Enhancing polyhydroxybutyrate production from high cell density fed-batch fermentation of Bacillus megaterium BA-019

Abstract

This study demonstrated the improved polyhydroxybutyrate (PHB) production via high cell density cultivation of Bacillus megaterium BA-019 with balanced initial total sugar concentration and carbon to nitrogen (C/N) weight ratio. In the 10L stirred fermentor operated at 30°C, pH 7.0, 600rpm, and 1.0vvm air, with the initial total sugar concentration of 60g/L and urea at the C/N weight ratio of 10:1, 32.48g/L cell biomass with the corresponding PHB weight content of 26.94% and volumetric productivity of 0.73g/Lh were obtained from batch cultivation. Continuing cultivation by intermittent feeding of the sugarcane molasses along with urea at the C/N weight ratio of 12.5:1 gave much improved biomass and PHB production (90.71g/Lbiomass with 45.84% PHB content and 1.73g/Lh PHB productivity). Similar biomass and PHB yields were obtained in the 90L stirred fermentor when using the impeller tip speed as the scale-up criterion.