To find optimal growth condition for acetate supply for PHB production in of acetate supply, a number of cyanobacteria were culture with acetate supply but were varied by the amount of light and nitrogen supply into 4 combination: (i) normal nitrogen supply with light (i.e. normal growth condition); (ii) normal nitrogen supply with dark; (iii) nitrogen deprivation with light; (iv) nitrogen deprivation with dark. The results from table 1 suggested that the condition with the highest PHB accumulation under acetate supply is (iiii) nitrogen deprivation with dark.