Enzymatic Hydrolysate of Cinnamon Waste Material as Feedstock for the Microbial Production of Carotenoids

In the context of the global need to move towards circular economies, microbial cell factories can be employed thanks to their ability to use side-stream biomasses from the agro-industrial sector to obtain additional products. The valorization of residues allows for better and complete use of natural resources and, at the same time, for the avoidance of waste management to address our needs. In this work, we focused our attention on the microbial valorization of cinnamon waste material after polyphenol extraction (C-PEW) ( Cinnamomum verum J.Presl), generally discarded without any additional processing. The sugars embedded in C-PEW were released by enzymatic hydrolysis, more compatible than acid hydrolysis with the subsequent microbial cultivation. We demonstrated that the yeast Rhodosporidium toruloides was able to grow and produce up to 2.00 (±0.23) mg/L of carotenoids in the resulting hydrolysate as a sole carbon and nitrogen source despite the presence of antimicrobial compounds typical of cinnamon. To further extend the potential of our finding, we tested other fungal cell factories for growth on the same media. Overall, these results are opening the possibility to develop separate hydrolysis and fermentation (SHF) bioprocesses based on C-PEW and microbial biotransformation to obtain high-value molecules.