Optimization of conditions for a surfactant-producing strain and application to petroleum hydrocarbon-contaminated soil bioremediation.

Petroleum hydrocarbon-contaminated sites have been mainly remediated through the surfactant-enhanced soil leaching method. However, the commonly used chemical surfactants have poor biocompatibility and are prone to form residues in fields. Therefore, the purpose of this research is to establish an effective system of biosurfactant remediation in the field and provide instructions for common bioremediation challenges. First, wild-type Bacillus amyloliquefaciens A3, which produced lipopeptide biosurfactant, was used to improve the production of biosurfactant by atmosphere and room temperature plasma (ARTP) mutagenesis. Second, the mutant 1-24 was selected from a total of 174 mutants due to the outstanding yield. Subsequently, 1-24 was applied in the soil column leaching experiments and removed 45.44% of petroleum hydrocarbons by changing the relevant enzyme activities. Biosurfactant addition and 1-24 inoculation effectively activated a portion of the petroleum hydrocarbons in the soil columns, and 1-24 presented potential as a desired candidate for bioremediation. This is the first report of using ARTP mutagenesis to improve the production of biosurfactants. Simultaneously, we first propose a theoretical system in which the yield of biosurfactant was increased using ARTP mutagenesis for strains and applied the mutants in situ soil bioremediation. This research indicated that the theoretical system was useful in soil columns to simulate field remediation conditions, providing practical references for the bioremediation of contaminated soil.