Genetic Modification of the Marine-Isolated Yeast Aureobasidium melanogenum P16 for Efficient Pullulan Production from Inulin.

In this study, in order to directly and efficiently convert inulin into pullulan, the INU1 gene from Kluyveromyces maximum KM was integrated into the genomic DNA and actively expressed in the high pullulan producer Aureobasidium melanogenum P16 isolated from the mangrove ecosystem. After the ability to produce pullulan from inulin by different transformants was examined, it was found that the recombinant strain EI36, one of the transformants, produced 40.92 U/ml of inulinase activity while its wild-type strain P16 only yielded 7.57 U/ml of inulinase activity. Most (99.27 %) of the inulinase produced by the recombinant strain EI36 was secreted into the culture. During the 10-l fermentation, 70.57 ± 1.3 g/l of pullulan in the fermented medium was attained from inulin (138.0 g/l) within 108 h, high inulinase activity (42.03 U/ml) was produced within 60 h, the added inulin was actively hydrolyzed by the secreted inulinase, and most of the reducing sugars were used by the recombinant strain EI36. This confirmed that the genetically engineered yeast of A. melanogenum strain P16 was suitable for direct pullulan production from inulin.