A novel polygalacturonic acid bioflocculant REA-11 produced by Corynebacterium glutamicum: a proposed biosynthetic pathway and experimental confirmation

作者：Li Y; He N; Guan H; Du G; Chen J^*

来源：Applied Microbiology and Biotechnology, 2003, 63(2): 200-206.

DOI：10.1007/s00253-003-1365-9

• Corynebacterium glutamicum
• polysaccharide-protein bioflocculant
• galacturonic acid
• proposed biosynthetic pathway
• experimental confirmation

Corynebacterium glutamicum CCTCC M201005 produces a novel polygalacturonic acid bioflocculant, REA-11, consisting of galacturonic acid as the main structural unit. A biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 was proposed. Evidence for the biosynthetic pathway was provided by: (1) analyzing the response upon addition of UDP-glucose to the culture medium; (2) detecting the presence of several key intermediates in the pathway; and (3) correlating the activities of several key enzymes involved in the pathway with the yields of polygalacturonic acid. The production of polygalacturonic acid was improved by 24%, while the activities of UDP-galactose epimerase and UDP-galactose dehydrogenase were improved by 200% and 50%, respectively, upon addition of 100 muM UDP-glucose. In addition, the key intermediates in the proposed biosynthetic pathway, such as UDP-glucose, UDP-galactose, and UDP-glucuronic acid, were detected in cell-free extracts. Furthermore, the activities of UDP-glucose pyrophosphorylase (R-2=0.97), UDP-galactose epimerase (R-2=0.75) and UDP-galactose dehydrogenase (R-2=0.89) were well correlated with the yields of polygalacturonic acid when different sugars were used as sole carbon sources. Therefore, the biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 starts from phosphate-1-glucose, which was then converted to UDP-glucose by UDP-pyrophosphorylase. Predominantly, the UDP-glucose was converted to UDP-galactose by UDP-galactose epimerase; the latter was further converted to UDP-galacturonic acid by UDP-galactose dehydrogenase, which was presumably polymerized to polygalacturonic acid bioflocculant REA-11 by an unknown glucosyltransferase and a polymerase.

• 出版日期2003-12
• 单位江南大学