Unlocking the Potential of Natural Deep Eutectic Solvents for the Valorization of Different Biological Materials

Extractions with natural deep eutectic solvents (NADESs) as tunable, biocompatible and green solvents are a new widely applicable platform in cascading fractionation of highly complex biological materials. Roles of NADESs can be multiple, from extraction of phenolics and polysaccharides to stabilization or even support of biocatalysts and extracted compounds in further bioprocessing. Their utilization offers alternative valorization routes in comparison to conventional extractions, decreasing the GHG emissions of underexploited wasted biomass and fossil-based solvents. This study examined the potential of different NADESs as solvents in fractionation of three distinctive biological materials-corn stalks, common nettle, and mycelium of the higher fungus <i>Fomes fomentarius</i>. NADESs were used for delignification and extraction processes, and selected extracts were tested as substrates for lactic acid bacteria (LAB) with an aim to enhance them through microbial biotransformation. For this purpose, D-glucose-glycerol (1:3), betaine-1,3 propanediol (1:4), and betaine-glycerol (1:2) NADESs were selected. According to the results, betaine-glycerol NADES was the most promising solvent for achieving the highest delignification rate and the highest yields of extracted polyphenols and polysaccharides. Moreover, the obtained extracts showed the ability to serve as growth media for LAB, emphasizing the possibility of establishing novel LAB-fortified products, aligning with circular and zero-waste biorefinery principles.