(715b) Production of Polymalic Acid (PMA) From Biomass Hydrolysates By Aureobasidium Pullulans

PMA is a biocompatible, biodegradable and bioresorbable water-soluble polymer composed of malic acid. PMA can be readily functionalized by the large number of carboxyl groups present in the molecule. Therefore, PMA has great potential to be used as prodrugs or drug carriers. Currently, PMA can be produced by either chemical synthesis or microbial fermentation. Compared to chemical ways, bioprocess represents a better PMA source due to the advantages of higher enantiomerical purity in products, flexibility to feedstock and being more environmentally friendly. Previously, we have developed an efficient fermentative process for high-level production of PMA from Aureobasidium pullulans strain ZX-10 with high titer of 123 g/L. However, the increasing cost of raw materials such as glucose and water may significantly hamper the economical competitiveness of PMA fermentation.

In this work, we achieved efficient PMA production with decent titer (>20g/L) and yield (0.5~0.8g/g sugar) from agricultural biomass substrates such as cotton stalk, cassava bagasse and soybean hull hydrolysates and soybean molasses. Among these substrates, oligosaccharide contained in soybean molasses including stachyose and raffinose can be directly converted to PMA without pretreatment while soybean hull hydrolysate gave the highest titer (38 g/L) and yield (0.8g/g sugar). Therefore, these results showed that using inexpensive substrates such as agricultural biomass hydrolysate provides an efficient and economical way for PMA production and is promising for industrial application.