Enhanced biosurfactant production by Bacillus licheniformis stk 01 for hydrocarbons targeted for bioremediation

Abstract

Environmental remediation of organic and inorganic contaminants such as hydrocarbons has been a research focus area of interest. Chemical surfactants have been extensively used for the remediation of contaminated sites for immobilisation of hydrocarbons from environmental matrices. The focus has been on the impact of chemical surfactants on the environment. These petroleum-based chemical surfactants have raised serious environmental concerns as: 1) they are toxic, 2) they deteriorate the environment owing to their non-biodegradability, 3) they are costly, and 4) most are not intended for environmental applications. As such, alternatives had to be found to mitigate concerns associated with the application of such synthetic surfactants in bioremediation. Biosurfactants produced by microorganisms are a potential alternative to these synthetic surfactants. They have minimal environmental impact, are biodegradable and can withstand extreme conditions. However, biosurfactants are associated with high production costs and low production yield. Currently, large-scale production of biosurfactants cannot be achieved. Most research focuses on improving production yield which will contribute to the reduction in production costs. A lichenysin lipopeptide biosurfactant producing Bacillus sp., which grew exclusively on Beta vulgaris agrowaste, was identified. The microorganism was found to be an effective emulsifier for high molecular weight hydrocarbons such as, lubricant oil and diesel. The aim of this study was to improve biosurfactant production yield from this Bacillus sp., including emulsification efficacy by optimising fermentation conditions by supplementing the broth with biocompatible nanoparticles synthesised using a green chemistry approach with B. vulgaris (B. vulgaris) extracts. This study also aimed at reducing production costs by using B. vulgaris agrowaste exclusively as the production medium, both for the biosurfactant and the nanoparticles.