New horizons in the enzymatic production of biodiesel using neoteric solvents

• Biocatalytic production of biodiesel benefits from the emergence of neoteric solvents.
• Current research trends are focused on ionic liquids, deep eutectic solvents and supercritical fluids.
• Enzyme performance in these solvents is the bottleneck in the implementation of these biocatalytic processes.
• Most studies are focused on the use of Candida antarctica lipase B, imidazolium-based ionic liquids, sc-CO2 and edible oils.

Globally, tougher legislation in greenhouse gases emissions is prompting the hunt for more sustainable and competitive strategies to synthesize biodiesel. Although enzyme-catalyzed processes are considered as a more environmentally-friendly option, there are still challenges to be approached like the replacement of traditional solvents due to their well-known disadvantages such as their volatility, toxicity or carcinogenic character. Thus, the emergence of neoteric solvents such as perfluorocarbons, liquid polymers, ionic liquids, deep eutectic solvents or supercritical fluids has opened up new opportunities to reach truly green processes. Nonetheless, literature analysis reveals the scarcity of research works, which are exclusively restricted to the last three types of solvents. One of the critical points to take into account refers to the performance of enzymes in this kind of milieu, as this environment may be deleterious in terms of protein structure, leading to enzyme deactivation. Therefore, the final purpose of this review paper is to identify the current trends of research in the field of neoteric solvents applied to enzyme-catalyzed synthesis of biodiesel and to shed light on the possible existing gaps.