was stable in the low temperature range of40–45 C. The MCE had an optimum pH of 6.5, and it wasstable under neutral conditions. Calcium chloride at theconcentration of 25 mM was found to be the most effectivestimulus. The MCE was identified by LC–MS to be aputative protein (ID I3EB99) containing 759 amino acidswith a molecular weight of 80.37 kDa and a pI of 9.23.
( Jian Zhang ),( Xue Zhang ),( Li Zhang ),( Yu Juan Zhao ),( Chun Hua Niu ),( Zhen Nai Yang ),( Sheng Yu Li ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.2
Total 121 lactic acid bacteria were isolated from homemade Inner Mongolia extra hard Hurood cheese. Seven of these strains, identified as Lactobacillus plantarum, were studied for probiotic characteristics. All seven strains survived at pH 3.0 for 3 h, or in the presence of oxgall at 0.3% or 0.6% for 4 h, but their viabilities were affected to different extents at pH 2.0 for 3 h. Strains C37 and C51 showed better adherence to Caco-2 cells, and higher hydrophobicity. The seven L. plantarum strains were different in in vitro free radical scavenging activities and cholesterolreducing ability. In vivo evaluation of the influence of L. plantarum C37 on the intestinal flora in a mouse model showed strain C37 could increase the viable counts of lactobacilli in feces of mice and decrease the viable counts of enterococci. When L. plantarum C37 was used to prepare probiotic Hurood cheese, it was able to maintain high viable counts (>7.8 log CFU/g) during the whole storage period, but the composition of the cheese was not changed. These results indicate that L. plantarum C37 could be considered as a promising probiotic strain.
( Xiao Zhao ),( Ya-juan Cui ),( Sha-sha Bai ),( Zhi-jie Yang ),( Miao-cai ),( Sarah Megrous ),( Tariq Aziz ),( Abid Sarwar ),( Dong Li ),( Zhen-nai Yang ) 한국미생물 · 생명공학회 2021 Journal of microbiology and biotechnology Vol.31 No.8
Casein-derived antioxidant peptides by using microbial proteases have gained increasing attention. Combination of two microbial proteases, Protin SD-NY10 and Protease A “Amano” 2SD, was employed to hydrolyze casein to obtain potential antioxidant peptides that were identified by LC-MS/MS, chemically synthesized and characterized in a oxidatively damaged HepG2 cell model. Four peptides, YQLD, FSDIPNPIGSEN, FSDIPNPIGSE, YFYP were found to possess high 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability. Evaluation with HepG2 cells showed that the 4 peptides at low concentrations (< 1.0 mg/ml) protected the cells against oxidative damage. The 4 peptides exhibited different levels of antioxidant activity by stimulating mRNA and protein expression of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), as well as nuclear factor erythroid-2-related factor 2 (Nrf2), but decreasing the mRNA expression of Kelch-like ECH-associated protein 1 (Keap1). Furthermore, these peptides decreased production of reactive oxygen species (ROS) and malondialdehyde (MDA), but increased glutathione (GSH) production in HepG2 cells. Therefore, the 4 casein-derived peptides obtained by using microbial proteases exhibited different antioxidant activity by activating the Keap1-Nrf2 signaling pathway, and they could serve as potential antioxidant agents in functional foods or pharmaceutic preparation.
Cold-Stress Response of Probiotic Lactobacillus plantarum K25 by iTRAQ Proteomic Analysis
Shaoli Liu,Yimiao Ma,Yi Zheng,Wen Zhao,Xiao Zhao,Tianqi Luo,Jian Zhang,Zhen-Nai Yang 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.2
To understand the molecular mechanism involved in the survivability of cold-tolerant lactic acid bacteria was of great significance in food processing, since these bacteria play a key role in a variety of low-temperature fermented foods. In this study, the cold-stress response of probiotic Lactobacillus plantarum K25 isolated from Tibetan kefir grains was analyzed by iTRAQ proteomic method. By comparing differentially expressed (DE) protein profiles of the strain incubated at 10oC and 37oC, 506 DE proteins were identified. The DE proteins involved in carbohydrate, amino acid and fatty acid biosynthesis and metabolism were significantly down-regulated, leading to a specific energy conservation survival mode. The DE proteins related to DNA repair, transcription and translation were up-regulated, implicating change of gene expression and more protein biosynthesis needed in response to cold stress. In addition, two-component system, quorum sensing and ABC (ATP-binding cassette) transporters also participated in cell cold-adaptation process. These findings provide novel insight into the cold-resistance mechanism in L. plantarum with potential application in low temperature fermented or preserved foods.
( Wen Zhao ),( Jian Zhang ),( Yun-yun Jiang ),( Xiao Zhao ),( Xiao-na Hao ),( Liu Li ),( Zhen-nai Yang ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.8
The exopolysaccharide (EPS) produced by Bacillus amyloliquefaciens GSBa-1 was isolated and purified by ethanol precipitation, and DEAE-cellulose and Sepharose CL-6B chromatographies. The molecular mass of the purified EPS was determined to be 54 kDa. Monosaccharide analysis showed that the EPS was composed of predominantly glucose, and it was further confirmed by NMR spectroscopy to be α-glucan that consisted of a trisaccharide repeating unit with possible presence of two α-(1→3) and one α-(1→6) glucosidic linkages. Microstructural analysis showed that the EPS appeared as ellipsoid or globose with a smooth surface. The EPS had a degradation temperature at 240℃. Furthermore, the EPS had strong DPPH and hydroxyl radical scavenging activities, and moderate superoxidant anion scavenging and metal ion-chelating activities. This is the first characterization of a glucan produced by B. amyloliquefaciens with strong antioxidant activity. The results of this study suggest the potential of the EPS from B. amyloliquefaciens GSBa-1 to serve as a natural antioxidant for application in functional products.