Increase of bacteriocin-like activity of Bacillus thuringiensis strain by improving nutriculture medium composition

The development of the nutriculture medium composition and the optimal concentrations of its constituent components to increase the bacteriocin-like activity of the strain Bacillus thuringiensis ssp. Dakota are presented. The study was carried out using a multifactor experiment with further processing of statistical data in order to optimize the basic nutriculture medium and maximize the activity of the target product. Sources of nitrogen (peptone and yeast extract) and carbon (glycerin and glucose) were used as optimization factors. The control growth medium was medium "A", traditionally used for the cultivation of bacteria of the genus Bacillus . The degree of impact of the studied factors on the effective feature was determined using the model of multiple linear regression of the first order, whereby the optimal ratio of the components was calculated on the basis of the quadratic model. The ability of the Bacillus thuringiensis ssp. dakota strain to produce a bacteriocin-like substance (BLIS) was revealed. The dependence of BLIS synthesis on the cultivation medium was established: on the carbohydrate-free medium, the antimicrobial activity of BLIS was 1.5 times lower than that on the medium containing glucose and glycerin. To obtain maximum BLIS activity, the carbohydrate medium was optimized using a multifactor experiment performed by the method of orthogonal Latin rectangles. Mathematical models of linear regression of the first and second order were constructed depending on the concentration of nutrient medium components. The optimal concentration of the components was determined on the basis of a second-order regression model that takes into account the effects of the interaction of factors and the nonlinearity of the process. As a result of optimization of the nutrient medium, the quantitative composition of the components of the culture medium was determined: peptone – 9 g/l; yeast extract – 2.6; glycerol – 5.6 g/l, on which the antimicrobial activity of BLIS increased by 60% compared with the activity on the initial medium. It was shown that the synthesis of BLIS, unlike the synthesis of delta-endotoxin, is not regulated by catabolite repression of carbon.