Efficient Production of Polymalic Acid by a Novel Isolated Aureobasidium pullulans Using Metabolic Intermediates and Inhibitors

Polymalic acid (PMA) is a linear anionic polyester composed of l-malic acid monomers, which have potential applications as drug carriers, surgical suture, and biodegradable plastics. In this study, a novel strain of Aureobasidium pullulans var. melanogenum GXZ-6 was isolated and identified according to the morphological observation and deoxyribonucleic acid internal-transcribed spacer sequence analysis, and the product of PMA was characterized by FT-IR, 13C-NMR, and 1H-NMR spectra. The PMA titer of GXZ-6 reached 62.56 ± 1.18 g L−1 with productivity of 0.35 g L−1 h−1 using optimized medium with addition of metabolic intermediates (citrate and malate) and inhibitor (malonate) by batch fermentation in a 10-L fermentor. Besides that the malate for PMA synthesis in GXZ-6 might mainly come from the glyoxylate cycle, based on results, citrate, malate, malonate, and maleate increased while succinate and fumarate inhibited the production of PMA, which was different from that of other A. pullulans. This study provided a potential strain and a simple metabolic control strategy for high-titer production of PMA and shared novel information on the biosynthesis pathway of PMA in A. pullulans.