Identification Of A Erythritol-producing Yeast And Cloning Of Its Erythrose Reductase Genes

Erythritol (1,2,3,4-butanetetrol) is a four-carbon sugar alcohol that has broadapplication in food, medicine, cosmetics, chemical and other fields for its puresweetness, low calory, good stability, high tolerance dose and some other properties.Erythritol is now commercially produced by fermentation of yeasts. In this study, aerythritol-producing yeast, strain BH010, was reported with its morphological andphysiological characteristics described, rDNA sequences analyzed and erythrosereductase genes cloned.Cultured in liquid medium consisting of30%glucose and1%yeast extract at30℃,150rpm for8d and then detected by HPLC, the major fermentation product waserythritol with small amount of byproducts presented, including glycerol and ribitol.Scanning electron micrography indicated that the cells were cylindrical to ellipticalwith an average size of5×10μm, occurring singly or in short chains with budding inthe top when growing in liquid medium. While pseudohyphae and roundblastoconidia were observed when cultivated in agar plate. The physiologicalcharacteristics of strain BH010were described through sugar fermentation, carbonsource assimilation, nitrogen source assimilation and some other biochemical tests.The D1/D2domain of the26S rDNA sequence, the ITS/5.8S rDNA sequence andthe18S rDNA sequence of strain BH010were amplified using the method of PCR,with the Genbank accession no. JQ798179，JQ798180and JQ798181, respectively.Analyzed with NCBI-BLAST algorithm, strain BH010was identified as a member ofthe Moniliella clade and was therefore named Moniliella sp. BH010.Erythrose reductase is a key enzyme in biosynthesis of erythritol by yeast. In thisstudy, the erythrose reductase genes and their corresponding cDNA sequences werecloned, sequenced, and analyzed, with the Genbank accession no. JQ798182andJQ798183. The amino acid sequences of erythrose reductase were deduced andaligned. BLAST analysis and multiple sequence alignment demonstrated thaterythrose reductase genes of strain BH010shared very high homology with that ofTrichosporonoides megachiliensis SNG-42except for the presence of introns. Thededuced amino acid sequences showed high homology to the aldo–keto reductasesuperfamily. This study reported a special erythritol-producing yeast and its rDNA sequences,which is helpful to gain insight into the taxonomy of erythritol-producing yeast.Moreover, the erythrose reductase genes from a Moniliella yeast were cloned with thepresence of introns reported for the first time, which is helpful to gain insight into themechanism of erythritol generation by yeast.