OPTIMIZATION OF NUTRIENT MEDIUM COMPOSITION FOR CULTIVATION OF BACILLUS THURINGIENSIS 87/3 ENTOMOPATHOGENS
Keywords:
optimization, cultivation, B. thuringiensis var. thuringiensis, nutrient medium.Abstract
The aim of the research was to develop an optimal liquid medium composition for bacteria strain B. thuringiensis 87/3 which is the most favorable for the identifiying the potential production of biologically active components. Nutrient medium for cultivation of Bt 87/3 was optimized base on a full-fledged experiment, according to the Box-Behnken (33) plan. The influence of different medium composition on the growth of microorganisms was investigated during active experiment process. The nutrient medium for cultivation was optimized by the composition of carbon and nitrogen feed, as well as on the content of micro elements. To increase the yield of heat-resistant spores and the amount of endotoxin, the nutrient medium was enriched with corn extract, amino acids and mineral salts (Mg, Mn, diammonium phosphate). The rational limits and the corresponding optimal values of the substances (factors) that make the nutrient medium are determined. Optimum concentrations were investigated in the medium of carbon source (15 g/l of glucose), nitrogen (10 g/l of corn extract) and content of phosphorus-containing inorganic salts (1,5 g/l of diamonium phosphate). When growing this strain in periodic conditions at 30°C, the number of viable cells reached 4,4×109 cells/ml, while synchronous spore formation was observed. The optimal component variant is at the intersection of the maximum value of the desirability function in the specified interval of each factor. In this case, rational limits and corresponding optimal values factors that make up the B. thuringiensis nutrient medium are determined. Nutrient medium that was optimized can be recommended for cultivation of Bacillus thuringiensis 87/3 in laboratory and production conditions.
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