The role of pH transcription factor Appacc in upregulation of pullulan biosynthesis in Aureobasidium pullulans using potato waste as a substrate

pH is one of the important environmental factors affecting the growth, development and secondary metabolites of fungi. To better utilize potato waste for the production of pullulan by fermentation, in this study, the amino acid sequence and structural domain of pH transcription factor Appacc were analyzed using the bioinformatics methods. Appacc showed three typically conserved zinc finger domains, with the closest homology to Zymoseptoria brevis. The function of Appacc was characterized by Delta Appacc and OEXpacc mutants. The mycelium growth of Delta Apacc mutants was inhibited, especially, under alkaline conditions. Furthermore, the pullulan production of Delta Appacc mutant was reduced and the expression of pullulan synthetic genes also decreased. Moreover, the OEXpacc mutant further demonstrated that pacc could regulate the expression of pullulan synthesis genes. The yield of pullulan polysaccharide increased from 13.6 g/L to 17.8 g/L by direct fermentation without changing the pH of potato waste. These results suggest that Appacc played a vital role in the growth of Aureobasidium pullulans and that the production of pullulan from potato waste can be increased by overexpression of pacc gene.

Automated summary

pH is an important factor affecting fungi. The pH transcription factor Appacc plays a vital role in the production of pullulan from potato waste.