Fermentation culture technique of cyanobacteria algae-lysing bacteria CZBC1 optimized by response surface method

ObjectiveThe fermentation cultivation technique of cyanobacteria algae-lysing bacteria—Bacillus cereus CZBC1 were optimized in order to provide technical support for the industrial fermentation production of algae-lysing bacteria agent.MethodBased on single-factor experiment,the optimal carbon source and nitrogen source for the growth of B. cereus CZBC1 were screened. Then,on this basis,the optimal value of key factors was determined by using central composite design(CCD). Regression analysis was conducted by Desig-Expert 8.0.5,and the optimum fermentation culti-vation parameters of CZBC1 were obtained by response surface analysis.ResultThe results showed that the best carbon source and nitrogen source for B. cereus CZBC1 were bran+molasses(1:1)and yeast extract respectively. Amount of bran+molasses(A),amount of yeast extract(B),pH(C)and culture time(D)were set as factor variables,and sporeNumber of strain CZBC1(lgN)as response value,based on which the quadratic multiple regression equation was fitted as follows: lgN=8.5019-0.2222A+0.0998B-0.1292C+0.3801D+0.2194AB-0.1133AC+0.1350AD+0.2049BC-0.06513BD+0.06380CD-0.1260A2-0.3152B2-0.0380C2-0.2533D2. Among them,interaction between amounts of carbon source(bran+molasses)and nitrogen source(yeast extract),interaction between carbon source and pH,interaction between carbon source and culture time,and interaction between nitrogen source and pH had extremely significant effects on CZBC1 spore number(P<0.01,the same below). The optimum fermentation culture parameters obtained by response surface analysis for B. cereus CZBC1 were as follows:bran+molasses 6.84 g/L(mL/L),yeast extract 3.36 g/L,pH 6.50,and 42 h culture time. Under such conditions,the actual spore number of CZBC1 was 5.75×108 CFU/mL,which had no significant difference with the theoretical value(5.90×108 CFU/mL)(P>0.05),but it was significantly higher than the spore number cultured by nutrient broth before optimization(1.28 × 107 CFU/mL).ConclusionThe optimum fermentation culture technique for B. cereus CZBC1 optimized by response surface method can effectively improve the spore number. The model established shows sound fitting effects,and can be applied to guide the industrial fermentation production of cyano-bacteria algae-lysing bacteria agent.