Algicidal Activity of Renewable and Ecofriendly Sophorolipid Biosurfactants

ABSTRACT The algicidal effects of renewable and ecofriendly sophorolipids (SL) were investigated under controlled laboratory conditions, against species of algae commonly encountered and identified in swimming pools. A range of SL concentrations was tested in 10‐day laboratory experiments to assess algicidal performance and to monitor cell growth and evaluate effectiveness in algal control. Results indicated that growth was strongly inhibited at the optimal sophorolipid concentration of 0.025 mg/mL, and algal cell densities significantly declined within 1–4 days after treatment (DAT) as compared to untreated controls. At this concentration, algae were irreversibly damaged with no recovery occurring throughout the experimental period. No significant changes in biomass were noticed at lower SL concentrations. Responses were also measured at 2 DAT in terms of total chlorophyll content. At the minimum SL concentration of 0.025 mg/mL, cultures exhibited increased bleaching with chlorophyll declining over 80% for all tested species. Microscopy analyses also confirmed the sensitivity to sophorolipid treatments. Although responses were species specific, some algae were more easily lysed at high concentrations (1 mg/mL). These preliminary results highlight the potential of sophorolipids as alternative to chemical treatment options, and a novel and effective method in mitigating algal species commonly found in swimming pools.