Inhibition of biofilm formation and settlement of barnacle larvae by a biosurfactant produced from a marine biofilm-forming Exiguobacterium sp. R58

Abstract

Natural product based antifouling strategies are promising alternatives for achieving biofouling control with minimal environmental burden. Although microbial biosurfactants have shown antimicrobial and antibiofilm activities, their efficacy on settlement of barnacles, among the most problematic of biofouling organisms in the marine environment, has not be evaluated. Biofilm-forming bacteria isolated from the seawater cooling system of a power plant were screened for biosurfactant production and one of the promising strains was identified as Exiguobacterium sp. R58. Production, characterization and anti-biofouling activity of the biosurfactant was determined. Emulsifying activity of 68–89% was achieved at 4−100 °C, 2–12% salinity and 2–12 pH. Biofilm formation by Escherichia coli, Staphylococcus aureus, Salinococcus sp., and Marinobacter sp. was strongly inhibited (80–92%) in the presence of 2000 μg/mL biosurfactant. Cypris larval settlement was impaired by the biosurfactant without causing mortality. Biosurfactant coated surfaces prevented biofilm formation and cypris settlement. Adhesion of bacteria on biosurfactant coated surfaces was 75–93% lower as compared to control. Cypris settlement was inhibited completely in Petri dishes coated with 5.6–22.7 mg/cm2 in no-choice assays and 1.3 mg/cm2 in choice assays. Antibiofouling activity of the biosurfactant was related to surface modification, thus promising for developing non-toxic antifouling materials.