Jungdon Bae

A novel bioreactor with an internal adsorbent for integrated fermentation and recovery of prodigiosin-like pigment produced from Serratia sp. KH-95

A novel bioreactor with an internal adsorbent was developed for the simultaneous fermentation and recovery of prodigiosin-like pigment produced from Serratia sp. KH-95 as a model product in one bioreactor. The pigment concentration recovered in the internal adsorbent was 13.1 g l−1, which was 1.8-fold higher than that obtained in a bioreactor with an external adsorbent.

A practical enzymatic synthesis of UDP sugars and NDP glucoses.

Nucleoside diphosphate (NDP) sugar pyrophosphorylases (NPs) catalyze the bioconversion of sugar-1-phosphates (Su1Ps) and nucleoside triphosphates (NTPs) to NDP sugars. Various glycosyltransferases specifically transfer these activated monosaccharide residues onto a free hydroxyl or amino group on an acceptor molecule to synthesize bioactive metabolites such as glycogen, trehalose, lipopolysaccharides, and peptidoglycans, which are present in the bacterial cell wall. Furthermore, many pharmaceutically relevant natural products are glycosylated secondary metabolites, which are thought to have potential for the development of novel glycorandomization therapeutics. Although chemical syntheses of a few NDP sugars have been reported by various groups, the methods used were complicated by the laborious maneuvering of protecting groups in order to achieve regioselectivity. By contrast, NPs from natural sources catalyze regioselective phosphorylation by modulation of the metabolic intermediates. For these reasons, a variety of in vitro synthetic routes to NDP sugars by a salvage or a de novo pathway have been designed and implemented. In view of the synthetic availability of high-energy donor NDP sugars for glycosyltransferases, we report the synthesis of UDP sugars and NDP glucoses by recombinant Thermus caldophilus GK24 (Tca) UDP-sugar pyrophosphorylase (UP) and the substrate specificity of the enzyme toward various NTPs and Su1Ps. The Tca usp gene (GeneBank accession no. : AAV80705), which encodes UP, was cloned and inserted into the pKK223-3 vector to construct plasmid pGLM. The tetrameric UP protein was overexpressed at an optimal temperature of 70 8C in Escherichia coli MV1184 harboring pGLM (see the Supporting Information), and purified by heat precipitation and one-step anion-exchange column chromatography (Figure 1). The presence of Mg and Mn at an appropriate concentration was required for Tca UP activity; Co 2+ and Ni were less effective (see the Supporting Information). A thermostability test showed that Tca UP was very stable at 70 8C for 1 h (see the Supporting Information).