Breeding Of Natamycin Producing Strain And The Research Of Extracellular Regulated

With the improvement of people’s awareness of food safety, people pay more attention to the use of food preservatives. Natamycin, which is a secondary metabolites produced by Streptomyces fermentation, is an efficient, broad-spectrum and safe 26 carbon-ring antifungal antibiotic and as a new type of biological preservatives widely used in food and medicine field. Natural biological preservative natamycin satisfied market demand gradually become larger, but the natamycin fermentation level is relatively low, resulting in the cost is too high. The domestic and foreign research on improving the yield of natamycin is mostly focused on the breeding and fermentation process optimization, but it didn’t solve the market supply situation. Therefore, in order to improve the yield of natamycin has important significance to explore some new methods and approaches. In this paper, the composite mutagenesis and screening a strain of natamycin producing strain, and regulation of extracellular of Streptomyces natalensis.The atcc37448 of Streptomyces natalensis as the starting strain, by compound mutation with UV and microwave. Through the experiment to determine the optimal mutagenesis parameters: UV lamp power 30 W, the best distance is 25 cm, the best time is 120s; the optimal conditions for the microwave mutagenesis: maximum output power 800 W, rated frequency 2450 MHz, processing time 50 s. Under these conditions, selected a high-yield strain M-65, the fermentation yield of natamycin reached 1.647g/L, compared with the starting strain was increased by 28.56%.Study of sodium acetate, sodium propionate, sodium butyrate, ethanol, n-propanol and n-butanol of different precursors on natamycin yield were added to the culture medium of Streptomyces natalensis, found that these precursors can effectively improve the yield of natamycin, the effect of sodium propionate and sodium acetate is better, so the best precursor of natamycin was sodium propionate and sodium acetate. By optimizing the adding process, determine the optimum adding amount of sodium propionate and acetate were 0.6%, the best add time is 24h; the optimum ratio of sodium acetate and sodium propionate mixed addition was 7:1, the yield of natamycin reached 3.174g/L, increased by 92.71% compared with the control group.By comparing screening cell elicitor and metabolites elicitor of Aspergillus niger, Penicillium chrysogenum, Aspergillus oryzae and Saccharomyces cerevisiae. Results displayed the metabolites elicitor from Penicillium chrysogenum had the strongest acceleration and the production of natamycin reached to 2.871g/L, which was 74.32% higher than that of original production. The optimum inducing conditions were acquired by optimization experiments and the optimal incubation time of the elicitor from Penicillium chrysogenum was 2d. Streptomyces natalensis was grown for 24 h in which fungal elicitor was added into the medium and incubated to 120 h, the yield of natamycin was 3.316g/L, which was increased 101.34% comparing with the control group.