Concomitant production of multifunctional metabolites on biodiesel-derived crude glycerol by the oleaginous yeast Rhodotorula babjevae Y-SL7

Yeasts have received significant attention in recent years as major sources of value-added metabolites endowed with various natural biological activities. Among the yeasts studied until now, the so-called red yeasts have a great potential in microbial lipids and carotenoids production serving as precursor for biofuels, oleo-chemicals, and food additives. In this work, biodiesel-derived crude glycerol was used as feedstock for concomitant valuable metabolites production by the oleaginous yeast Rhodotorula babjevae Y-SL7. Under specific conditions, this strain has been shown to accumulate a high intracellular content of microbial oil (> 40%) and to secrete a mixture of polyol esters of fatty acids (PEFA). Using fed-batch fermentation, the appropriate culture conditions were established for maximum lipids and carotenoids production. The characterization of extracted carotenoids reveals the presence of two major compounds, the torularhodin (63.7%) and torulene (36.3%) and their related antimicrobial and antioxidant activities were investigated. Moreover, secreted PEFAs showed therapeutically promising cytotoxic effect against cancer cells and their synergistic action with commercial drug was also established. On the other hand, flow cytometry analysis showed that culture on crude glycerol increases cells membrane permeability and further enhances metabolites recovery. This can facilitate downstream processing and therefore increase the profitability of the production system. Indeed, the present study opens new perspectives for multifunctional metabolites production using cheap industrial by-product through completely eco-friendly processes

Automated summary

Yeasts, especially red yeasts, are attracting significant attention as major sources of value-added metabolites, such as microbial lipids and carotenoids, which have various biological activities and can be used as biofuels, oleo-chemicals, and food additives. This study focuses on using biodiesel-derived crude glycerol as a feedstock for producing valuable metabolites by the oleaginous yeast Rhodotorula babjevae Y-SL7. The study successfully established the optimal conditions for maximum production of lipids and carotenoids. The extracted carotenoids were found to have antimicrobial and antioxidant activities, and the secreted polyol esters of fatty acids (PEFAs) showed cytotoxic effects against cancer cells, with a synergistic action observed when combined with a commercial drug. Additionally, culture on crude glycerol was shown to enhance metabolite recovery through increased cells membrane permeability.