From Wastewater Treatment Plants to the Oceans: A Review on Synthetic Chemical Surfactants (SCSs) and Perspectives on Marine-Safe Biosurfactants

Synthetic chemical surfactants (SCSs) are a versatile group of amphiphilic chemical compounds synthesized from fossil fuel precursors which have found use in various industrial applications. Their global usage is estimated to be over 15 million tons annually, which has resulted in unabated environmental damage and potential toxicological effects to humans and other organisms. Current societal challenges to ensure environmental protection and reduce reliance on finite resources have led to an increased demand for sustainable and environmentally friendly alternatives, such as biosurfactants, to replace these toxic pollutants. Biosurfactants are biodegradable, non-toxic, and generally environmentally compatible amphiphilic compounds. Although there is enormous potential for microbial biosurfactants to replace SCSs, the key challenge limiting their commercialization relates to their low yields and substantial cost for production compared to that for the SCSs. In this review, we discuss the release of SCSs, with wastewater treatment plants (WWTPs) as the major point source of their release into the ocean, and we then delve into the consequences of these pollutants on marine organisms and humans. We then explore microbial biosurfactants as a replacement for SCSs, with a focus on rhamnolipids, and end with some perspectives on current and future work for commercializing microbial biosurfactants.