Antibacterial Activity of Sophorolipids Produced by Candida bombicola Gram-positive and Gram-negative Bacteria Isolated from Salted Hides

Abstract

Salted hides and soaked hides treated with certain antibacterialagents, may still contain different proteolytic and lipolyticGram-positive and Gram-negative bacteria that affect the qualityof leather adversely. The prevalence of bacteria resistant toantimicrobial agents in the leather industry has drawn attentionof scientists to search new and effective antimicrobial agents.Examination of antimicrobial glycolipids such as sophorolipidsfor their effectiveness against proteolytic and lipolytic hidedegradingmicroorganisms, may offer important information.Hence, we describe a research that evaluates the susceptibility ofvarious hide-degrading bacteria to sophorolipids. Theseextracellular glycolipids were produced by fermentation usingCandida bombicola ATCC 22214. Palmitic acid, stearic acid, andoleic acid were used respectively to produce SL-p, SL-s, and SL-o.The minimal inhibitory concentrations (MICs) of SL-p, SL-s, andSL-o against Gram-positive endospore-forming bacteria (Bacilluslicheniformis, B. pumilus and B. mycoides), Gram-positive bacteria(Enterococcus faecium, Aerococcus viridans, Staphylococcusxylosus, S. cohnii and S. equorum), Gram-negative bacteria(Pseudomonas luteola, Enterobacter cloacae, E. sakazakii andVibrio fluvialis), and mixed culture of these isolates were examinedusing an agar dilution method. The MICs of both SL-p and SL-oagainst the test bacteria were determined as 19.5 ?g/mL, with anexception that E. cloacae was inhibited by SL-o at a MIC of 9.76?g/mL. Although MICs of SL-p did not change against the testbacteria, the MICs of SL-s (ranging from 4.88 ?g/mL to 19.5 ?g/mL) changed according to species of the test bacteria. The lowestMICs of SL-s were found to be 4.88 ?g/mL against B.licheniformis, B. pumilus, P. luteola, S. xylosus and B. mycoides.The MICs of SL-p, SL-s, and SL-o against the mixed bacterialculture were detected as the same (19.5 ?g/mL). In conclusion,SL-p, SL-s, and SL-o inhibited the growth of 12 different hidebacteria and their mixed culture, and have broad-spectrumactivity. The results obtained in the present study may bevaluable for the development of SL-p, SL-s, and SL-o asantimicrobial surfactants in the preservation and soakingprocesses of hides and skins.