Fermentation of organic wastes through oleaginous microorganisms for lipid production - Challenges and opportunities

Organic waste streams are produced in huge quantities globally and their suitable management is urgently needed. These streams can be used as feedstocks for various bioprocesses to produce bio-based food, industrial products, and energy. The conversion of organic wastes into bio-based products (e.g., lipids) and energy contributes to the protection of the environment, food security, and the development of a sustainable bioeconomy. Among various bioprocesses, the fermentation of organic wastes into lipids presents a promising technical process for enhancing the conversion of organic wastes into bio-based products. Lipid production from organic streams by oleaginous microorganisms has attracted attention as it has the potential to partially replace fossilbased fuels and be used in many industries. Oleaginous microorganisms act as factories that can grow on different carbon substrates like agri-food streams, municipal wastes, industrial wastes, etc., thus making them suitable players in the bio-based economy by producing lipids known for having numerous applications. Therefore, this review aims to update knowledge of microbial lipid production from low-cost organic wastes with an emphasis on lipogenesis in oleaginous microorganisms. Various lipid-enhancing strategies particularly through genetic and metabolic engineering, co-cultivation, and laboratory evolution; while factors affecting them are discussed. Recent advancements for developing highly efficient microbial lipid production processes have also been discussed along with the potential application of the produced lipids. Finally, the contribution of microbial lipids to the biobased economy and environment was analysed. The challenges which need to be addressed through concerted research efforts are also highlighted.