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.

由于废物管理问题，化石燃料的枯竭以及对可生物降解塑料的需求，将有机废物生物转化为增值产品的兴趣日益浓厚。乳酸广泛用于聚合物，食品，饮料，药品，化妆品和服装。然而，乳酸的大规模发酵的主要障碍是利用廉价的资源获得提高的产量，生产率和光学纯度。因此，我们回顾了使用廉价的发酵底物生产微生物乳酸的方法和回收技术。新的策略可以减轻与底物抑制，产物抑制，不良副产物，对有毒化合物的敏感性，混合糖的利用效率低下以及中和剂的过度使用有关的限制。使用混合培养物同时进行糖化和发酵，分离碳分解代谢抑制阻遏菌株并改变代谢途径，可以有效利用混合糖。通过共培养，维持高细胞密度并定期去除发酵培养基中积累的终产物，可以提高乳酸生产率。可以通过使用释放较少抑制剂的工程原料，通过使用耐受抑制剂的微生物以及开发基因工程菌株来消除对有毒化合物的抑制作用。由于较少的底物抑制，发现分批补料发酵优于其他操作模式。通过共培养，维持高细胞密度并定期去除发酵培养基中积累的终产物，可以提高乳酸生产率。可以通过使用释放较少抑制剂的工程原料，通过使用耐受抑制剂的微生物以及开发基因工程菌株来消除对有毒化合物的抑制作用。由于较少的底物抑制，发现分批补料发酵优于其他操作模式。通过共培养，维持高细胞密度并定期去除发酵培养基中积累的终产物，可以提高乳酸生产率。可以通过使用释放较少抑制剂的工程原料，通过使用耐受抑制剂的微生物以及开发基因工程菌株来消除对有毒化合物的抑制作用。由于较少的底物抑制，发现分批补料发酵优于其他操作模式。