Circular microbial oil production and extraction using oleaginous yeasts, post-consumer bioplastic wastes and green solvents.

The present study outlines the development of a circular bioprocess to produce microbial oil using oleaginous yeast from post-consumer bioplastic wastes followed by its extraction using green solvents. Three oleaginous yeasts strains (Lipomyces starkeyi, Rhodosporidium toruloides, Cryptococcus curvatus) were cultivated on acetic acid, lactic acid, succinic acid, crotonic acid, poly(lactic acid) (PLA) hydrolysate and poly(3-hydroxybutyrate) (PHB) hydrolysate. The oleaginous yeast C. curvatus accumulated lipids at all individual carbon sources, besides 10 g/L crotonic acid. PLA and PHB hydrolysates led to 2.5 g/L and 1.3 g/L microbial oil production in shake flask cultures. Microbial oil production reached 8.5 g/L with 43.6 % intracellular content using C. curvatus in a fed-batch bioreactor fermentation process with PLA hydrolysate as the substrate. Downstream microbial oil extraction was evaluated using conventional (hexane, chloroform/methanol) and green solvents (d-limonene, ethyl acetate, 1,3-Dioxolane). The extraction temperature (25-80 °C) and the application of ultrasound assisted extraction (UAE) had a significant effect on lipid recovery yield with the highest value (93.6 % w/w) obtained with 1,3-Dioxolane at 80 °C and 24 h extraction duration after 15 min UAE. The recycling of ethyl acetate showed lower energy consumption and CO2 emissions than 1,3-Dioxolane. The proposed recycling of post-consumer bioplastic wastes could evolve into a sustainable microbial oil production technology as alternative to vegetable oils.