Abstract
Backgroundpoly(L-malic acid) (PMA) is a water-soluble polyester with many attractive properties in medicine and food industries, but the high cost of PMA fermentation has restricted its further application for large-scale production. To overcome this problem, PMA production from Jerusalem artichoke tubers was successfully performed. Additionally, a valuable exopolysaccharide, pullulan, was co-produced with PMA by Aureobasidum pullulans HA-4D.ResultsThe Jerusalem artichoke medium for PMA and pullulan co-production contained only 100 g/L hydrolysate sugar, 30 g/L CaCO3 and 1 g/L NaNO3. Compared with the glucose medium, the Jerusalem artichoke medium resulted in a higher PMA concentration (114.4 g/L) and a lower pullulan concentration (14.3 g/L) in a 5 L bioreactor. Meanwhile, the activity of pyruvate carboxylase and malate dehydrogenas was significantly increased, while the activity of α-phosphoglucose mutase, UDP-glucose pyrophosphorylase and glucosyltransferase was not affected. To assay the economic-feasibility, large-scale production in a 1 t fermentor was performed, yielding 117.5 g/L PMA and 15.2 g/L pullulan.ConclusionsIn this study, an economical co-production system for PMA and pullulan from Jerusalem artichoke was developed. The medium for PMA and pullulan co-production was significantly simplified when Jerusalem artichoke tubers were used. With the simplified medium, PMA production was obviously stimulated, which would be associated with the improved activity of pyruvate carboxylase and malate dehydrogenas.
Highlights
Poly(β-malic acid) (PMA) is a water-soluble polyester consisting of malic acid monomer
They found that A.pullulans ZX-10 could produce PMA as the major product at a high titer of 125.5 g/L, and pure malic acid was obtained from acid hydrolysis of PMA with a high recovery rate of 84%, this study offered an alternative method for malic acid production in the future
Jerusalem artichoke tuber is rich in carbohydrates, of which 70–90% (w/w) is inulin [14], and inulin can be hydrolyzed to monomeric sugars for microbial fermentation
Summary
Poly(β-malic acid) (PMA) is a water-soluble polyester consisting of malic acid monomer. Ljubimova et al have developed a new drug delivery system based on PMA and called it PolycefinsTM [3]. Microbial fermentation of PMA followed by acid hydrolysis provides a promising route for commercial malic acid production. Zou et al [2] investigated the feasibility of malic acid production derived from PMA. They found that A.pullulans ZX-10 could produce PMA as the major product at a high titer of 125.5 g/L, and pure malic acid was obtained from acid hydrolysis of PMA with a high recovery rate of 84%, this study offered an alternative method for malic acid production in the future
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