from all substrates were used an alternative carbon for the PHB production. The presence of nitrogen source where ammonium sulphate was the best source of nitrogen that helps to produce PHB compared the other concentration of the studied concentrations of ammonium sulphate. Regarding incubation time and temperature and pH, optimum PHB production conditions were 48 h, 30°C and 7.0, respectively. C/N ratio was also one of the factors that affected the production of PHB by B. cereus. The ratio of C/N that reaches 20:1 was considered the best ratio to produce the highest production of PHB. Thus by utilizing the optimum culture conditions we can solve the problems of high cost of PHB production.