• Journal of the Korean Society of Food Science and Nutrition
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• v.7 no.2
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• pp.21-24
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• 1978

Fermented ordinary Korean soysauce has been one of the most favored seasonings in Korea. The change of free sugars as taste components during the fermentation were analyzed. The results obtained are summarized as follows. 1. Such free sugars as xylose, arabinose, glucose and galactose were detected in Korean ordinary soysauce during the fermentation and galactose was found to be most abundant free sugars. 2. The content of these free sugars in soysauce were increased until 20-40days of fermentation and then decreased rapidly. But slight increase was observed after 80 days of fermentation. 3. It is estimated that galactose plays most important role as sweet taste component in Korean ordinary soysauce.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.5
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• pp.15-23
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• 2010

Bio-ethanol is the most potential next generation automotive fuel for reducing both consumption of crude oil and environmental pollution from renewable resources such as wood, forest residuals, agricultural leftovers and urban wastes. Lignocellulosic based materials can be broken down into individual sugars. Therefore, saccharification is one of the important steps for producing sugars, such as 6-C glucose, galactose, mannose and 5-C xylose, mannose and rhamnose. These sugars can be further broken down and fermented into ethanol. The main objective of this research is to study the feasibility and optimize saccharification and fermentation process for the conversion of lignocellulosic biomass to low cost bioethanol.

• Microbiology and Biotechnology Letters
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• v.51 no.1
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• pp.59-68
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• 2023

Xylanase is an industrially relevant enzyme used for the production of xylobiose and xylose. Various methods are used to enhance the microbial yield of xylanase. In the present study, co-culturing of Bacillus subtilis and Bacillus pumilus were investigated using submerged fermentation for xylanase production, which was markedly increased when sal, sagwan, newspaper, wheat bran, and xylan were used as single carbon sources. Maximum xylanase production was reported after 5 days of incubation in optimized media at pH 7.0 and 37℃, resulting in 2.69 ± 0.25 µmol/min by coculture. The 1:1 ratio of sal and sagwan in optimized production media was shown to be suitable for xylanase synthesis in submerged fermentation (SMF). In comparison to mono-culture using B. pumilus and B. subtilis, co-culturing resulted in an overall 3.8-fold and 2.15-fold increase in xylanase production, respectively.

• Applied Biological Chemistry
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• v.47 no.1
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• pp.85-91
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• 2004

In order to improve foxtail millet wine, a traditional Jeju cereal wine, fermentation characteristics of millet Yakju with different types of Nuruks prepared using isolated Aspergillus sp. and Rhizopus sp. were investigated. When the millet wine was brewed with the Nuruk prepared in this study, the combination ratio of wheat flour: barley : wheat bran : millet = 8 : 1 : 1 : 0 (pellet) showed the highest level of alcohol concentration, and a more favorable score than Kuksundang Nuruk in sensory evaluation. The main organic acids in millet wine were lactic and acetic acids, and the minor organic acids were fumaric, oxalic, citric and malic acids. Analysis of sugar compositions showed that glucose, arabinose, and maltose were present in decreasing order, and that xylose was also detected. Flavor components of millet wine were mainly iso-amyl, iso-butyl and n-propyl alcohols. Ethylacetate and acetadehyde were also detected. The contents of iso-butyl and n-propyl alcohols were higher in the millet wine prepared with Kuksundang Nuruk than those prepared with other Nuruks.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.457-462
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• 2015

Hemicellulosic hydrolysates contain not only sugars but also several kinds of ethanol fermentation inhibitory substances such as carboxylic acids, furans and phenolic compounds. In this work, emulsion liquid membrane (ELM) was chosen as a separation technology to remove the inhibitors. A basic simulated hemicellulosic hydrolysate was composed of xylose as sugar, dilute sulfuric acid solution as solvent, and acetic acid as carboxylic acid, and furfural as furan derivative or p-hydroxybenzoic acid(HBA) as phenolic compound was added to the hydrolysate when necessary. Acetic acid and HBA as weak acid could be selectively removed from the hydrolysates in all the ELM systems considered here, but furfural as aldehyde was quite hard to remove. Also, when HBA was added to the basic simulated hemicellulosic hydrolysate, both of acetic acid and HBA in the feed phase could be selectively removed up to 99% in an ELM system with tributyl phosphate as extractant.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.789-795
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• 2014

Acetic acid is the most abundant and serious ethanol fermentation inhibitor in dilute-acid hemicellulosic hydrolysates. A mixture of xylose, acetic acid and sulfuric acid was chosen as a simulated hemicellulosic hydrolysate so as to find an optimal separation system to selectively remove acetic acid from the hydrolysates. In order to attain the purpose, emulsion liquid membrane was applied to removal of acetic acid from the simulated hemicellulosic hydrolysate. The effects of main constituents of water-in-oil (W/O) emulsion, such as amine extractant type, surfactant composition, additive type, and type and concentration of stripping agent, on extraction of acetic acid, xylose, and sulfuric acid in the simulated hemicellulosic hydrolysate were investigated. Under specific experimental conditions, degree of extraction of acetic acid was higher than 95% while loss of xylose was insignificant, which means that the current emulsion liquid membrane can be an economically feasible process.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.530-535
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• 2019

Diverse types of nuruks (traditional Korean fermentation initiators) were examined in order to isolate thermotolerant yeast strains capable of utilizing xylose as a carbon source. Among twenty yeast strains that grew at 46℃, MBY/L1597 showed a notably higher specific growth rate than other strains. This strain was identified as Millerozyma farinosa. While the control strain M. farinosa KCTC27412 (= CBS7064) did not show xylose reductase (XR) activity and apparent growth at 46℃, M. farinosa MBY/L1597 exhibited XR activity of 4.98 ± 0.49 U/mg protein when NADPH was used as a cofactor. M. farinosa MBY/L1597 cultured at 46℃ produced (9.87 ± 1.00 g/l) xylitol from 20 g/l xylose, corresponding to approximately 50% yield. M. farinosa MBY/L1597 was deposited at the Korean Collection for Type Cultures as KCTC27797.

• Journal of Microbiology and Biotechnology
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• v.29 no.2
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• pp.244-255
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• 2019

Xylose isomerase (XI; E.C. 5.3.1.5) catalyzes the isomerization of xylose to xylulose, which can be used to produce bioethanol through fermentation. Therefore, XI has recently gained attention as a key catalyst in the bioenergy industry. Here, we identified, purified, and characterized a XI (PbXI) from the psychrophilic soil microorganism, Paenibacillus sp. R4. Surprisingly, activity assay results showed that PbXI is not a cold-active enzyme, but displays optimal activity at $60^{\circ}C$. We solved the crystal structure of PbXI at $1.94-{\AA}$ resolution to investigate the origin of its thermostability. The PbXI structure shows a $({\beta}/{\alpha})_8$-barrel fold with tight tetrameric interactions and it has three divalent metal ions (CaI, CaII, and CaIII). Two metal ions (CaI and CaII) located in the active site are known to be involved in the enzymatic reaction. The third metal ion (CaIII), located near the ${\beta}4-{\alpha}6$ loop region, was newly identified and is thought to be important for the stability of PbXI. Compared with previously determined thermostable and mesophilic XI structures, the ${\beta}1-{\alpha}2$ loop structures near the substrate binding pocket of PbXI were remarkably different. Site-directed mutagenesis studies suggested that the flexible ${\beta}1-{\alpha}2$ loop region is essential for PbXI activity. Our findings provide valuable insights that can be applied in protein engineering to generate low-temperature purpose-specific XI enzymes.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1485-1495
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• 2022

The development of a yeast strain capable of fermenting mixed sugars efficiently is crucial for producing biofuels and value-added materials from cellulosic biomass. Previously, a mutant Pichia stipitis YN14 strain capable of co-fermenting xylose and cellobiose was developed through evolutionary engineering of the wild-type P. stipitis CBS6054 strain, which was incapable of co-fermenting xylose and cellobiose. In this study, through genomic and transcriptomic analyses, we sought to investigate the reasons for the improved sugar metabolic performance of the mutant YN14 strain in comparison with the parental CBS6054 strain. Unfortunately, comparative whole-genome sequencing (WGS) showed no mutation in any of the genes involved in the cellobiose metabolism between the two strains. However, comparative RNA sequencing (RNA-seq) revealed that the YN14 strain had 101.2 times and 5.9 times higher expression levels of HXT2.3 and BGL2 genes involved in cellobiose metabolism, and 6.9 times and 75.9 times lower expression levels of COX17 and SOD2.2 genes involved in respiration, respectively, compared with the CBS6054 strain. This may explain how the YN14 strain enhanced cellobiose metabolic performance and shifted the direction of cellobiose metabolic flux from respiration to fermentation in the presence of cellobiose compared with the CBS6054 strain.