limiting conditions when the strain was screened. This resulted in
the highest values for PHB production (2.72 g/L) and yield (0.20 g/
g). Interestingly, the variation of PHB content for different nitrogen
source was insignificant, in the range of 40–46%, suggesting that
nitrogen source influences more on cell growth rather on PHB content.
From Table 1, generally speaking, organic nitrogen sources are
more favorable to cell growth than inorganic ones, except peptone.
This seems to be inconsistent to the results obtained in some earlier
reports (Pal et al., 2009; Saranya and Shenbagarathai, 2010),
where ammonium nitrate and ammonium sulfate were identified
as the best nitrogen sources, respectively. Interestingly, in the former
work (Pal et al., 2009), tryptone was identified as the least
favorable nitrogen source on PHB yield for Bacillus thuringiensis
IAM 12077. The results in this section suggest that microbial
strains have diverse nitrogen source preference.