Optimization of Cultivation Conditions for the Lactobacillus reuteri LR1 Strain to Improve the Biosynthesis of Bacterioc
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OGICALS TECHNOLOGY
Optimization of Cultivation Conditions for the Lactobacillus reuteri LR1 Strain to Improve the Biosynthesis of Bacteriocin-Like Substances A. V. Begunovaa, I. V. Rozhkovaa, T. I. Shirshovaa, O. A. Glazunovab, and T. V. Fedorovab, * aAll-Russia
Research Institute of Dairy Industry, Moscow, 115093 Russia Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, Moscow, 119071 Russia *e-mail: [email protected]
b
Received September 12, 2019; revised October 4, 2019; accepted October 12, 2019
Abstract—The article presents the results of optimization of the culturing conditions to increase the production of bacteriocin-like compounds (presumably including reuterin) by the Lactobacillus reuteri strain LR1. The strain Escherichia coli ATCC 25922, an opportunistic microorganism, the content of which is standardized in foods by the Food Safety Legislation, was selected as an indicator strain of antimicrobial activity. The nutrient medium for L. reuteri LR1 cultivation was optimized to increase the production of bacteriocin-like compounds, and the parameters of two-stage growth of the producer were established: (1) cultivation on the initial medium for biomass accumulation and (2) growth on a water–glycerol medium to convert glycerol to antimicrobial compounds, presumably reuterin. The first stage was carried out as follows: the L. reuteri LR1 culture (5%) was inoculated into a medium with the following composition: hydrolyzed milk—250 mL/L; yeast extract—10 g/L; peptone—5 g/L; glucose—20 g/L; sodium acetate—5.0 g/L; monosubstituted potassium phosphate—2.0 g/L; magnesium sulfate—0.2 g/L, and manganese sulfate—0.5 g/L, pH 6.4–6.6. The cultivation was carried out for 18 h at (37 ± 1)°С. The second stage included the incubation of the obtained biomass in 200 mM of glycerol-containing aqueous solution, pH 6.6, for 2 h at 37°С. The zone of E. coli inhibition caused by the produced bacteriocin-like compounds was 25 mm. Keywords: bacteriocin-like compounds, Lactobacillus reuteri, antimicrobial activity, reuterin, glycerol bioconversion, optimization of the culturing conditions DOI: 10.1134/S0003683820090033
INTRODUCTION Lactic-acid bacteria, in particular, bacteria of the Lactobacillus genus, play an important role in the gastrointestinal tract ecology; a number of microorganisms have a probiotic effect on the human body and farm animals. It should be noted that, in addition to their general healing effect, the metabolites of lactic acid and probiotic microorganisms in food and feed are highly active agents that inhibit pathogenic microbiota [1]. Numerous LAB species produce an antimicrobial component with a broad spectrum of action, reuterin. This compound is synthesized by some L. reuteri species during anaerobic glycerol fermentation. Reuterin biosynthesis is carried out via the conversion of glycerol to 3-hydroxypropionaldehyde (3-HPA) with the involvement of B12-dependent glycerol dehydratase [2]. The reuterin in the aqueous solution is a Abbreviations: CFU—colony-fo
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