• 미생물학회지
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• 제55권1호
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• pp.9-16
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• 2019

다양한 미생물은 세포와 주변의 과산화를 방지하고 여분의 에너지를 보관하기 위해 ${\alpha}$-acetolactate decarboxylase(ALDC)를 이용해 아세토인을 생성한다. 아세토인은 안전한 식품 향미 개선제이기 때문에 ALDC를 이용한 아세토인 생합성에 많은 산업체가 관심을 가지고 있다. ALDC는 ${\alpha}$-acetolactate의 탈카르복실화 반응을 통해 아세토인을 생산하는 금속 의존 효소이다. 본 논문에서는 고초균 아종 spizizenii의 ALDC(bssALDC) 결정구조를 $1.7{\AA}$ 해상도에서 보고한다. bssALDC는 두 개의 ${\beta}$-sheet가 중앙부를 형성하는 ${\alpha}/{\beta}$ 구조를 가진다. bssALDC는 중앙부의 소수성 상호작용과 주변부의 친수성 상호작용을 통해 이합체를 형성한다. bssALDC는 세 개의 histidine 잔기와 세 개의 물 분자를 이용해 아연 이온에 배위결합한다. 구조와 서열의 비교 분석에 기초하여 아연 이온과 이 주변부 bssALDC 잔기들이 bssALDC의 효소 활성부위임을 제안한다.

• Journal of Microbiology and Biotechnology
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• 제22권9호
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• pp.1258-1263
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• 2012

2,3-Butanediol (2,3-BD) is a major metabolite produced by Klebsiella pneumoniae KCTC2242, which is a important chemical with wide applications. Three genes important for 2,3-BD biosynthesis acetolactate decarboxylase (budA), acetolactate synthase (budB), and alcohol dehydrogenase (budC) were identified in K. pneumoniae genomic DNA. With the goal of enhancing 2,3-BD production, these genes were cloned into pUC18K expression vectors containing the lacZ promoter and the kanamycin resistance gene to generate plasmids pSB1-7. The plasmids were then introduced into K. pneumoniae using electroporation. All strains were incubated in flask experiments and 2,3-BD production was increased by 60% in recombinant bacteria harboring pSB04 (budA and budB genes), compared with the parental strain K. pneumoniae KCTC2242. The maximum 2,3-BD production level achieved through fed-batch fermentation with K. pneumoniae SGJSB04 was 101.53 g/l over 40 h with a productivity of 2.54 g/l.h. These results suggest that overexpression of 2,3-BD synthesis-related genes can enhance 2,3-BD production in K. pneumoniae by fermentation.

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.596-606
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• 2019

N-acyl-homoserine lactone quorum sensing (AHL-QS) has been shown to regulate many physiological behaviors in Serratia marcescens MG1. In the current study, the effects of AHL-QS on the biosynthesis of acid and neutral products by S. marcescens MG1 and its isogenic ${\Delta}swrI$ with or without supplementing exogenous N-hexanoyl-L-homoserine lactone ($C_6-HSL$) were systematically investigated. The results showed that swrI disruption resulted in rapid pH drops from 7.0 to 4.8, which could be restored to wild type by supplementing $C_6-HSL$. Furthermore, fermentation product analysis indicated that ${\Delta}swrI$ could lead to obvious accumulation for acidogenesis products such as lactic acid and succinic acid, especially excess acetic acid (2.27 g/l) produced at the early stage of fermentation, whereas solventogenesis products by ${\Delta}swrI$ appeared to noticeably decrease by an approximate 30% for acetoin during 32-48 h and by an approximate 20% for 2,3-butanediol during 24-40 h, when compared to those by wild type. Interestingly, the excess acetic acid produced could be removed in an AHL-QS-independent manner. Subsequently, quantitative real-time PCR was used to determine the mRNA expression levels of genes responsible for acidogenesis and solventogenesis and showed consistent results with those of product synthesis. Finally, by close examination of promoter regions of the analyzed genes, four putative luxI box-like motifs were found upstream of genes encoding acetyl-CoA synthase, lactate dehydrogenase, ${\alpha}$-acetolactate decarboxylase, and Lys-like regulator. The information from this study provides a novel insight into the roles played by AHL-QS in switching from acidogenesis to solventogenesis in S. marcescens MG1.