Comparison of different pretreatment processes envisaging the potential use of food waste as microalgae substrate

A significant fraction of the food produced worldwide is currently lost or wasted throughout the supply chain, squandering natural and economic resources. Food waste valorization will be an important necessity in the coming years. This work investigates the ability of food waste to serve as a viable nutritional substrate for the heterotrophic growth of Chlorella vulgaris. The impact of different pretreatments on the elemental composition and microbial contamination of seven retail food waste mixtures was evaluated. Among the pretreatment methods applied to the food waste formulations, autoclaving was able to eliminate all microbial contamination and increase the availability of reducing sugars by 30%. Ohmic heating was also able to eliminate most of the contaminations in the food wastes in shorter time periods than autoclave. However, it has reduced the availability of reducing sugars, making it less preferable for microalgae heterotrophic cultivation. The direct utilization of food waste containing essential nutrients from fruits, vegetables, dairy and bakery products, and meat on the heterotrophic growth of microalgae allowed a biomass concentration of 2.2 × 108 cells·mL?1, being the culture able to consume more than 42% of the reducing sugars present in the substrate, thus demonstrating the economic and environmental potential of these wastes. ; This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of the UIDB/04469/2020 unit, with DOI 10.54499/UIDB/04469/2020, and by LABBELS—Associate Laboratory in Biotechnology, Bioengineering and Micro-electromechanical Systems, LA/P/0029/2020. This work was funded by the European Union throughthe Horizon 2020 research and innovation program under Grant Agreement No 101036388. Pedro Geada acknowledges FCT for the Junior Research contract obtained under the scope of the Scientific Stimulus Employment with the reference 2022.00930.CEECIND (https://doi.org/10.54499/2022.00930.CEECIND/CP1718/CT0023). ...