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.

Highly efficient production and characterization of the exopolysaccharides from a thermotolerant Bacillus sp.

One thermotolerant Bacillus strain SFLV-ZM107 which could produce large amounts of extracellular polysaccharides (EPS) at 50°C was identified as Bacillus licheniformis by 16S rDNA sequencing and physiological and biochemical experiments. The EPS was identified as levan fructan by monosaccharides determination, NMR, and FTIR. Strain SFLV-ZM107 can be grown in the range of 35-55°C and it is efficient to produce levan from 400 to 500 g l-1 of sucrose. The production of levan can reach 158 g l-1 in a 5 L tank fermentation with an initial sucrose concentration of 450 g l-1 at 50°C for 12 hours with a maximum productivity of 13.17 g l-1 h-1. To the best of our knowledge, the strains obtained in this study are the most productive and efficient, which has great prospects for industrial application.