title: Coexpression of bile salt hydrolase gene and catalase gene remarkably improves oxidative stress and bile salt resistance in Lactobacillus casei.
abstract: Lactic acid bacteria (LAB) encounter various types of stress during industrial processes and gastrointestinal transit. Catalase (CAT) and bile salt hydrolase (BSH) can protect bacteria from oxidative stress or damage caused by bile salts by decomposing hydrogen peroxide (H(2)O(2)) or deconjugating the bile salts, respectively. Lactobacillus casei is a valuable probiotic strain and is often deficient in both CAT and BSH. In order to improve the resistance of L. casei to both oxidative and bile salts stress, the catalase gene katA from L. sakei and the bile salt hydrolase gene bsh1 from L. plantarum were coexpressed in L. casei HX01. The enzyme activities of CAT and BSH were 2.41 μmol H(2)O(2)/min/10(8) colony-forming units (CFU) and 2.11 μmol glycine/min/ml in the recombinant L. casei CB, respectively. After incubation with 8 mM H(2)O(2), survival ratio of L. casei CB was 40-fold higher than that of L. casei CK. Treatment of L. casei CB with various concentrations of sodium glycodeoxycholate (GDCA) showed that ~10(5) CFU/ml cells survived after incubation with 0.5% GDCA, whereas almost all the L. casei CK cells were killed when treaded with 0.4% GDCA. These results indicate that the coexpression of CAT and BSH confers high-level resistance to both oxidative and bile salts stress conditions in L. casei HX01.
authors.affiliation: Key Laboratory of Functional Dairy of Ministry of Education of People's Republic of China & Municipal Government of Beijing, College of Food Science & Nutritional Engineering, China Agricultural University, Hai Dian District, Beijing, 100083, China.
authors.forename: Guohong
authors.initials: G
authors.lastname: Wang
authors.forename: Sheng
authors.initials: S
authors.lastname: Yin
authors.forename: Haoran
authors.initials: H
authors.lastname: An
authors.forename: Shangwu
authors.initials: S
authors.lastname: Chen
authors.forename: Yanling
authors.initials: Y
authors.lastname: Hao
mesh_terms: D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D001646:Bile / Q000378:metabolism; D001647:Bile Acids and Salts / Q000378:metabolism*; D001709:Biotechnology; D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007780:Lacticaseibacillus casei / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018384:Oxidative Stress; D019936:Probiotics; D013234:Stem Cells / Q000378:metabolism
chemical_list: D001647:Bile Acids and Salts; D006861:Hydrogen Peroxide; D002374:Catalase; D000581:Amidohydrolases; C023154:choloylglycine hydrolase