Screening, isolation and characterization of biosurfactant-producing Bacillus tequilensis strain ANSKLAB04 from brackish river water

Abstract

Biosurfactants are amphiphilic compounds produced by micro-organisms that are excreted extracellularly and contain hydrophobic as well as hydrophilic moieties which reduce surface tension. These extracellular membrane vesicles aid in the uptake of organic molecules that are used as a source of energy for growth of micro-organisms. These micro-organisms have the ability to grow and proliferate on the oil-based medium like petro-contaminated soil and water. Oil spills and discharge from industry contaminates the water bodies and surrounding land. Many chemical-based technologies and manual cleaning are involved to reduce water and land pollution. Chemicals used are the surfactants that lead to the generation of toxic by-products. Hence, considerable attention has been given to surface-active molecules of biological origin called biosurfactants, produced by microbial species in and around the contaminated area. The present study focuses on identifying a novel biosurfactant-producing bacterial strain from brackish water. The bacterial consortium was isolated from targeted brackish water site. Each bacterial species was tested for its biosurfactant production ability using various assays. Haemolysis, oil spreading, cetyltrimethyl ammonium bromide agar plate, drop collapse, hydrocarbon overlay agar, hydrocarbon assay and lipase production were a few qualitative methods performed. Further, the most efficient biosurfactant producer was identified by measuring emulsification index, quantifying biosurfactant production and efficient reduction in surface tension. 16S rRNA gene sequencing was performed for phenotypic characterization of the biosurfactant-producing strain, using Sanger dideoxy sequencing method followed by the phylogenetic assessment. The isolate was found to be a novel Bacillus tequilensis strain, named as ANSKLAB04. The novel isolate was deposited in GenBank with Accession number KU529483.