Production of Polyhydroxybutyrate (PHB) by Bacillus megaterium DSM 32 from Residual Glycerol of the Bioenergy Industry

Biodegradable polymers from renewable resources are generating growing interest in the plastic industry because they have properties similar to synthetic polymers. Polyhydroxyalkanoates, mainly polyhydroxybutyrate (PHB), have mechanical and physicochemical properties very similar to their synthetic counterparts. This work explores the use of residual glycerol from the bioenergy industry for the production of PHB by Bacillus megaterium DSM 32. The glycerol works as a source of carbon and energy. Raw glycerol was purified with sulfuric acid in order to neutralize saponified fatty acids. The purification process generated three different phases. One of the phases was the glycerol-rich layer; this layer was filtered and concentrated by vacuum distillation process. The purity of the glycerol was determined by thermogravimetric analysis (TGA). Additionally, the physicochemical properties, like viscosity, pH, ash content and density, were measured. The experiments were conducted in shake flasks at 30 degrees C and 120 rpm. Different glycerol concentrations (20, 30, 40 g/L) were used to evaluate the influence of the initial concentration of glycerol on the biomass accumulation and biopolymer production. The purified glycerol obtained had a high purity (similar to 89.5-92.13%); this material does not contain fatty acids, although it contains similar to 3.7% salts. The final PHB concentration obtained was 0.054 mg/mL.