• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.763-766
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• 2010

An efficient and simple fermentation process was developed for the production of ${\gamma}$-aminobutyric acid (GABA) by Lactobacillus sakei B2-16. When the L. sakei B2-16 was cultivated in the rice bran extracts medium containing 4% sucrose, 1% yeast extract, and 12% monosodium glutamate, the maximum GABA concentration reached 660.0 mM with 100% conversion yield, showing the 2.4- fold higher GABA concentration compared with the modified MRS medium without the rice bran extracts. The GABA production was scaled-up from a laboratory scale (5 l) to a pilot (300 l) and a plant (5,000 l) scale to investigate the application possibility of GABA production to industrial fields. The production yields at the pilot and plant scales were similar to the laboratory scale using rice bran extracts medium, which could be effective for the low-cost production of GABA.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.363-366
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• 2004

In order to obtain an industrial strain with higher L(+)-lactic acid yield, the wild type strain Rhizopus oryzae PW352 was mutated by means of Nitrogen ions implantation (l5 Kev, $7.8 \times 10^{14} - 2.08 \times 10^{15} ions/Cm^2$ and two mutants RE3303 and RF9052 were isolated. After 36 h shake-flask cultivation, the concentration of L(+)-lactic acid reached 131-136 g/l, the conversion rate of glucose was as high as 86%-90% and the productivity was 3.61 g/l.h. It was almost a 75% increase in lactic acid production compared with the wild type strain. Maximum fermentation temperature of RF9052 was increased to $45^{\circ}C$ from original $36^{\circ}C$. At the same time, the preferred range of fermentation temperature of RF9052 was broadened compared with PW352.

• KSBB Journal
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• v.27 no.3
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• pp.137-144
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• 2012

Among various pretreatment processes for bioethanol production, extrusion pretreatment, one of cheap and simple process was investigated to efficiently produce fermentable sugars from micro alga, Chlorella sp. The biomass was pretreated in a single screw extruder at five different barrel temperatures of 45, 50, 55, 60 and $65^{\circ}C$, respectively with five screw rotation speed of 10, 50, 100, 150 and 200 rpm. The pretreated biomass was reacted with two different hydrolyzing enzymes of cellulase and amyloglucosidase since the biomass contained different types of carbohydrates, compared to cellulose of agricultural by-products such wheat and corn stovers, etc. In general, higher glucose conversion yield was obtained as 13.24 (%, w/w) at $55^{\circ}C$ of barrel temperature and 100 rpm of screw speed conditions. In treating 5 FPU/glucan of cellulase and 150 Unit/mL of amyloglucosidase, ca. 64% of cellulose and 40% of polysaccharides in the micro alga were converted into glucose, which was higher yields than those from other reported data without applying an extrusion process. 84% of the fermentable sugars obtained from the hyrolyzing processes were fermented into ethanol in considering 50% of theoretical maximum fermentation yield of the yeast. These results implied that high speed extrusion could be suitable as a pretreatment process for the production of bioethanol from Chlorella sp.

• Microbiology and Biotechnology Letters
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• v.51 no.3
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• pp.257-267
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• 2023

The potential polyhydroxyalkanoates (PHA)-producing bacteria, Bacillus megaterium PP-10, was successfully isolated and studied its feasibility for utilization of pineapple peel waste (PPW) as a cheap carbon substrate. The PPW was pretreated with 1% (v/v) H₂SO₄ under steam sterilization and about 26.4 g/l of total reducing sugar (TRS) in pineapple peel hydrolysate (PPH) was generated and main fermentable sugars were glucose and fructose. A maximum cell growth and PHA concentration of 3.63 ± 0.07 g/l and 1.98 ± 0.09 g/l (about 54.58 ± 2.39%DCW) were received in only 12 h when grown in PPH. Interestingly, PHA productivity and biomass yield (Y_x/s) in PPH was about 4 times and 1.5 times higher than in glucose. To achieve the highest DCW and PHA production, the optimal culture conditions e.g. carbon to nitrogen ratios of 40 mole/mole, incubation temperature at 35℃ and shaking speed of 200 rpm were performed and a maximum DCW up to 4.24 ± 0.04 g/l and PHA concentration of 2.68 ± 0.02 g/l (61% DCW) were obtained. The produced PHA was further examined its monomer composition and found to contain only 3-hydroxybutyrate (3HB). This finding corresponded with the presence of class IV PHA synthase gene. Finally, certain thermal properties of the produced PHA i.e. the melting temperature (T_m) and the glass transition temperature (T_g) were about 176℃ and -4℃, respectively whereas the M_w was about 1.07 KDa ; therefore, the newly isolated B. megaterium PP-10 is a promising bacterial candidate for the efficient conversion of low-cost PPH to PHA.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• KSBB Journal
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• v.9 no.5
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• pp.518-524
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• 1994

Serum free medium was developed to cultivate Human Embryonic Kidney cells with Cytodex III microcarriers. The cells normally attached and spreaded on the microcarriers in serum free medium, and grew well by bead to bead processes. 85% of attachment yield was obtained on Cytodex III in this medium, compared to about 93% in 1% serum containing medium. About 90% of the attached HEK cells spreaded after 6 hours of post-attachment periods on the surface of microcarrier. Maximum cell density and scu-PA concentration in a serum free medium were $9.1{\times}10^5$ cells/ml and 1790 IU/ml, respectively, with fed-batch cultivation. Maximum cell density and scu-PA concentration in this medium with perfusion cultivation were $2.5{\times}10^6$ cells/ml and 1820 IU/ml, respectively. The conversion of single chain urokinase type plasminogen activator (scu-PA) into two chain type plasminogen activator (tc-PA) was less than 5% in a serum free medium compared to about 10% in 0.5% serum containing medium.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.1
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• pp.97-104
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• 2013

Methyl alcohol is one of the basic intermediates in the chemical industry and is also being used as a fuel additive and as a clean burning fuel. In this study, conversion of carbon dioxide to methyl alcohol was investigated using catalytic chemical methods. Ceramic monoliths (M) with $400cell/in^2$ were used as catalyst supports. Monolith-supported CuO-ZnO catalysts were prepared by wash-coat method. The prepared catalysts were characterized by using ICP analysis, TEM images and XRD patterns. The catalytic activity for carbon dioxide hydrogenation to methyl alcohol was investigated using a flow-type reactor under various reaction temperature, pressure and contact time. In the preparation of monolith-supported CuO-ZnO catalysts by wash-coat method, proper concentration of precursors solution was 25.7% (w/v). The mixed crystal of CuO and ZnO was well supported on monolith. And it was known that more CuO component may be supported than ZnO component. Conversion of carbon dioxide was increased with increasing reaction temperature, but methyl alcohol selectivity was decreased. Optimum reaction temperature was about $250^{\circ}C$ under 20 atm because of the reverse water gas shift reaction. Maximum yield of methyl alcohol over CuO-ZnO/M catalyst was 5.1 mol% at $250^{\circ}C$ and 20 atm.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.344-354
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• 2015

To investigate the effects of ionic liquid pretreatment on biomass, giant miscanthus was treated with 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) and 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) at three temperature conditions ($90^{\circ}C$, $110^{\circ}C$, and $130^{\circ}C$). As temperature condition increased, yield of the cellulose-rich product (CP) was reduced from 87.2% to 67.6%, while yield of the ionic liquid lignin (ILL) increased from 2.2% to 9.9%. Compared to the ILL, CP had lower carbon contents and higher oxygen contents. Enzymatic hydrolysis of CPs showed that conversion ratio of CP treated with [Emim][OAc] at $110^{\circ}C$ was 56.7%, the highest digestibility. Thermogravimetric analysis indicated that the maximum degradation rate decreased as temperature condition increased. In addition, maximum degradation temperature of ILL treated with [Emim][OAc] ranged from 274 to $279^{\circ}C$ which was lower than that of ILL treated with [Bmim][OAc]. Analytical date for ${\beta}$-O-4 linkage frequency in the ILL revealed that ${\beta}$-O-4 linkage frequency in the ILL decreased as the temperature rose. Furthermore, the highest S/G ratio of the ILL was determined to ca. 1.2 obtained from [Bmim][OAc] treatment at $110^{\circ}C$.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.45-51
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• 2014

This is to study the effects of various pretreatment methods of agricultural residue, corn stover, and to compare the feature and pros and cons of each method including dilute sulfuric acid (DSA), soaking in aqueous ammonia (SAA), and ammonia recycle percolation (ARP). In order to convert corn stover to ethanol, various pretreatments followed by simultaneous saccharification and co-fermentation (SSCF) were tested and evaluated in terms of ethanol yield. With 3%, w/w of glucan loading using ARP-, DSA-, and SAA-treated solids, SSCFs using recombinant E. coli strain (ATCC$^{(R)}$ 55124) with commercial enzymes (15 FPU of Spezyme CP/g-glucan and 30 CBU/g-glucan enzyme loading) were tested. In the SSCF tests, 87, 90, and 78% of theoretical maximum ethanol yield were observed using ARP-, DSA-, and SAA-treated solids, respectively, which were 69, 58, and 74% on the basis of total carbohydrates (glucan + xylan) in the untreated corn stover. Ethanol yield of SAA-treated solid was higher than those of ARP- and DSA-treated solids. In addition, SSCF test using treated solids plus pretreated hydrolysate indicated that the DSA-treated hydrolysate showed the strongest inhibition effect on the KO11 strain, whereas the ARP-treated hydrolysate was found to have the second strongest inhibition effect. Bioconversion scheme using SAA pretreatment and SSCF can make the downstream process simple, which is suggested to produce ethanol economically because utilization of hemicellulose in the hydrolysate is not necessary.

• Journal of Microbiology and Biotechnology
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• v.33 no.11
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• pp.1521-1530
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• 2023

An α-L-rhamnosidase gene from Thermoclostridium. stercorarium subsp. thermolacticum DSM 2910 (TstRhaA) was cloned and expressed. The maximum TstRhaA activity of the protein reached 25.2 U/ml, and the molecular mass was approximately 106.6 kDa. The protein was purified 8.0-fold by Ni-TED affinity with an overall recovery of 16.6% and a specific activity of 187.9 U/mg. TstRhaA activity was the highest at 65℃ and pH 6.5. In addition, it exhibited excellent thermal stability, better pH stability, good tolerance to low concentrations of organic reagents, and high catalytic activity for p-nitrophenyl-α-L-rhamnopyranoside (pNPR). Substrate specificity studies showed that TstRhaA exhibited a high specific activity for rutin. At 60℃, pH 6.5, and 0.3 U/ml enzyme dosage, 60 g/l rutin was converted to 45.55 g/l isoquercitrin within 150 min. The molar conversion rate of rutin and the yield of isoquercitrin were 99.8% and 12.22 g/l/h, respectively. The results suggested that TstRhaA could be used for mass production of isoquercitrin.