Metabolic engineering as a tool for enhanced lactic acid production

•Metabolic engineering can be used to address major challenges in lactic acid production.•Challenges include lactate purity, acid tolerance, carbon source and fermentation parameters.•Rational and evolutionary engineering are major metabolic engineering strategies.•Future developments are expected to enhance biomass utilization in lactate production.

Metabolic engineering is a powerful biotechnological tool that finds, among others, increased use in constructing microbial strains for higher lactic acid productivity, lower costs and reduced pollution. Engineering the metabolic pathways has concentrated on improving the lactic acid fermentation parameters, enhancing the acid tolerance of production organisms and their abilities to utilize a broad range of substrates, including fermentable biomass-derived sugars. Recent efforts have focused on metabolic engineering of lactic acid bacteria as they produce high yields and have a small genome size that facilitates their genetic manipulation. We summarize here the current trends in metabolic engineering techniques and strategies for manipulating lactic acid producing organisms developed to address and overcome major challenges in the lactic acid production process.