• Food Science and Biotechnology
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• 제17권5호
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• pp.904-911
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• 2008

Covalent cross-links between a number of proteins and peptides explain why transglutaminase may be widely used by food processing industries. The objective of this work was optimization of the fermentation process to produce transglutaminase from a new microbial source, the Streptomyces sp. P20. The strategy adopted to modify the usual literature media was: (1) fractional factorial design (FFD) to elucidate the key medium ingredients, (2) central composite design (CCD) to optimise the concentration of the key components. Optimization of the medium resulted in not only an 86% increase in microbial transglutaminase activity as compared to the media cited in the literature, but also a reduction in the production cost. Optimal fermentation conditions - namely temperature and agitation rate - were also studied, using CCD methodology. Usual conditions of $30^{\circ}C$ and 100 rpm were within the optimal area. All other parameters for enzyme production were experimentally proven to be optimum fermentation conditions.

• 식물병연구
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• 제27권4호
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• pp.155-163
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• 2021

Dried red peppers are frequently contaminated with mycotoxins during storage. To determine the effect of storage environments on fungal occurrence and subsequent mycotoxin accumulation in dried red peppers, we monitored red pepper powder and whole fruit samples for fungal occurrence under various temperatures and relative humidity (RH) conditions during 340 days. Fungal occurrences fluctuated in both pepper forms throughout the storage but they were higher in pepper powder than whole one, higher under low temperatures (-20℃, 0℃, or 4℃) than others (10℃, 25℃, or 30℃), and higher under RH 93% than RH 51% and 69% in both peppers. The samples exhibiting high fungal occurrences were associated mainly with dominant species such as Aspergillussydowii, Penicillium solitum, P. roqueforti, P. polonicum, or P. chrysogenum. Mycotoxigenic species, including A. flavus, A. ochraceus, A. westerdijkiae, A. tubingensis, and P. citrinum, were also detected throughout the samples. Although mycotoxins were not detected in the samples, mycotoxigenic potential of A. flavus, A. ochraceus, and A. westerdijkiae isolates were confirmed. These results show that low temperatures (-20℃, 0℃, or 4℃) and/or high surrounding RH (>93%) are not safe environments for storage of dried red peppers as fungal growth can occur under these conditions.

• 한국식품저장유통학회지
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• 제30권2호
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• pp.287-299
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• 2023

효소 및 미생물 복합제를 사용하여 인비트로 발효 루왁커피를 제조하여 non-fermented coffee beans(NFC)과 fermented coffee beans(FC)의 커피 품질을 비교하였다. 총유리아미노산 함량은 NFC가 254.01±4.89 mg/mL, FC가 264.15±16.80 mg/mL로 FC의 함량이 다소 높은 것으로 확인되었다. 이때 NFC는 glutamic acid, γ-aminon-butyric acid 등이 높았으나, FC는 lysine, leucine, valine 등 필수아미노산의 함량이 높았다. 커피 생두의 발효과정은 sucrose의 감소와 fructose 및 glucose의 유의적인 증가를 가져왔다. 커피 추출물의 색도는 NFC에 비해 FC 시료에서 높은 명도(L)와 적색도(a) 및 황색도(b)를 보였다. 카페인 함량은 NFC 1,130.22±1.55 ㎍/mL, FC 696.94±0.04 ㎍/mL로써 발효 후 약 38%의 카페인이 감소되었다. 폴리페놀 및 클로로겐산 함량은 NFC에서 각각 2.31±0.01 mg GAE/mL와 531.81±27.32 ㎍/mL, FC에서 각각 2.03±0.07 mg GAE/mL와 264.46±2.47 ㎍/mL로 발효에 따라 떫은맛 관련 성분의 함량이 유의적으로 감소됨을 알 수 있었다. 전자코 분석에서 NFC와 FC의 휘발성 향성분의 차이가 뚜렷함이 확인되었고, methylethyl formate, 2-methyl-1, 3-cyclopentadiene, 2-chloro-2-methylbutane, 2-methylbutanal 등의 휘발성 화합물이 발효 후 높은 강도로 감지되었다. 관능 평가에서는 NFC 추출물보다 FC 추출물의 aroma, body, aftertaste, overall에서 높은 관능 평점을 보여주었다(p<0.001). 이상의 결과에서 효소 및 미생물 복합제를 사용한 커피 생두의 발효는 유효 성분들의 변화를 일으켜 커피 원두의 로스팅 과정 중 Maillard 반응을 촉진함으로써, 향미가 증가되고 카페인 함량이 감소된 인비트로 루왁 커피의 제조 가능성을 시사하였다.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1547-1556
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• 2009

A novel thermostable $\alpha$-glucosidase (TtGluA) from Thermoanaerobacter tengcongensis MB4 was successfully expressed in E. coli and characterized. The TtgluA gene contained 2,253 bp, which encodes 750 amino acids. The native TtGluA was a trimer with monomer molecular mass of 89 kDa shown by SDS-PAGE. The purified recombinant enzyme showed hydrolytic activity on maltooligosaccharides, p-nitrophenyl-$\alpha$-D-glucopyranide, and dextrin with an exotype cleavage manner. TtGluA showed preference for short-chain maltooligosaccharides and the highest specific activity for maltose of 3.26 units/mg. Maximal activity was observed at $60^{\circ}C$ and pH 5.5. The half-life was 2 h at $60^{\circ}C$. The enzyme showed good tolerance to urea and SDS but was inhibited by Tris. When maltose with the concentration over 50 mM was used as substrate, TtGluA was also capable of catalyzing transglycosylation to produce $\alpha$-1,4-linked maltotriose and $\alpha$-1,6-linked isomaltooligosaccharides. More importantly, TtGluA showed exclusive regiospecificity with high yield to produce $\alpha$-1,6-linked isomaltooligosaccharides when the reaction time extended to more than 10 h.

• Journal of Microbiology and Biotechnology
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• 제20권2호
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• pp.254-264
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• 2010

To obtain an efficient natural lignocellulolytic complex enzyme, we screened an efficient lignocellulose-degrading composite microbial system (XDC-2) from composted agricultural and animal wastes amended soil following a long-term directed acclimation. Not only could the XDC-2 degrade natural lignocelluloses, but it could also secrete extracellular xylanase efficiently in liquid culture under static conditions at room temperature. The XDC-2 degraded rice straw by 60.3% after fermentation for 15 days. Hemicelluloses were decomposed effectively, whereas the extracellular xylanase activity was dominant with an activity of 8.357 U/ml on day 6 of the fermentation period. The extracellular crude enzyme noticeably hydrolyzed natural lignocelluloses. The optimum temperature and pH for the xylanase activity were $40^{\circ}C$ and 6.0. However, the xylanase was activated in a wide pH range of 3.0-10.0, and retained more than 80% of its activity at $25-35^{\circ}C$ and pH 5.0-8.0 after three days of incubation in liquid culture under static conditions. PCR-DGGE analysis of successive subcultures indicated that the XDC-2 was structurally stable over long-term restricted and directed cultivation. Analysis of the 168 rRNA gene clone library showed that the XDC-2 was mainly composed of mesophilic bacteria related to the genera Clostridium, Bacteroides, Alcaligenes, Pseudomonas, etc. Our results offer a new approach to exploring efficient lignocellulolytic enzymes by constructing a high-performance composite microbial system with synergistic complex enzymes.

• Journal of Microbiology and Biotechnology
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• 제11권2호
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• pp.342-345
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• 2001

A bacterial strain PH-4, which produces an enzyme catalyzing the degradation of crosslinked poly(${\gamma}$-glutamic acid) hydrogels, was isolated and identified as a Flavobacterium sp. The enzyme was obtained by the sonication of the bacterial cells preincubated in a Bouillon medium with shaking, without adding of poly(${\gamma}$-glutamic acid) as an inducer. The products of the hydrogel degraded by the crude enzyme agreed closely with the depolymerized materials in SDS-polyacrylamide gel electrophoresis using methylene blue staining, and with a glutamic acid monomer on thin-layer chromatography, thereby suggesting that strain PH-4 produced a kind of exohydrolase.

• 한국식품영양학회지
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• 제13권2호
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• pp.176-180
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• 2000

Microbial protease has been interesting due to the biological roles in the producing microorganism. A thermophilic Actinomyces produing protease was isolated from soil. The optimal medium composition and culture conditions for maximum protease production was as follows 0.5% soluble starch, 0.5% yeast extract. 0.1% K2HPO4, 0.05% CaCl2, initial pH 8.0 at 50$^{\circ}C$ for 48hours. The protease was purified by the procedure of ammonium sulfate precipitation, anion exchange chromatography(LC), DEAE high performance liquid chromatography and GPC HPLC. The purification fold of the purified enzyme was increased about 22.6. The optimal pH and temperature for reaction of the purified enzyme were 7.5 and 60$^{\circ}C$. The purified enzyme was stable for the pH range from 6.0 to 8.5, but was unstable when treated at 80$^{\circ}C$ for 10 minutes. The activity of the enzyme was inhibited by Ag+ and Cu2+.

• Preventive Nutrition and Food Science
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• 제3권2호
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• pp.128-132
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• 1998

7S globulin has been isolate from the defatted soybean meal(glycine max,. merill) by Sepharose-6B column chromatography and CM-Sephadex column chromatography. Coagulum of 7S globulin formed at a temperature of $65^{\circ}C$ in microbial enzyme treatment. In order to characterize the structure of the coagulum, three kinds of coagulum (enzyme-, calcium-and acid-induced coagulum)were compared througth the Scanning Electron Microscope(SEM). The network structure was found to be of two levels. First, there was an appearance on the molecular level in the form of strands. Second, there was a denser network with a fine structure.

• Journal of Microbiology and Biotechnology
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• 제25권6호
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• pp.887-892
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• 2015

Uricase is an important microbial enzyme that can be used in the clinical treatment of gout, hyperuricemia, and tumor lysis syndrome. A total of 127 clinical isolates of Pseudomonas aeruginosa were tested for uricase production. A Pseudomonas strain named Ps43 showed the highest level of native uricase enzyme expression. The open reading frame of the uricase enzyme was amplified from Ps43 and cloned into the expression vector pRSET-B. Uricase was expressed using E. coli BL21 (DE3). The ORF was sequenced and assigned GenBank Accession No. KJ718888. The nucleotide sequence analysis was identical to the coding sequence of uricase gene puuDof P. aeruginosa PAO1. We report the successful expression of P. aeruginosa uricase in Escherichia coli. E. coli showed an induced protein with a molecular mass of about 58 kDa that was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. We also established efficient protein purification using the Ni-Sepharose column with activity of the purified enzyme of 2.16 IU and a 2-fold increase in the specific activity of the pure enzyme compared with the crude enzyme.

• 미생물학회지
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• 제39권4호
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• pp.230-234
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• 2003

Bacillus amyloliquefaciens psychrotrophic strain이 분비하는 세포 외 단백질 가수분해효소를 정제하여, endopeptidase 활성에 관한 특성을 분석하였다. Protease SE910로 명명된 효소는 단백질 내부의 leucine에 연결된 peptide 결합만을 가수분해하는 endopeptidase로 작용한다. 효소를 특이한 아미노산 잔기에 작용하는 화학수식제와 반응하였을 때 효소의 활성부위에 관여하는 아미노산 잔기가 수식되었을 때는 효소활성이 저해를 받는다. 본 효소는 serine을 수식하는 PMSF에의해 endopeptidase 활성이 완전히 저해되었으며, 카르복실 기능기를 수식하는 화학수식제에 의해 저해되었고, lysine을 화학수식하는 PLP에 의해서는 큰 영향을 받지 않았다. 이것은 본 효소의 endopeptidase 활성에 serine과 aspartic acid 잔기가 관여하는 것을 의미한다. 구조적으로 leucine을 포함하는 유도체인 bestatin은 효소의 endopeptidase 활성을 경쟁적으로 저해하였다.