This may be due to the absence of nitrogen stress condition required for accumulation of PHB. The effectiveness of ammonium sulphate 1g/L in enhancing PHB production is in accordance with Khanna and Srivastav, (2005) and Shaaban et al., (2012) who found that this level produced the highest PHB by R. eutropha and Stenotrophomonas species and Pseudomonas species, respectively .