Abstract

In this study, poly-beta-hydroxybutyrate (PHB) production by the Bacillus subtilis 25 and Bacillus megaterium 12 strains was investigated in nutrient broth medium at different incubation times (between 6 h and 48h). The best PHB production and all yields of these strains were determined. The productions were 0.101 g/L, 0.142 g/L and the percentage yields were 18.03%, 14.79% after 45h, respectively. At 48th h, there was a decrease in PHB yields. In our study, the effects of different carbon and nitrogen sources on PHB production in these strains were also tested. While the strains produced less PHB in nutrient broth medium with different carbon and nitrogen sources, the highest level of PHB accumulation of the strains was observed in the medium with protease peptone. In this nutrient broth medium with protease peptone the percentage PHB yield of B. subtilis  25 was determined as 78.69%, while in the same nitrogen sources this percentage in B. megaterium 12 was determined to be 77.00%.

Key words: Poly-b-hydroxybutyrate, Bacillus subtilis, B. megaterium , Different carbon and nitrogen sources, incubation time.