Fungal Enzyme-mediated Organic Acid Production and its Applications: A Review

Abstract

Organic acids are key platform chemicals widely applied in food preservation, pharmaceuticals, agriculture, biodegradable polymers, and other industrial sectors. Sustainable production of these acids has gained increasing attention due to environmental concerns associated with chemical synthesis. Fungi represent efficient biofactories for organic acid production owing to their robust metabolism, substrate flexibility, and ability to secrete high levels of extracellular enzymes. This review focuses on fungal enzyme-mediated pathways involved in the biosynthesis of major organic acids, including citric acid, gluconic acid, oxalic acid, itaconic acid, lactic acid, and fumaric acid. Key enzymes, including glucose oxidase, citrate synthase, isocitrate lyase, oxaloacetate acetyl hydrolase, lactate dehydrogenase, and fumarase, play central roles in regulating metabolic flux toward organic acid accumulation. The review discusses metabolic pathways, regulatory mechanisms, strain improvement strategies, fermentation technologies, and the use of low-cost agro-industrial substrates. Major challenges such as product inhibition, by-product formation, downstream processing costs, and scale-up limitations are critically analysed. Furthermore, techno-economic considerations, including substrate cost, enzyme efficiency, fermentation optimisation, and industrial feasibility, are highlighted. Advances in metabolic engineering, omics tools, and biorefinery integration are also explored to enhance production efficiency and sustainability. This review provides comprehensive insights into fungal enzymatic systems driving organic acid biosynthesis and outlines future perspectives for economically viable and environmentally friendly industrial applications.