• Journal of Microbiology and Biotechnology
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• 제27권4호
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• pp.649-659
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• 2017

Extremophilic microorganisms have established a diversity of molecular strategies in order to survive in extreme conditions. Biocatalysts isolated by these organisms are termed extremozymes, and possess extraordinary properties of salt allowance, thermostability, and cold adaptivity. Extremozymes are very resistant to extreme conditions owing to their great solidity, and they pose new opportunities for biocatalysis and biotransformations, as well as for the development of the economy and new line of research, through their application. Thermophilic proteins, piezophilic proteins, acidophilic proteins, and halophilic proteins have been studied during the last few years. Amylases, proteases, lipases, pullulanases, cellulases, chitinases, xylanases, pectinases, isomerases, esterases, and dehydrogenases have great potential application for biotechnology, such as in agricultural, chemical, biomedical, and biotechnological processes. The study of extremozymes and their main applications have emerged during recent years.

• Journal of Microbiology and Biotechnology
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• 제28권11호
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• pp.1876-1882
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• 2018

A series of pentacyclic triterpenoids similar to glycyrrhetinic acid were designed and synthesized via the combination of chemical modification and microbial catalysis. All products were screened for the glycogen phosphorylases inhibitory activities in vitro. Within this series of derivatives, compound 5 displayed good inhibitory activities with $IC_{50}$ value of $27.7{\mu}M$, which is better than that of the other derivatives and glycyrrhetinic acid. Structure-activity relationship (SAR) analysis of these inhibitors was also discussed.

• Journal of Microbiology and Biotechnology
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• 제29권2호
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• pp.179-190
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• 2019

Bacillus subtilis spore surface display (BSSD) technology is considered to be one of the most promising approaches for expressing heterologous proteins with high activity and stability. Currently, this technology is used for various purposes, such as the production of enzymes, oral vaccines, drugs and multimeric proteins, and the control of environmental pollution. This paper presents an overview of the latest developments in BSSD technology and its application in protein engineering. Finally, the major limitations of this technology and future directions for its research are discussed.

• Journal of Microbiology and Biotechnology
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• 제27권1호
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• pp.92-100
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• 2017

Acetoin (AC) is a volatile platform compound with various potential industrial applications. AC contains two stereoisomeric forms: (3S)-AC and (3R)-AC. Optically pure AC is an important potential intermediate and widely used as a precursor to synthesize novel optically active materials. In this study, chiral (3R)-AC production from meso-2,3-butanediol (meso-2,3-BD) was obtained using recombinant Escherichia coli cells co-expressing meso-2,3-butanediol dehydrogenase (meso-2,3-BDH), NADH oxidase (NOX), and hemoglobin protein (VHB) from Serratia sp. T241, Lactobacillus brevis, and Vitreoscilla, respectively. The new biocatalyst of E. coli/pET-mbdh-nox-vgb was developed and the bioconversion conditions were optimized. Under the optimal conditions, 86.74 g/l of (3R)-AC with the productivity of 3.61 g/l/h and the stereoisomeric purity of 97.89% was achieved from 93.73 g/l meso-2,3-BD using the whole-cell biocatalyst. The yield and productivity were new records for (3R)-AC production. The results exhibit the industrial potential for (3R)-AC production via whole-cell biocatalysis.

• 분석과학
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• 제30권3호
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• pp.138-145
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• 2017

Microwave-assisted organic synthesis has gained a remarkable interest over the past years because of its advantages - (i) rapid energy transfer and superheating, (ii) higher yield and rapid reaction, (iii) cleaner reactions. Ionic liquids are well known for their unique properties such as negligible vapor pressure and high thermal stability. With these properties, ionic liquids have gained increasing attention as green, multi-use reaction media. Recently, ionic liquids have been applied as reaction media for biocatalysis. Lipase-catalyzed reactions in ionic liquids provide high activity and yield compared to conventional organic solvents or solvent free system. Since polar molecules are generally good absorbent to microwave radiation, ionic liquids were investigated as reaction media to improve activity and productivity. In this study, therefore, the effect of microwave irradiation in ionic liquids was investigated on lipase catalyzed reactions such as benzyl acetate synthesis and caffeic acid phenethyl ester synthesis. Comparing to conventional heating, microwave heating showed almost the same final conversion but increased initial reaction rate (3.03 mM/min) compared to 2.11 mM/min in conventional heating at $50^{\circ}C$.

• 생명과학회지
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• 제15권5호
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• pp.772-778
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• 2005

광학활성 에폭사이드는 광학활성 의약품, 기능성 식품 제조용 광학활성 중간체로 사용될 수 있다. 바이오촉매를 이용하여 광학활성 에폭사이드를 제조하는 방법으로는, mono-oxygenase나 peroxidase 등을 이용하여 알켄 기질의 이중결합을 비대칭 에폭시화반응을 통해 제조하는 방법이 있다. Kinetic resolution을 이용하는 방법으로는 epoxide hydrolase를 이용하여 특정 이성질체만을 diol로 가수분해하여 제거시켜 광학활성 에폭사이드를 얻는 방법 등이 있다. 다양한 생물전환 기술, directed evolution 및 site-specific muta-genesis 등을 이용한 광학활성 에폭사이드 제조용 바이오촉매개량 기술 등 효율적인 광학활성 에폭사이드 제조 시스템에 대한 연구 개발도 활발히 진행되고 있어 향후에 상업화가 가능할 것으로 기대된다.

• Journal of Microbiology and Biotechnology
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• 제30권1호
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• pp.146-154
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• 2020

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of k_cat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

• Journal of Microbiology and Biotechnology
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• 제17권7호
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• pp.1083-1089
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• 2007

Because of their selectivity and catalytic efficiency, BVMOs are highly valuable biocatalysts for the chemoenzymatic synthesis of a broad range of useful compounds. In this study, we investigated the microbial Baeyer-Villiger oxidation and sulfoxidation of thioanisole and bicyclo[3.2.0]hept-2-en-6-one using whole Escherichia coli cells that recombined with each of the Baeyer-Villiger monooxygenases originated from Pseudomonas aeruginosa PAOl and two from Streptomyces coelicolor A3(2). The three BVMOs were identified in the microbial genome database by a recently described protein sequence motif; e.g., BVMO motif(FXGXXXHXXXW). The reaction products were identified as (R)-/(S)-sulfoxide and 2-oxabicyclo/3-oxabicyclo[3.3.0]oct-6-en-2-one by GC-MS analysis. Consequently, this study demonstrated that the three enzymes can indeed catalyze the Baeyer-Villiger reaction as a biocatalyst, and effective annotation tools can be efficiently exploited as a source of novel BVMOs.

• Journal of Microbiology and Biotechnology
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• 제23권2호
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• pp.195-204
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• 2013

While structured packing modules are known to be efficient for surface wetting and gas-liquid exchange in abiotic surface catalysis, this model study explores structured packing as a growth surface for catalytic biofilms. Microbial biofilms have been proposed as selfimmobilized and self-regenerating catalysts for the production of chemicals. A concern is that the complex and dynamic nature of biofilms may cause fluctuations in their catalytic performance over time or may affect process reproducibility. An aerated continuous trickle-bed biofilm reactor system was designed with a 3 L structured packing, liquid recycling and pH control. Pseudomonas diminuta established a biofilm on the stainless steel structured packing with a specific surface area of 500 $m^2m^{-3}$ and catalyzed the oxidation of ethylene glycol to glycolic acid for over two months of continuous operation. A steady-state productivity of up to 1.6 $gl^{-1}h^{-1}$ was achieved at a dilution rate of 0.33 $h^{-1}$. Process reproducibility between three independent runs was excellent, despite process interruptions and activity variations in cultures grown from biofilm effluent cells. The results demonstrate the robustness of a catalytic biofilm on structured packing, despite its dynamic nature. Implementation is recommended for whole-cell processes that require efficient gas-liquid exchange, catalyst retention for continuous operation, or improved catalyst stability.

• 대한화학회지
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• 제63권4호
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• pp.260-265
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• 2019

Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was selected as the enzyme which will be immobilized on ultrafiltration membrane by fouling with different transmembrane pressure of 1, 2 and 3 bars. ADH will catalyze formaldehyde (CHOH) to methanol ($CH_3OH$) and simultaneously oxidized nicotinamide adenine dinucleotide (NADH) to $NAD^+$. The concentration of enzyme and pH are fixed at 0.1 mg/ml and pH 7.0 respectively. The objective of the study focuses on the effect of different transmembrane pressure (TMP) on enzyme immobilization in term of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that at 1 bar holds the lowest enzyme loading which is 1.085 mg while 2 bar holds the highest enzyme loading which is 1.357 mg out of 3.0 mg as the initial enzyme feed. The permeate flux for each TMP decreased with increasing cumulative permeate volume. The observed rejection is linearly correlated with the TMP where increase in TMP will cause a higher observed rejection. Hermia model predicted that at irreversible fouling with standard blocking dominates at TMP of 3 bar, while cake layer and intermediate blocking dominates at 1 and 2 bar respectively.