Pullulan productions by Aureobasidium pullulans CGMCC No.11602 were conducted using the initial culture (IC) medium and the optimized culture (OC) medium, respectively, in which pullulan with significantly different molecular weights was obtained. Under the IC medium condition, the pullulan molecular weight (Mw) reached 288,403 Da with a yield of 64.12 g/L after 96 h fermentation period. However, the pullulan molecular weight was much higher (Mw, 3,715,352 Da), while the yield of pullulan was lower (40.12 g/L) using the OC medium. The FTIR spectra indicated that pullulan produced using the IC and OC medium were similar. Transcriptome analysis showed that a total of 871 differentially expressed genes (DEGs) were screened and “N-glycan biosynthesis” and “other types of O-glycan biosynthesis” were the most highly represented differential metabolic pathways (DMPs). Specifically, the genes involved in the two DMPs consistently pointed to glucosyltransferase genes (GTF), all of which were up-regulated in the OC medium when compared with those in the IC medium. Further studies showed that the activity and the relative quantity (RQ) of GTF transcription were remarkable higher, which were coincident with the slower decrease in the molecular weight of pullulan in the OC medium than those in the IC medium during the late stage of fermentation. The results indicated that GTF may be involved in the regulation of pullulan molecular weight.
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This project was funded by the National Natural Science Foundation of China (21576160), Science and Technology Research Project of Shaanxi Province Academy of Sciences (2018nk-01), Shaanxi Science and Technology Department Science and Technology Planning Project (2017NY-192; 2018NY-152); The Scientific and Technologic Research Program of Shaanxi Academy of Sciences, China (No. 2018K- 09).
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Conflict of interest
The authors declare that there is no conflict of interests regarding the publication of this paper.
The supplementary information file (1) including primer sequence, significantly different metabolic pathways category, solubility curve and so on; The supplementary information file (2) including original data on differential gene expression from comparative transcriptome data. 1 (DOCX 226 KB)
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