Functional Identification of the Dextransucrase Gene of Leuconostoc mesenteroides DRP105.

Renpeng Du,Zhijiang Zhou,Ye Han

doi:10.3390/ijms21186596

Renpeng Du, Zhijiang Zhou + Show 1 more

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https://doi.org/10.3390/ijms21186596

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Abstract

Leuconostoc mesenteroides DRP105 isolated from Chinese sauerkraut juice is an intensive producer of dextran. We report the complete genome sequence of Leu. mesenteroides DRP105. This strain contains a dextransucrase gene (dsr) involved in the production of dextran, possibly composed of glucose monomers. To explore the dextran synthesis mechanism of Leu. mesenteroides DRP105, we constructed a dsr-deficient strain derived from Leu. mesenteroides DRP105 using the Cre-loxP recombination system. The secondary structure prediction results showed that Leu. mesenteroides DRP105 dextransucrase (Dsr) was coded by dsr and contained 17.07% α-helices, 29.55% β-sheets, 10.18% β-turns, and 43.20% random coils. We also analyzed the dextran yield, monosaccharide change, organic acid, and amino-acid content of Leu. mesenteroides DRP105 and Leu. mesenteroides DRP105−Δdsr. The result showed that the lack of dsr changed the Leu. mesenteroides DRP105 sugar metabolism pathway, which in turn affected the production of metabolites.

Highlights

Exopolysaccharides (EPS) are used in medicine, food, and other industrial products due to their unique chemical, physical, and biological activities [1]
When the plasmid pNZTS-Cre was transformed into Leu. mesenteroides DRP105, remediated recombination was confirmed by PCR amplification with the primer dsr-1-F/dsr-1-R as above. These results suggested that the dsr gene was completely deleted in Leu. mesenteroides DRP105
As Leu. mesenteroides DRP105−Δdsr did not effectively use the sucrose, the sucrose content was significantly higher than that of Leu. mesenteroides DRP105 (p < 0.05) (Figure 10B), and the contents of glucose and fructose were significantly lower than that of Leu. mesenteroides DRP105 (Figure 10C,D), indicating that the dsr gene plays a key role in the metabolism

Summary

Introduction

Exopolysaccharides (EPS) are used in medicine, food, and other industrial products due to their unique chemical, physical, and biological activities [1]. One of the most important examples of microbial EPS is glucan, as produced by Leuconostoc mesenteroides, which was found to have a wide range of applications in medicine. Given the wide commercial use of dextran, sufficient information must be obtained regarding the characteristics of EPS-producing strains [4]. Studies show that Dsrs from different LABs have similar biochemical properties and structural characteristics [5]. These different Dsrs can form different glucan repeating units [6], which in turn affect the function of glucan. The mechanism of Dsr regulation during LAB glucan synthesis is not clear. Genes that regulate dextran repeat unit synthesis, chain length, aggregation, and export are relatively conserved. More than 30 confirmed dextransucrase gene (dsr) have been reported [7], and the catalytic performance of Dsr from different sources is very different, which means the corresponding Dsrs have many different morphologies

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