(41/50) Crystallization and preliminary X-ray analysis of 5-keto-D-gluconate reductase from Gluconobacter suboxydans IFO12528 complexed with 5-keto-D-gluconate and NADPH.


(42/50) Selective, high conversion of D-glucose to 5-keto-D-gluoconate by Gluconobacter suboxydans.

Selective, high-yield production of 5-keto-D-gluconate (5KGA) from D-glucose by Gluconobacter was achieved without genetic modification. 5KGA production by Gluconobacter suffers byproduct formation of 2-keto-D-gluconate (2KGA). By controlling the medium pH strictly in a range of pH 3.5-4.0, 5KGA was accumulated with 87% conversion yield from D-glucose. The pH dependency of 5KGA formation appeared to be related to that of gluconate oxidizing activity.  (+info)

(43/50) Formation of 4-keto-D-aldopentoses and 4-pentulosonates (4-keto-D-pentonates) with unidentified membrane-bound enzymes from acetic acid bacteria.

In our previous study, a new microbial reaction yielding 4-keto-D-arabonate from 2,5-diketo-D-gluconate was identified with Gluconacetobacter liquefaciens RCTMR 10. It appeared that decarboxylation and dehydrogenation took place together in the reaction. To analyze the nature of the reaction, investigations were done with the membrane fraction of the organism, and 4-keto-D-arabinose was confirmed as the direct precursor of 4-keto-D-arabonate. Two novel membrane-bound enzymes, 2,5-diketo-D-gluconate decarboxylase and 4-keto-D-aldopentose 1-dehydrogenase, were involved in the reaction. Alternatively, D-arabonate was oxidized to 4-keto-D-arabonate by another membrane-bound enzyme, D-arabonate 4-dehydrogenase. More directly, D-arabinose oxidation was examined with growing cells and with the membrane fraction of G. suboxydans IFO 12528. 4-Keto-D-arabinose, the same intermediate as that from 2,5-diketo-D-gluconate, was detected, and it was oxidized to 4-keto-D-arabonate. Likewise, D-ribose was oxidized to 4-keto-D-ribose and then it was oxidized to 4-keto-D-ribonate. In addition to 4-keto-D-aldopentose 1-dehydrogenase, the presence of a novel membrane-bound enzyme, D-aldopentose 4-dehydrogenase, was confirmed in the membrane fraction. The formation of 4-keto-D-aldopentoses and 4-keto-D-pentonates (4-pentulosonates) was finally confirmed as reaction products of four different novel membrane-bound enzymes.  (+info)

(44/50) Enzymatic synthesis of 4-pentulosonate (4-keto-D-pentonate) from D-aldopentose and D-pentonate by two different pathways using membrane enzymes of acetic acid bacteria.

4-Keto-D-arabonate (D-threo-pent-4-ulosonate) and 4-keto-D-ribonate (D-erythro-pent-4-ulosonate) were prepared from D-arabinose and D-ribose by two successive reactions of membrane-bound enzymes, D-aldopentose 4-dehydrogenase and 4-keto-D-aldopentose 1-dehydrogenase of Gluconobacter suboxydans IFO 12528. Alternatively, they were prepared from D-arabonate and D-ribonate with another membrane-bound enzyme, D-pentonate 4-dehydrogenase. Analytical data confirmed the chemical structures of the 4-pentulosonates prepared. This is the first report of successful enzymatic synthesis of 4-pentulosonates.  (+info)

(45/50) Draft genome sequence of Gluconobacter morbifer G707T, a pathogenic gut bacterium isolated from Drosophila melanogaster intestine.


(46/50) Synthesis and interfacial properties of monoacyl glyceric acids as a new class of green surfactants.

Glyceric acid (GA) is one of the most promising functional hydroxyl acids, and it is abundantly obtained from glycerol by a bioprocess using acetic acid bacteria. In this study, several monoacyl GAs were synthesized by esterification of GA and saturated fatty acyl chlorides (C12, C14, C16, and C18), forming a new class of bio-based surfactants. By the present method, a mixture of two isomers, namely 2-O-acyl and 3-O-acyl GAs, was produced, in which the 2-O-acyl derivatives were obtained as a major product. These isomers were isolated, and their surface-active properties were investigated for the first time. The surface tensions of 2-O-acyl GAs with different chain lengths were determined by the Wilhelmy method. At concentrations below 10(-4) M, the 2-O-acyl GAs exhibited higher surface-active properties compared to commercially available synthetic surfactants. For example, 2-O-lauroyl GA reduced the surface tension of water to around 25 mN/m above the critical micelle concentration (3.0x10(-4) M). In addition, 2-O-acyl derivatives showed higher surface-tension-lowering activity than 3-O-acyl GAs. The monoacyl GAs synthesized herein can potentially be used as "green surfactants."  (+info)

(47/50) Characterization of genes involved in D-sorbitol oxidation in thermotolerant Gluconobacter frateurii.

Further upstream of sldSLC, genes for FAD-dependent D-sorbitol dehydrogenase in Gluconobacter frateurii, three additional genes (sldR, xdhA, and perA) are found: for a transcriptional regulator, NAD(P)-dependent xylitol dehydrogenase, and a transporter protein, a member of major facilitator superfamily, respectively. xdhA and perA but not sldR were found to be in the same transcriptional unit. Disruption of sldR resulted in a dramatic decrease in sldSLC promoter activity, indicating that it is an activator for sldSLC expression. The recombinant protein of XdhA expressed in Escherichia coli showed NAD-dependent dehydrogenase activities with xylitol and D-sorbitol, but a mutant strain defective in this gene showed similar activities with both substrates as compared to the wild-type strain. Nonetheless, the growth of the xdhA mutant strain on D-sorbitol and xylitol was retarded, and so was that of a mutant strain defective in perA. These results indicate that xdhA and perA are involved in assimilation of D-sorbitol and xylitol.  (+info)

(48/50) Nectar bacteria, but not yeast, weaken a plant-pollinator mutualism.