Soil washing potential and characteristics of biosurfactants from bacillus sp. GY19

Abstract

Biosurfactants, produced by various microorganisms, gained several interests during the past decades. This study aims to take a closer look at the biosurfactant production by Bacillus sp. GY19, isolated from planted soil using renewable substrates (molasses, bottom glycerol) and pure glycerol. Molasses and glycerol can be effectively used as substrates for biosurfactant production by this strain, as they reduce surface tensions of culture media up to 31% (29.5 mN/m) and 55% (29.7 mN/m) compared to the control, respectively. Colorimetric tests to quantify the content of lipid, protein and carbohydrates (sulpho-phospho-vanillin-test, Bradford-test and phenol-sulfuric acid test, respectively) revealed the produced biosurfactant as one of lipopeptide type, which could be confirmed by NMR. Bacillus sp. GY19 has been tested for biosurfactant producing genes by Polymerase Chain Reaction and found to contain genes responsible for fengycin, plipastatin and surfactin production. Furthermore, soil washing batch experiments, using three types of soil spiked with crude oil, showed potential of an application of this biosurfactant as a soil washing agent, depending on the type of soil. Solutions containing 2 g/l biosurfactant using 3% pure glycerol as substrate could remove 91% of crude oil from a sandy clay loam soil. Additionally, germination tests with cucumber, tomato and lettuce seeds were conducted with aqueous solutions of the crude biosurfactant extract, showing no inhibition of germination to all tested plants. Furthermore, no microbial inhibition or bactericidal effects could be determined of the biosurfactant solutions, leading to the conclusion that the extracted crude biosurfactant solutions, using molasses and pure glycerol as substrates, are not toxic to the environment. Hence, this study showed potential utilization of lipopeptide from Bacillus sp. GY19 for remediation of crude oil contaminated sites