Light calcium carbonate improves pullulan biosynthesis by Aureobasidium pullulans under high concentration of sugar

The effects of light calcium carbonate (CaCO3) on pullulan biosynthesis by Aureobasidium pullulans NCPS2016 were investigated. Light CaCO3 enhanced pullulan production by 12.4 % when added to the low concentration of fructose broth compared with K2HPO4. Pullulan production was further improved when increasing both the concentrations of light CaCO3 and fructose. Compared to K2HPO4, light CaCO3 improved the activities of UDP-glucose pyrophosphorylase, alpha-phosphoglucose mutase, UDP-glucosyltransferase, and glucosyltransferase rele-vant to pullulan biosynthesis, and the gene transcriptional levels of UDP-glucose pyrophosphorylase, alpha-phos-phoglucose mutase, UDP-glucosyltransferase, and glucose kinase were enhanced. During 30-liter fermentation, 144.3 g/L of purified pullulan was produced from 200 g/L of fructose and 15 g/L of light CaCO3 within 168 h, with the yield and productivity of 0.72 g/g and 0.86 g/L/h respectively. This is the first report that light CaCO3 improves pullulan production significantly.