• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1078-1082
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• 2019

Poly-${\gamma}$-glutamate (${\gamma}$-PGA) has various applications due to its desirable characteristics in terms of safety and biodegradability. Previous studies have been conducted on ${\gamma}$-PGA hydrogels produced by ${\gamma}$-ray irradiation, but these hydrogels have proved unstable in solutions. This study was conducted to enable the ${\gamma}$-PGA hydrogel to maintain a stable form in solutions. The ${\gamma}$-PGA mixture for UV-irradiation was prepared with a cross-linker (N,N,N-trimethyl-3-[(2-methylacryloyl)amino]propan-1-aminium). Both ${\gamma}$-PGA hydrogels' characteristics, including stability in solutions, were examined. The UV-irradiated ${\gamma}$-PGA hydrogel maintained a stable form during the nine weeks of the study, but the ${\gamma}$-ray irradiated hydrogel dissolved after one week.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.4
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• pp.289-295
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• 2005

In this study, the cultural medium used for the efficient production of $\gamma$-PGA with a newly isolated Bacillus sp. RKY3 was optimized. It was necessary to supplement the culture medium with L-glutamic acid and an additional carbon source in order to induce the effective production of $\gamma$-PGA. The amount of $\gamma$-PGA increased with the addition of L-glutamic acid to the medium. The addition of 90 g/L L-glutamic acid to the medium resulted in the maximal yield of $\gamma$-PGA (83.2 g/L). The optimum nitrogen source was determined to be peptone, but corn steep liquor, a cheap nutrient, was also found to be effective for $\gamma$-PGA production. Both the $\gamma$-PGA production and cell growth increased rapidly with the addition of small amounts of $K_2HPO_4$ and $MgSO_4\cdot7H_{2}O$. Bacillus sp. RKY3 appears to require $Mg^{2+}$, rather than $Mn^{2+}$, for $\gamma$-PGA production, which is distinct from the production protocols associated with other, previously reported bacteria. Bacillus sp. RKY3 may also have contributed some minor $\gamma$-PGA depolymerase activity, resulting in the reduction of the molecular weight of the produced $\gamma$-PGA at the end of fermentation.

• Journal of Microbiology and Biotechnology
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• v.21 no.7
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• pp.766-775
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• 2011

We investigated the effect of high molecular weight polygamma- glutamic acid (hm ${\gamma}$-PGA) on adiposity and lipid metabolism of rats in the presence of an obesity-inducing diet. Thirty-two Sprague-Dawley rats were fed either a normal-fat (11.4% kcal fat, NFC) or high-fat (51% kcal fat, HFC) diet. After 5 weeks, half of each diet-fed group was treated with hm ${\gamma}$-PGA (NFP or HFP) for 4 weeks. The HFC group had significantly higher body weight, visceral fat mass, fasting serum levels of total cholesterol, LDL cholesterol, and leptin, and lower serum HDL cholesterol level compared with those of the NFC group (p < 0.05). Treatment with hm ${\gamma}$-PGA decreased body weight gain and perirenal fat mass (p<0.05), fasting serum total cholesterol, and mRNA expression of glucose-6- phosphate dehydrogenase (G6PD), regardless of dietary fat contents (p < 0.01). However, hm ${\gamma}$-PGA increased serum HDL cholesterol in the HFC group (p < 0.05). In vitro, 3-hydroxy-3-methylglutaryl coenzyme-A (HMGCoA) reductase activity was suppressed by the addition of hm ${\gamma}$-PGA. In agreement with observations in animal study, the supplementation of hm ${\gamma}$-PGA (150 mg/day) to 20 female subjects in an 8-week double-blind, placebocontrolled study resulted in a tendency to decrease total cholesterol and LDL cholesterol concentrations. We thus conclude that dietary supplementation of hm ${\gamma}$-PGA may act as a hypocholestrolemic agent, secondary to its inhibitor effect on HMG-CoA reductase, and decrease abdominal adiposity by decreasing hepatic lipogenesis. The present study is an important first step in establishing the effect of hm ${\gamma}$-PGA on cholesterol levels in rats and humans.

• KSBB Journal
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• v.8 no.3
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• pp.217-223
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• 1993

Methods for production of ${\gamma}$-Polyglutamic acid( ${\gamma}$-PGA ) by an alkalophilic Alcaligenes sP. were investigated for batch and continuous culture processes. Both quantity and productivity of ${\gamma}$-PGA by Alcaligenes sp. in batch culture were gradually increased with the increase of glucose concentration up to 50g/l , but the maximal production yield of 63% was obtained at 10g/l of glucose concentration. The highest specific growth rate was about $0.25hr^{-1}$ at 50un of glucose concentration, and substrate inhibition was observed at above 50g1f of glucose concentration. The highest ${\gamma}$-PGA formation about 11g/l in a batch system was obtained at 31'C, pH 10.0 and 87rpn Productivity of 2.80g/l/hr for continuous cultivation was 9 times higher than the productivity for batch cultivation.

• Microbiology and Biotechnology Letters
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• v.38 no.1
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• pp.53-63
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• 2010

As one of the mucous components of Cheonggukjang, traditional fermented soybean paste, $\gamma$-PGA is a natural substance with diverse functions. In this paper, an in-vivo experiment has been performed using NC/Nga mice in order to find out the efficacy of $\gamma$-PGA in human atopic dermatitis. The NC/Nga mice with BMAC-induced atopic dermatitis were administered $\gamma$-PGA (PGA-HM) with 300 kDa and low-molecular $\gamma$-PGA (PGA-LM), respectively. As a result, a significant decrease in clinical skin severity score was detected in the group that was administered PGA-LM. In terms of serum IgE levels, a significant decline was observed in PGA-LM, compared to the control group. The serum IgG1 levels also decreased more in PGA-LM than in the control group. However, no significant difference was observed in both groups. To witness the induction of $CD4^+CD25^+foxp3^+$ Treg cells, mRNA was sampled from the back of PGA-HM- and PGA-LM-administered NC/Nga mice with atopic dermatitis. In terms of the production amount of foxp3 mRNA, which was measured in real-time PCR, the group that was administered PGA-LM was twice as high as the control group. According to a biopsy on the skin on the backs of the mice, the experimental group was also far lower than the control group in terms of epidermis thickness, mast cell infiltration and the number of $CCR3^+$ cells. Therefore, it has been confirmed that the atopic dermatitis symptoms decreased more in the PGA-LM-administered NC/Nga mice than the PGA-HM-administered group by facilitating $CD4^+CD25^+foxp3^+$ Treg cells and suppressing the activity of eosinophils and production of IgE and pro-inflammatory cytokines.

• Nutrition Research and Practice
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• v.4 no.1
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• pp.23-29
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• 2010

Poly-gamma-glutamic acid ($\gamma$-PGA) is a mucilaginous and biodegradable compound produced by Bacillus subtilis from fermented soybeans, and is found in the traditional Korean soy product, cheongkukjang. This study was carried out to evaluate the effects of $\gamma$-PGA from a food source on the concentration of the neurotransmitter GABA and its metabolic precursor glutamate in diet-induced obese rats. Eight-week old male Sprague-Dawley rats (n=60) were used. The rats were divided into two groups and obesity was induced by providing either a 10% control fat or 45% high fat diet for 5 weeks. The rats were then blocked into 6 groups and supplemented with a 0.1% $\gamma$-PGA diet for 4 weeks. After sacrifice, brain and serum GABA and glutamate concentrations were analyzed by high performance liquid chromatography with fluorometric detection. The rats fed the high fat diet had significantly increased body weights. $\gamma$-PGA supplementation significantly increased serum concentrations of glutamate and GABA in the control fat diet groups while this effect was not found in the high fat groups. In the brain, glutamate concentrations were significantly higher in the $\gamma$-PGA supplemented groups both in rats fed the normal and high fat diets than in the no $\gamma$-PGA controls. GABA concentrations showed the same tendency. The results indicated that $\gamma$-PGA intake increased GABA concentrations in the serum and brain. However, the effects were not shown in obese rats.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.251-257
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• 2006

The components of the media used to elicit the biosynthesis of $poly-{\gamma}-glutamic$ acid $({\gamma}-PGA)$ by Bacillus subtilis ZJU-7 were investigated, particularly the carbon and nitrogen sources Of the 7 carbon sources investigated, sucrose induced the highest rate of ${\gamma}-PGA$ productivity; among the nitrogen sources, tryptone had the best effect for ${\gamma}-PGA$ production. A $2^{6-2}$ fractional factorial design was used to screen factors that influence ${\gamma}-PGA$ production significantly, and a central composite design was finally adopted to formulate the optimal medium. ${\gamma}-PGA$ productivity improved approximately 2-fold when the optimal medium was used compared with the original nonoptimized medium, and volumetric productivity reached a maximum of 58.2 g/L after a 24-h cultivation period.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.59-65
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• 2005

Poly-${\gamma}$-glutamic acid (PGA) is an unusual anionic polypeptide and has great potential as an environmentally and industrially significant biodegradable material. A new ${\gamma}$-PGA producer, Bacillus mesentericus MJM1, with high production capacity was isolated from Korean domestic Chungkuckjang bean paste. It produced ${\gamma}$-PGA at the level of 10 g/l in suitable media. The viscosities of 5% initially extracted mucin and purified ${\gamma}$-PGA solutions were 660 cps and 600 cps, respectively. The produced ${\gamma}$-PGA polymer consisted of 2,000 glutamic acid residues with even proportion of L and D types with molecular mass of about 200- 300 kDa. Bacillus mesentericus MJM1 displayed ${\gamma}$-glutamyltranspeptidase (${\gamma}$-GTP) activity that is known to play a key role in ${\gamma}$-PGA biosynthesis. The ${\gamma}$-GTP coding region was located on the plasmid of 5.8 kb. The plasmid, named pMMH1, is a rolling-circle replication (RCR) plasmid and additionally contained a replication origin and type I signal peptidase (sipP) coding region.

• Journal of Microbiology and Biotechnology
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• v.23 no.6
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• pp.785-793
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• 2013

We studied the effects of 2 different dosages of high-molecular-weight poly-${\gamma}$-glutamic acid (hm ${\gamma}$-PGA) derived from Bacillus subtilis chungkookjang on lipid metabolism in a high-fructose diet-induced hypertriglyceridemic animal model. For 4 weeks, rats were fed either AIN-93 diet (normal control, NC; n = 10) or modified AIN-93 diet in which cornstarch was substituted with 63% fructose (n = 30) to induce hypertriglyceridemia. After 4 weeks, the hypertriglyceridemic rats were treated with daily oral doses of 0 mg (hypertriglyceridemic control, HC), 2.5 mg (hypertriglyceridemic, low hm ${\gamma}$-PGA, HL), or 5 $mg{\cdot}kg{\cdot}bw^{-1}{\cdot}d^{-1}$ (hypertriglyceridemic, high hm ${\gamma}$-PGA, HH) hm ${\gamma}$-PGA for 4 weeks. The HL and HH groups exhibited significantly lower levels of serum triglyceride, total cholesterol, LDL cholesterol, and free fatty acids than the HC group. The administration of hm ${\gamma}$-PGA reduced serum ALT and AST levels. The activities of lipogenic enzymes such as hepatic malic enzyme and glucose-6-phosphate dehydrogenase as well as glucose-6-phosphate dehydrogenase mRNA expression were significantly decreased by hm ${\gamma}$-PGA administration (p < 0.05). These results indicate that hm ${\gamma}$-PGA has an anti-hypertriglyceridemic effect in high-fructose diet-induced hypertriglyceridemic rats.

• Journal of Microbiology and Biotechnology
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• v.20 no.10
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• pp.1436-1439
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• 2010

Many studies have clarified that poly(${\gamma}$-glutamic acid) (PGA) increases the solubility of $Ca^{2+}$, suggesting that PGA enhances calcium absorption in the small intestine. However, there has been no report on the specific interaction between PGA and $Ca^{2+}$ in water. We studied the aqueous solution properties of PGA calcium salt (PGA-Ca complex). The chelating ability and binding strength of PGA for $Ca^{2+}$ were evaluated. The PGA-Ca complex was soluble in water, in contrast to the insolubility of poly(acrylic acid) (PAA) calcium salt, and the chelating ability of PGA for $Ca^{2+}$ was almost the same as that of PAA. The globular conformation of the PGA-Ca complex in water was estimated by SEC and viscosity measurements. The chelation ability of PGA for $Ca^{2+}$ was examined by $^1H$ NMR. The present study showing the characteristics of the PGA-Ca complex will provide useful information about the calcium absorption by PGA in vivo.