Optimization of Conditions for Lactobacillus reuteri LR1 Strain Cultivation to Improve the Biosynthesis of Bacteriocin-Like Substances

Abstract

The article presents the results of the study on optimization of culturing conditions to increase the production of a bacteriocin-like compounds, (presumably including reuterin) by the Lactobacillus reuteri LR1 strain. A 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 of the antimicrobial activity. The nutrient medium for the L. reuteri LR1 cultivation was optimized to increase the production of bacteriocin-like compounds, and parameters of the producer phased growing were established: (1), the cultivation on the initial medium for biomass accumulation; and (2), the growth on a water-glycerol medium to converse glycerol to antimicrobial compounds, presumably reuterin. The first stage was carried out as follows: the L. reuteri LR1 strain culture (5%) was inoculated into a medium of 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 process was carried out for 18 h at (37±1) °C. The second stage included the cultivation of the obtained biomass in a 200 mM glycerol-containing aqueous solution, pH 6.6, for 2 h at 37 °C. The inhibition zone of the test E. coli strain caused by the produced bacteriocin-like compounds was 25 mm. bacteriocin-like compounds, Lactobacillus reuteri, antimicrobial activity, reuterin, glycerol byconversion, optimization of culturing conditions This study was partially supported by the Russian Science Foundation (Project no. 16-16-00094).