Production of biosurfactant by lactic acid bacteria using whey as growth medium

The aim of this study was to produce biosurfactants from whey waste using Streptococcus thermophilus, Lactobacillus acidophilus, and Lactobacillus rhamnosus as well as to determine oil spreading, emulsification index, surface tension, and antiadhesive properties in these biosurfactants. Additionally, the capability of biosurfactant production from whey waste in the dairy industry was compared with that of MRS broth, a commercial culture medium. The presence of biosurfactants by all lactic acid bacteria was detected using the oil spreading test. Zone diameter due to the surface activity of lactic acid bacteria strains ranged from 1.87 to 5.92 cm. Biosurfactants from both whey medium and MRS broth reduced surface tension. Differences between data from whey medium and MRS broth were statistically insignificant in terms of the biomass, oil spreading, and surface tension of biosurfactants. Emulsification index values recorded after 1 h, 24 h, and 1 week were significantly different and ranged from 19.50% to 58.00%. The highest emulsification activity was exhibited by L. acidophilus from whey medium in the first hours. A 10 mg/mL concentration of biosurfactants was able to prevent S. aureus, P. aeruginosa, and E. coli adhesion 37.25%-52.5%, 10.25%-23.25%, and 5.32%-11.50%, respectively. E. coli was more resistant to the biosurfactants than the other pathogens were. On the other hand, biosurfactants from L. rhamnosus had the lowest antiadhesive effects. In general, biosurfactants from whey medium and MRS broth were similar in terms of antiadhesion properties. The present study showed that dairy wastes could be an appropriate medium for cost-effective biosurfactant production by lactic acid bacteria for the benefit of the food, pharmaceutical, and cosmetic industries.