Food waste recycling to Yarrowia biomass due to combined hydrothermal carbonization and biological treatment

Food waste (FW) to value-added application represents a demanding opportunity in the circular economy. As one of the approaches, FW hydrothermal carbonization (HTC) delivers an aqueous phase (HTC-AP), which would be suitable when applied to microbial growth and lipid production. In this context, this current work explored HTC-AP from FW obtained through hydrothermal carbonization (temperatures 200 to 260˚C) for microbial growth of 14 different Yarrowia species. Among these strains, Y. lipolytica, Y. keelungensis, Y. porcina, and Y. galii showed the ability to utilize HTC-AP. In HTC from 200˚C high optical density (OD600) reaching above 1.2 for the 4 species was observed. An increase in the temperature by 20˚C declined the growth of Y. lipolytica, Y. porcina, and Y. galii by 17%. However, Y. keelungensis showed good growth regardless of the HTC temperature. Further, the lipid produced better at higher biomass 240˚C compared to 260˚C during the HTC. Further, Y. yakushimensis showed the highest growth rate among all the analyzed media (0.12 – for medium 2 (0.45 NH4+ and 200˚C). Although the composition of HTC-AP is very diverse and often toxic, some analyzed yeast species can use the contained compounds as a carbon source for biomass and lipid biosynthesis. The presented possibilities are a very good starting point for developing processes on a larger scale.