A comprehensive review on enhanced production of microbial lipids for high-value applications

Microbes are the major source of lipids, which include fatty acids and glycerolipids. Lipids are used as bioplastic and biosurfactants in several industries. Value-added compounds like alpha-linolenic acid, 1,3-propanediol (1,3-PDO), fatty acid methyl esters (FAME), keto-carotenoids, lactic acid, 2,3-butanediol, citric acid, lutein, polyunsaturated fatty acids (PUFAs), 1,3-dihydroxyacetone, oleic acid, propionic acid, and succinic acid have huge applications in textile, cosmetic, food, metallurgy, and pharmaceutical industries. These microbial-based lipids have various industrial and technology applications as printing inks, lubricants, coatings, polymers, solvents, leather processing, hydraulic fluids, surfactants, glycerin (glycerol), pesticide/herbicide adjuvants, and fuels. Biotechnological processes such as medium engineering and metabolic engineering can enhance lipid production in microbes to a certain limit. Integrated biorefinery concept was introduced for cost reduction, efficient utilisation of feedstocks, high yield, zero waste discharges, high productivity, and economically viable technology development. It integrates the conversion of biomass to energy and other high-value products. This review focuses on the bioreactor design; integrated biorefineries; genetic and metabolic engineering prospect of enhanced microbial lipid production; application of microbial lipids in various sectors such as pharmaceuticals, dietary supplement, cosmetics, and biodiesel production; costing; and life cycle assessment. Furthermore, value-added products such as carotenoids, organic acids, polyhydroxyalkanoates, and fatty acids were also discussed. Graphical abstract: [Figure not available: see fulltext.]