Utilization of brewery spent grain as an exclusive carbon source for microbial synthesis and characterization of biodegradable polyhydroxybutyrate (PHB) polymer

In the present study Microbial approach is used to synthesis an environmentally friendly Polyhydroxybutyrate (PHB) biopolymer by a utilizing brewery spent grain as an exclusive carbon source. The aim of the study was the production of Poly-hydroxy Butyrate (PHB), a bio-plastic using glucose recovered from spent grain with the aid of bacillus subtilis via bacterial fermentation. The Spent grain was utilized as a carbon source and it was hydrolyzed for PHB synthesis, also, its chemical composition and proximate analysis were determined. After the spent grain was hydrolyzed, the benedict test and UV-spectroscopy were used to determine glucose concentration. Then, the Box-Behnken designs was used to analyze the effects of fermentation duration, pH, and incubation temperature on PHB yield were assessed. According to the experimental findings, the optimum yield of PHB (5.03 ± 0.14 g/l of neat PHB) was attained at a temperature of 37 °C, pH of 7 and fermentation time of 48 hr. The Bacillus subtilis accumulated PHB was characterized by using UV-Vis spectrophotometer, Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) to validate the polymer's structure as PHB. Likewise, biodegradability, water absorption and water solubility test were carried out. The study's findings demonstrated that it is possible to produce PHB using Bacillus subtilis , which is an environmentally friendly polymer using brewery’s residues (spent grain) as an appropriate carbon source to lower the cost of production and ease the material's disposal issue.