Microbial valorization of waste cooking oils for valuable compounds production - a review

Waste cooking oils (WCO) are vegetable oils discarded after food frying and great amounts are produced worldwide. Its management is a challenge, due to the environmental risk of illegally disposal into rivers and landfills. The main approaches for WCO valorization included their incorporation as component of animal feed and biodiesel manufacturing. Yet, the development of new feasible approaches is attractive from an economic and ecological standpoint. Due to their composition in triglycerides, untreated WCO can be used as feedstock for microbial growth (several species are able to use them as carbon source) and production of added-value compounds. In this way, microbial valorization of WCO is a sustainable biotechnological approach to upgrade a waste into a renewable feedstock for bio-based industry, favoring the circular economy concept. The objective of this review is to highlight the potential use of WCO in bioprocesses as an alternative to other physicochemical treatments. Firstly, an introduction to WCO problematic is presented, describing most common applications used currently. Then, an extensive review on the use of WCO by microorganisms is shown, focusing on bacterial and fungi species and its exploitation for bioprocesses development to produce metabolites of industrial interest, such as biopolymers, biosurfactants, lipases and microbial lipids.