Recent advances in biosynthesis mechanisms and yield enhancement strategies of erythritol.

Erythritol is a four-carbon sugar alcohol naturally produced by microorganisms as an osmoprotectant. As a new sugar substitute, erythritol has recently been popular on the ingredient market because of its unique nutritional characteristics. Even though the history of erythritol biosynthesis dates from the turn of the twentieth century, scientific advancement has lagged behind other polyols due to the relative complexity of making it. In recent years, biosynthetic methods for erythritol have been rapidly developed due to an increase in market demand, a better understanding of metabolic pathways, and the rapid development of genetic engineering tools. This paper reviews the history of industrial strain development and focuses on the underlying mechanism of high erythritol production by strains gained through screening or mutagenesis. Meanwhile, we highlight the metabolic pathway knowledge of erythritol biosynthesis in microorganisms and summarize the metabolic engineering and research progress on critical genes involved in different stages of the synthetic pathway. Lastly, we talk about the still-contentious issues and promising future research directions that will help break the erythritol production bottleneck and make erythritol production greener and more sustainable.