• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.312-316
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• 2004

Five strains, producing bacterial thermostable L-arabinose isomerase, were isolated from Korean soil samples obtained from compost under high temperature circumstances. Among these strains, the CBG-Al showed the highest L-arabinose isomerase activity at $60^\circ{C}$ and was selected as a D-tagatose producing strain from D-galactose. This strain was identified as Geobacillus thermodenitrificans based on the 16S rRNA analysis, and biological and biochemical characteristics. The isolated strain was aerobic, rod-shaped, Gram-positive, nonmotile, and an endospore-forming bacterium. No growth was detected in culture temperature below $40^\circ{C}$. The maximum growth temperature and maximum temperature of enzyme activity were $75^\circ{C}$ and $65^\circ{C}$, respectively. In metal ion effects, $Ca^{2+}$ was the most effective enzyme activator with the reaction rate by 150%. In a 5-1 jar fermentor with 3-1 MY medium, L-arabinose isomerase activity was growth-associated and pH decreased rapidly after the initial logarithmic phase.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.68-75
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• 2000

D-Tagatose is a potential bulking agent in food as a non-calorific sweetener. To produce D-tagatose from cheaper resources, plasmids harboring the L-arabinose isomerase gene (araA) from Escherichia coli was constructed because L-arabinose isomerase was previously suggested as an enzyme that mediates the bioconversion of galactose to tagatose as well as that of arabinose to ribulose. In the cultures of recombinant E.coli with pTC101, which harboring araA of E.coli, tagatose was produced from galactose in 9.9 % yield. The enzyme extract of E.coli containing pTC101 also converted galactose into tagatose in 96.4 % yield. For the economic production of D-tagatose, an L-arabinose isomerase of E.coli was immobilized using covalent binding on agarose. While the free L-arabinose isomerase produced tagatose with the rate of 0.48 mg/U$.$day, the immobilized one stably converted galactose into average 7.5 g/l$.$day of tagatose during 7 days with higher productivity of 0.87 mg/U$.$day. In the scaled up immobilized enzyme system, 99.9 g/l of tagatose was produced from galactose with 20 % equilibrium in 48 hrs. The process was stably repeated additional 2 times with tagatose production of 104.1 and 103.5 g/l.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.655-658
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• 2008

Although arabinose isomerase (E.C. 5.3.1.4), a commercial enzyme for edible tagatose bioconversion, can be expressed in an Escherichia coli system, this expression system might leave noxious by-products in food. To develop an eligible tagatose bioconversion with food-safe system, we compared the tagatose production activity of immobilized arabinose isomerase expressed in Bacillus subtilis (a host generally recognized as safe) with that of the enzyme expressed in E. coli. A 48% increase in tagatose production (4.3 g tagatose/L at $69.4\;mg/L{\cdot}hr$) was found using the B. subtilis-expressed immobilized enzyme system, compared to the E. coli-expressed enzyme system (2.9 g tagatose/L). The increased productivity with safety of the B. subtilis-expressed arabinose isomerase suggests that it is a more eligible candidate for commercial tagatose production.

• 한국약용작물학회:학술대회논문집
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• 2008.11a
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• pp.334-335
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• 2008

• Journal of Microbiology and Biotechnology
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• v.20 no.6
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• pp.1018-1021
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• 2010

Metallic and non-metallic isomerases can be used to produce commercially important monosaccharides. To determine which category of isomerase is more suitable as a template for directed evolution to improve enzymes for galactose isomerization, L-arabinose isomerase from Escherichia coli (ECAI; E.C. 5.3.1.4) and tagatose-6-phosphate isomerase from Staphylococcus aureus (SATI; E.C. 5.3.1.26) were chosen as models of a metallic and non-metallic isomerase, respectively. Random mutations were introduced into the genes encoding ECAI and SATI at the same rate, resulting in the generation of 515 mutants of each isomerase. The isomerization activity of each of the mutants toward a non-natural substrate (galactose) was then measured. With an average mutation rate of 0.2 mutations/kb, 47.5% of the mutated ECAIs showed an increase in activity compared with wild-type ECAI, and the remaining 52.5% showed a decrease in activity. Among the mutated SATIs, 58.6% showed an increase in activity, whereas 41.4% showed a decrease in activity. Mutant clones showing a significant change in relative activity were sequenced and specific increases in activity were measured. The maximum increase in activity achieved by mutation of ECAI was 130%, and that for SATI was 190%. Based on these results, the characteristics of the different isomerases are discussed in terms of their usefulness for directed evolution of non-natural substrate isomerization.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.495-495
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• 2005

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.606-607
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• 2005

• Microbiology and Biotechnology Letters
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• v.8 no.3
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• pp.173-180
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• 1980

A source of D-xylose was required for the enhanced production of D-glucose isomerase of Streptomyces sp. strain K-17. D-glucose supported the luxuriant growth of the organism as well as D-xylose, but D-glucose isomerase activity was hardly detected in the D-glucose-grown cells. When the D-glucose-grown cells were incubated aerobically for a few hours in 0.5% xylose solution in 0.05 M phosphate buffer, pH 7.0, it was found that inductive formation of D-glucose isomerase occurred in the cells without multiplication. In the non-growth phase of cells the inductive formation of D-glucose isomerase occurred because a source of nitrogen for the synthesis of enzymes was obtained from turnover of protein accumulated in cells. D-ribose, L-arabinose, D-glucose, D-mannose, citrate, succinate and tartrate could not induce the formation of D-glucose isomerase, but D-xylose could induce. Inductinn of D-glucose isomerase was repressed by D-glucose and its catabolites : glycerol, succinate and citrate. Inductive formation of the enzymes in the non-growth phase was stimulated by $Ba^{2+}$, $Mg^{2+}$ and $Co^{2+}$, and inhibited by C $u^{2+}$, C $d^{2+}$, A $g^{+}$and H $g^{2+}$. The synthesis of enzymes in the induction system composed of 0.5% xylose solution was disrupted by actinomycin D, streptomycin, chloramphenicol, kanamycin, tetracycline, p-chloromercuribenzo ate, arsenate and 2, 4-dinitrophenol, but not disrupted by mitomycin C and penicillin G.icillin G.

• Korean Journal of Microbiology
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• v.16 no.2
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• pp.47-61
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• 1978

Strptomyces albus T-12 which ahd been isolated and identified in the laboratory, was selected for the studies on the cultural conditions on the production of D-xylose iosmerase and the enzymological characteristics using the partially purified enzyme. The best results in the enzyme production came from D-xylose medium than wheat bran. The divalent metla ions as $Co^{2+},\;Fe^{2+},\;Zn^{2+}\;and\;Cu^{2+}$ retard or inhibit the cell-growth at the early stages of mycelia propagations, and T-12 strain is especially sensitive to $Co^{2+}$. After 60 hours of shaking cultivation at $30^{\circ}C$ and 200 rpm, a maximum enzyme activitz, 0.49 enzyme units, was obtained. Cell-free enzyme obtained from mycelia heat-treated in the prescence of 0.5mM $Co^{2+}$, showed a 2.4-fold increase in specific than the enzyme from untreated mycelia. The specific activity of the purified enzyme through Sephadex G-150 columm showed 180 fold to the crude enzyme. The effective activators of the enzyme appeared to be $Mg^{2+}\;and\;Co^{2+}$ ions, and it exhibited the maximal enzyme activity showed at pH 7.0 and at tempersture around $80^{\circ}C$ when $Mg^{2+}\;and\;Co^{2+}$ ions were added. The enzyme isomerized D-glucose, D-xylose, D-ribose, L-arabinose, D-mannose, and L-rhamnose in the present of $Mg^{2+}\;and\;Co^{2+}$ ions as an activatiors. $Mg^{2+}\;and\;Co^{2+}$ ions were non-competitively bound at different allosterix sites of enzyme molecule. $Mg^{2+}(5mM)\;or\;Co^{2+}(1.0mM)$ protected against the thermal denaturations of the enzyme activities. The michelis constant(Km) and $V_{max}$ values of the emzyme for D-glucose and D-xylose were 0.52M, $2.12{\mu}moles/ml{\cdot}min.\;and\;0.28M,\;0.65moles/ml{\cdot}min.$, respectively.

• Journal of Life Science
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• v.28 no.12
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• pp.1545-1553
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• 2018

The International Society of Rare Sugars (ISRS) defines rare sugars as monosaccharides and their derivatives that rarely occur in nature. Rare sugars have recently received much attention because of their many uses including low-calorie sweeteners, bulking agents, and antioxidants, and their various applications including as immunosuppressants in allogeneic rat liver transplantation, as potential inhibitors of various glycosidases and microbial growth, in ischemia-reperfusion injury repair in the rat liver, and in segmented neutrophil production without detrimental clinical effects. Because they rarely exist in nature, the production of rare sugars has been regarded as one of the most important research areas and, generally, they are produced by chemical synthesis. However, the production of rare sugars by bioconversion using enzymes from microorganisms has been receiving increased attention as an environmentally friendly alternative production method. In particular, D-allulose, D-allose, and D-tagatose are of interest as low-calorie sweeteners in various industries. To date, D-tagatose 3-epimerase, D-psicose 3-epimerase, and D-allulose 3-epimerase have been reported as D-allulose bioconversion enzymes, and L-rhamnose isomerase, Galactose 6-phosphate isomerase, and Ribose 5-phosphate isomerase have been identified as D-allose production enzymes. Elsewhere, D-tagatose has been produced by L-arabinose isomerase from various microorganisms. In this study, we report the production of D-allulose, D-allose, and D-tagatose by microorganism enzymes.