(256c) Production of Polymalic Acid (PMA) and Malic Acid from Food Processing Byproducts By Aureobasidium Pullulans

PMA is a biodegradable and biocompatible water-soluble polymer with potential application as prodrugs or drug carriers in biomedical industry. PMA can be readily hydrolyzed to malic acid, which is widely used as an acidulant in foods and pharmaceuticals. In this study, PMA is produced by Aureobasidium pullulans from agricultural wastes such as soybean hull, soybean molasses, and sugarcane juice. PMA production from soybean hull hydrolysate supplemented with corn steep liquor (CSL) gave a malic acid yield of ∼0.4 g/g at a productivity of ∼0.5 g/L·h. ZX-10 can also ferment soy molasses without enzyme hydrolysis, converting all carbohydrates including the raffinose family oligosaccharides to PMA, giving a high titer (71.9 g/L) and yield (0.69 g/g) at a productivity of 0.29 g/L·h in fed-batch fermentation under nitrogen limitation, and a higher productivity of 0.64 g/L·h was obtained in repeated batch fermentation with cell recycle and CSL supplementation. Sugarcane juice can be used as an economical substrate without any pretreatment or nutrients supplementation. For PMA production from sugarcane juice, a high PMA titer of 116.3 g/L and yield of 0.41 g/g were achieved in fed-batch fermentation, and a high productivity of 0.66 g/L·h was achieved in repeated-batch fermentation with cell recycle. Cost analysis shows that malic acid can be produced at $1.10/kg from soy molasses, $1.33/kg from sugarcane juice, $1.37/kg from corn, and $1.74/kg from soybean hull. At the market price of $1.75/kg, malic acid production from soy molasses and sugarcane juice via PMA fermentation offers an economically competitive process for industrial production of bio-based malic acid.