Abstract
N-Acetylheparosan and chondroitin are increasingly needed as alternative sources of animal-derived sulfated glycosaminoglycans (GAGs) and as inert substances in medical devices and pharmaceuticals. The N-acetylheparosan productivity of E. coli K5 has achieved levels of industrial applications, whereas E.coli K4 produces a relatively lower amount of fructosylated chondroitin. In this study, the K5 strain was gene-engineered to co-express K4-derived, chondroitin-synthetic genes, namely kfoA and kfoC. The productivities of total GAG and chondroitin in batch culture were 1.2 g/L and 1.0 g/L respectively, which were comparable to the productivity of N-acetylheparosan in the wild K5 strain (0.6-1.2 g/L). The total GAG of the recombinant K5 was partially purified by DEAE-cellulose chromatography and was subjected to degradation tests with specific GAG-degrading enzymes combined with HPLC and 1H NMR analyses. The results indicated that the recombinant K5 simultaneously produced both 100-kDa chondroitin and 45-kDa N-acetylheparosan at a weight ratio of approximately 4:1. The content of chondroitin in total GAG partially purified was 73.2%. The molecular weight of recombinant chondroitin (100 kDa) was 5-10 times higher than that of commercially available chondroitin sulfate. These results indicated that the recombinant K5 strain acquired the chondroitin-producing ability without altering the total GAG productivity of the host.