|Ashby, Richard - Rick|
|FAN, A - Colgate-Palmolive|
|DU-THUMM, L - Colgate-Palmolive|
Submitted to: American Oil Chemists' Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/11/2017
Publication Date: N/A
Technical Abstract: Sophorolipid (SL) is glycolipid biosurfactant produced by yeast. Its general antimicrobial activity was previously reported. In this paper, we present the antimicrobial activity of SL specifically against oral and skin bacteria. Using a microplate to continuously monitor cell growth, we found complete inhibition of cell growth at SL concentrations =1 mg/ml (1,000 ppm) for oral Lactobacilli tested and =50 ug/ml (50 ppm) for the oral uStreptococci. SEM study of SL-treated L. acidophilus (overnight; 1 mg/ml) suffered extensive cell lysis; S. mutans (at SL=130 ug/ml) showed extensive lesions on cell surface but no lysis. SL (at <1 mg/ml; i.e., sublethal dose) is bacteriocidal to the Lactococci, as shown by increased cell-doubling time (Td) and decreased final cell density (by A600nm) in concentration-dependent manner. SL at <50 µg/ml (sublethal dose) is merely bacteriostatic and only incurs cell injury to oral Streptococci, as evidenced by a prolonged lag-time of growth curves in a concentration-dependent manner but no differences in Td and the final A600nm. Standard Minimal Inhibitory Concentration (MIC) test was also performed towards a broad array of oral and skin bacteria. Superior antibacterial properties were achieved against 3 oral Streptococci species tested (MIC < 4ppm). Good antibacterial properties (MIC=19-39 ppm) were also achieved towards some Gram-positive skin bacteria such as S. haemolyticus, C. striatus and pathogenic S. aureus. However, its efficacy towards Gram-negative E. coli is only moderate (MIC=312-625 ppm). In conclusion, the results presented demonstrated the high value of SL as antimicrobials for applications in oral and skin care industries.