Co-production of lipases and biosurfactants by Bacillus methylotrophicus in solid-state fermentation

The production of biosurfactants and lipases through solid-state fermentation (SSF) processes remains relatively unexplored, especially in bacterial applications. The use of solid matrices, eliminating the need for precipitation and recovery processes, holds significant potential for facilitating bioremediation. This study aimed to simultaneously produce biocompounds via SSF using Bacillus methylotrophicus and employ the fermented substrate for remediating soil contaminated with 20% biodiesel. Initial efforts focused on determining optimal conditions for concurrent lipase and biosurfactant production during an 8-day fermentation period. The selected conditions, including a substrate mix of wheat bran and corn cob (80/20), 75% moisture, 1% glycerol inducer, 2% nitrogen, and 1% sugarcane molasses, resulted in a 24.61% reduction in surface tension and lipase activity of 3.54 ± 1.20 U. Subsequently, a 90-day bioremediation of clayey soil contaminated with biodiesel showcased notable biodegradation, reaching 72.08 ± 0.36% within the initial 60 days. The incorporation of biocompounds, biostimulation, and bioaugmentation (Test E2) contributed to this efficacy. The use of the fermented substrate as a biostimulant and bioaugmentation agent facilitated in situ biocompound production in the soil, leading to a 23.97% reduction in surface tension and lipase production of 1.52 ± 0.19 U.