Optimisation of Polyhydroxy Butyrate Production by Lysinibacillus fusiformis and Metabacillus indicus isolated from Spent Engine-oil Contaminated Soil

Abstract

This study isolated bacteria from spent engine oil-contaminated soil and optimized their production of polyhydroxybutyrate (PHB), a biodegradable polymer belonging to the polyesters classes that are of interest as bioderived and biodegradable plastics. Out of 12 bacterial isolates (species of Bacillus, Pseudomonas, Staphylococcus and Lactobacillus) recovered from the spent engine oil contaminated soils, and screened for their capacity to accumulate polyhydroxybutyrate (PHB), only two bacterial isolates (Lysinibacillus fusiformis and Metabacillus indicus), showed significant PHB production. L. fusiformis produced PHB at a concentration of 1.5 g/L, while M. indicus produced PHB at a concentration of 1.0 g/L. Optimal production conditions included a temperature of 35°C, agitation speed of 100 rpm, neutral pH of 7.0, glucose as the carbon source, and peptone as the nitrogen source. Gas chromatography-mass spectrometry confirmed the presence of PHB in the extracted samples, with hexadecanoic acid methyl ester identified as the predominant peak. These findings highlight the potential of bacteria from engine oil-contaminated soil as efficient PHB producers and contribute to the development of sustainable and biodegradable plastics.