Utilization of pomegranate waste-peel as a novel substrate for biodiesel production by Bacillus cereus (MF908505)

Abstract

The continuous rising demands and fluctuations in the prices of fossil fuels warrant the search for an alternative renewable energy source to manage the present energy crisis. Thereby, ongoing research activities are actively engaged in developing an environmentally clean synthesis of biodiesel from agro-waste via an oleaginous bacterium process. A potent oleaginous bacterial strain has been isolated from poultry industry wastewater. On the basis of morphology, biochemical and 16S rRNA sequencing analysis, the strain has been identified as Bacillus cereus (MF 908505), which enables 3.1 g L⁻¹ lipid productivity, and the satisfactory production of 5.1 g L⁻¹ cell dry weight with 36% (w/w) lipid content using pomegranate waste-peel as a substrate. 37 °C temperature, 7% carbon source and 140 rpm agitation speed with a 72 h incubation period are found to be the optimum lipid production conditions. Lipids are then extracted and transesterified under the optimized reaction conditions using 0.2% Ca(OH)₂ as a base catalyst and a 1 : 6 bacterial oil to methanol ratio, at 70 °C for 90 min reaction time, which, under these conditions, enables an 85% fatty acid methyl ester (FAME) yield. The esterified FAMEs were subjected to gas chromatography mass spectrometry (GC-MS) measurements, revealing the presence of benzenesulphonic acid methyl esters and methyl esters, thus, doubtlessly, supporting the formation of biodiesel. The resulting FAMEs were characterized further by means of various tools and the properties of the obtained biodiesel were found to match those of standard biodiesel, i.e. ASTM D6751. These results suggest the potential suitability of Bacillus cereus (MF 908505) lipids for use as an agro-waste substrate in the biodiesel conversion process.