Production of optically pure lactic acid by microbial fermentation: a review
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REVIEW
Production of optically pure lactic acid by microbial fermentation: a review Salma Aathika Abdur Rawoof1 · P. Senthil Kumar2 · Dai‑Viet N. Vo3 · Kubendran Devaraj1 · Yuvarani Mani1 · Thiruselvi Devaraj1 · Sivanesan Subramanian1 Received: 8 August 2020 / Accepted: 19 August 2020 © Springer Nature Switzerland AG 2020
Abstract Biotransformation of organic wastes into value-added products is gaining interest owing to waste management issues, exhaustion of fossil fuels and the demand for biodegradable plastics. Lactic acid is widely used for polymers, foods, beverages, medicines, cosmetics and clothing. However, the major obstacle in large-scale fermentation of lactic acid is achieving enhanced yield, productivity and optical purity with cheap resources. Therefore, we review methods and recovery techniques for production of microbial lactic acid using cheap fermentative substrates. New strategies allow to alleviate limitations associated with substrate inhibition, product inhibition, undesirable by-products, sensitivity to toxic compounds, inefficient utilization of mixed sugars and overuse of neutralizing agents. Efficient utilization of mixed sugars can be achieved with simultaneous saccharification and fermentation using mixed cultures, isolating carbon catabolic repression-negative strains and altering the metabolic pathway. Lactic acid productivity can be improved by co-culture, maintaining high cell density and periodically removing end-products accumulated in the fermentation medium. Inhibition by toxic compounds can be eliminated by using engineered feedstock which releases less inhibitors, by using inhibitor-tolerant microbes and by development of genetically engineered strains. Fed-batch fermentation was found to be better than other operation modes due to less substrate inhibition. Keywords Lactic acid · Biomass · Pre-treatment · Hydrolysis · Microbial fermentation · Lactic acid bacteria List of symbols T Temperature C Concentration Y Yield P Productivity ND Not described v v−1 Volume by volume C/N Carbon/nitrogen
* P. Senthil Kumar [email protected]; [email protected] * Sivanesan Subramanian [email protected] 1
Department of Applied Science and Technology, AC Tech, Anna University, Chennai, India
2
Department of Chemical Engineering, Sri Sivasubramaniya Nadar College of Engineering, Chennai, India
3
Center of Excellence for Green Energy and Environmental Nanomaterials (CE@GrEEN), Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
Introduction Microbial fermentation of commercially valuable products has been gaining more interests recently due to the rise in the demand for energy and the environmental problems induced by fossil fuels combustion. The development of new techniques to yield products with green technology is very essential for sustainable development (Hassan et al. 2020; Srivastava et al. 2020). Lactic acid is one such important product of interest due to its utilization in the manufacture of foods/beverages, medicines, cosmetics, leather
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