Microbial production of L-malate from renewable non-food feedstocks

L-malate is an intermediate of the tricarboxylic acid cycle which is naturally occurred in various microorganisms, and it has been widely applied in polymer, beverage and food, textile, agricultural and pharmaceutical industries. Driven by the pursuit of a sustainable economy, microbial production of L-malate has received much attention in last decades. In this review, we focus on the utilization of wastes and/or by-products as feedstocks for the microbial production of L-malate. Firstly, we present the recent developments on the natural or engineered metabolic pathways that dedicate to the biosynthesis of L-malate, and also provide a comprehensive discussions on developing high-efficient producers. Then, the recent achievements in microbial production of L-malate from various carbon sources were concluded and discussed. Furthermore, some abundant non-food feedstocks which have been used for microbial production of other chemicals were reviewed, as they may be potential candidate feedstock for L-malate production in future. Finally, we outlined the major challenges and proposed further improvements for the production of L-malate.