A High Molecular Weight Polymalate is Synthesized by the Whole Genome Duplicated Strain Aureobasidium Melanogenum OUC

Polymalate (PMA) produced by the whole genome duplicated strain Aureobasidium melanogenum OUC had a high molecular weight (Mw) of 3.9 × 10 Da while the Mw of PMA produced by A. melanogenum ATCC62921 was 3.8 × 10 Da. Therefore, the purified PMA produced by A. melanogenum OUC could form hydrogel and film and the precipitated Ca-PMA looked like noodle whereas the purified PMA produced by A. melanogenum ATCC62921 could not form such a hydrogel and a film and the precipitated PMA was powder-like. The high Mw PMA biosynthesis in A. melanogenum OUC was also controlled by the PMA synthetase. However, it was still unclear why the PMA synthetase in A. melanogenum OUC could catalyze the high Mw PMA biosynthesis. Both removal of two copies of the PKS genes and overexpression of the PYC1 gene, the VGB gene and the CRZ2 gene rendered the new transformant Crz46 to produce 34.6 ± 0.3 g/L of extracellular Ca-PMA with Mw of 4.9 × 10 Da while its native A. melanogenum OUC only produced 17.2 ± 0.3 g/L of Ca-PMA. During the 10-Liter fermentation, 35.6 ± 1.2 g/L of Ca-PMA and 13.9 g/Lof cell mass were produced within 168 h, leading to the yield of 0.36 g/g of glucose and the productivity of 0.21 g/L/h. This was the first time to report that the whole genome duplicated strain A. melanogenum OUC and its engineered mutants could produce the high Mw PMA.