Research Progress on Biosynthesis and Regulation of Conjugated Linoleic Acid in Lactic Acid Bacteria

Conjugated linoleic acid (CLA) has gained considerable attention and has been extensively studied owing to its physiological functions, including weight loss, immune regulation, and anti-carcinogenesis. However, the CLA content is very low in natural sources and insufficient to exert a probiotic effect. Additionally, its chemical synthesis is limited by the lack of isomer selectivity, harsh reaction conditions, and the introduction of organic solvents. Therefore, the synthesis of CLA by microorganisms, especially lactic acid bacteria, holds great promise because of its isomer selectivity, green process, and probiotic effects of lactic acid bacteria. This article reviews the CLA biosynthesis abilities and mechanisms of CLA producers, particularly lactic acid bacteria. In addition, the factors that impact the CLA yield are discussed. Special attention has been paid to the regulation of CLA synthesis, including the optimization of culture media and conditions, co-culturing of different strains, and regulation of the activity and expression of CLA-related enzymes. Furthermore, prospective future research directions for CLA biosynthesis regulation are discussed.