An eco-friendly approach to biosurfactant production using low-cost wastes

It is of great importance to reduce the production cost of biosurfactants, which have application areas in a wide range of industrial processes with their antimicrobial and anti-biofilm properties. Accordingly, it was aimed to determine the potent low-cost waste for the cost-effective biosurfactant production by environmental origin Bacillus sp. strains. 2% (v/v) of individual bacterial strain was inoculated into 50 mL of Bushnell Haas medium (pH:7.0) containing 8% (v/v) of each low-cost waste, 1% (w/v) yeast extract and 0.1% (v/v) trace element, and incubation period was carried out at 30 °C and 150 rpm for 7 days. Following the extraction of the culture supernatants, maximum biosurfactant yielded 0.139 ± 0.003 with potato wastewater by potent Bacillus subtilis MG847158.1. Hemolytic activity, 7.70 ± 0.35 mm zone diameter for oil displacement, 50.1 ± 0.8 emulsification index, 89.73 ± 0.9% bacterial adhesion, and decreasing of surface tension from 72.80 ± 0.1 mN/m to 23.97 ± 0.05 mN/m were also obtained. The extracted biosurfactant was further purified by silica gel column chromatography and characterized as lipopeptide by TLC, FT-IR, NMR, and SEM. In addition to being quite effective against both Gram-negative and Gram-positive bacteria, the highest antimicrobial and anti-biofilm activities of biosurfactant were against two Gram-negatives: E. coli (18.1 ± 0.8 mm) (MIC 1 mg mL⁻¹, MBC 2 mg mL^-1) and K. pneumoniae (97%) strains. To sum up, it is the first study to emphasize that the produced biosurfactant with low-cost potato wastewater can be used as an alternative to commercial antimicrobial agents.