Valorization of waste cooking oil for bioproduction of industrially-relevant metabolites in Ashbya gossypii

Waste cooking oil (WCO) is a byproduct of culinary processes, which undergoes degradation due to high temperatures during frying and cooking. Beyond its detrimental effects on health, including potential carcinogenic effects, WCO poses a significant environmental threat, emphasizing the need for urgent recycling efforts. Valorization of WCO as a carbon source for microbial fermentations emerges as a feasible alternative in a bioeconomy context. The aim of the present work is to explore the ability of Ashbya gossypii, a natural overproducer of riboflavin that is currently used in the industrial production of the vitamin, to exploit WCO for the production of industrially relevant metabolites such as riboflavin, folates, biolipids and monoterpenes. Our results demonstrate that WCO is an effective carbon source for A. gossypii bioproduction of riboflavin, folates and biolipids, reaching among the highest titers described so far in flask fermentation: riboflavin titer (312.5 mg/L) increased 4.8-fold compared to glucose-based medium; folate production reached 7.6 mg/L; and the intracellular lipids were above 80 % of the cell dry weight. In contrast, the production of the monoterpenes limonene and sabinene was not improved with the utilization of WCO. Taken together, our results present a proof-of-principle for the implementation of a novel bioprocess for the valorization of WCO using the industrial fungus A. gossypii.