Abstract: The effect of sodium chloride (NaCl) on pullulan biosynthesis by Aureobasidium pullulans CCTCC M 2012259 in shaking flasks was investigated. NaCl was found to be conducive to pullulan production, but was unfavorable to maintain the molecular mass of pullulan at a high level. The results of batch fermentation showed that pullulan production increased by 17.6% in the experimental group (3 g/L NaCl), while the molecular mass of pullulan finally obtained decreased by 55.8%, as compared to the control group (0 g/L NaCl). Based on the RNA sequencing (RNA-Seq) analysis of A. pullulans, a total of 659 significantly differentially expressed genes (DEGs) were identified between the two groups, of which 227 genes were up-regulated while the remaining 432 were down-regulated in the experimental group. Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of these DEGs indicated that NaCl regulated the expression of genes encoding certain hydrolases as well as ion and small molecule-binding proteins. These genes participated in carbohydrate, starch and sucrose metabolism, and glycolysis/gluconeogenesis, resulting in significant changes in the production and molecular mass of pullulan.

Key words: Aureobasidium pullulans; pullulan; sodium chloride; RNA sequencing; differentially expressed genes