http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Lee, Tae-Hee,Kim, Myoung-Dong,Shin, So-Yeon,Lim, Hyung-Kweon,Seo, Jin-Ho Elsevier 2006 Journal of biotechnology Vol.126 No.4
<P><B>Abstract</B></P><P>The <I>GAL1</I> gene encoding galactokinase was disrupted in a recombinant <I>Saccharomyces cerevisiae</I> strain in which production of LK8 protein, a kringle fragment of human apolipoprotein, is under the control of <I>GAL1</I> promoter. Null mutation of the <I>HXK2</I> gene was introduced further in the <I>gal1Δ</I> strain to relieve glucose repression. A pattern for LK8 expression was compared for the two recombinant <I>S. cerevisiae</I> systems in continuous and fed-batch cultivations. A critical dilution rate in continuous cultivation that repressed LK8 expression was significantly higher for the <I>gal1Δhxk2Δ</I> strain than that for the <I>gal1Δ</I> strain to sustain the LK8 production even at high glucose consumption rate. Expressed LK8 for the <I>gal1Δ</I> strain was not detectable when the dilution rate exceeded 0.05h<SUP>−1</SUP>. Maximum LK8 concentration of 57mgl<SUP>−1</SUP> was obtained in glucose-limited fed-batch cultivation of the <I>gal1Δhxk2Δ</I> strain, corresponding to a 13.8-fold enhancement compared with the <I>gal1Δ</I> strain grown under the same conditions.</P>
Jeon, Woo Young,Yoon, Byoung Hoon,Ko, Byoung Sam,Shim, Woo Yong,Kim, Jung Hoe Springer-Verlag 2012 Bioprocess and biosystems engineering Vol.35 No.1
<P>Xylose reductase (XR) is the first enzyme in <SMALL>D</SMALL>-xylose metabolism, catalyzing the reduction of <SMALL>D</SMALL>-xylose to xylitol. Formation of XR in the yeast <I>Candida tropicalis</I> is significantly repressed in cells grown on medium that contains glucose as carbon and energy source, because of the repressive effect of glucose. This is one reason why glucose is not a suitable co-substrate for cell growth in industrial xylitol production. XR from the ascomycete <I>Neurospora crassa</I> (NcXR) has high catalytic efficiency; however, NcXR is not expressed in <I>C</I>. <I>tropicalis</I> because of difference in codon usage between the two species. In this study, NcXR codons were changed to those preferred in <I>C</I>. <I>tropicalis</I>. This codon-optimized NcXR gene (termed NXRG) was placed under control of a constitutive glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter derived from <I>C</I>. <I>tropicalis</I>, and integrated into the genome of xylitol dehydrogenase gene (<I>XYL2</I>)-disrupted <I>C</I>. <I>tropicalis</I>. High expression level of NXRG was confirmed by determining XR activity in cells grown on glucose medium. The resulting recombinant strain, LNG2, showed high XR activity (2.86 U (mg of protein)<SUP>−1</SUP>), whereas parent strain BSXDH-3 showed no activity. In xylitol fermentation using glucose as a co-substrate with xylose, LNG2 showed xylitol production rate 1.44 g L<SUP>−1</SUP> h<SUP>−1</SUP> and xylitol yield of 96% at 44 h, which were 73 and 62%, respectively, higher than corresponding values for BSXDH-3 (rate 0.83 g L<SUP>−1</SUP> h<SUP>−1</SUP>; yield 59%).</P>
Lee, Ki‐,Sung,Hong, Min‐,Eui,Jung, Suk‐,Chae,Ha, Suk‐,Jin,Yu, Byung Jo,Koo, Hyun Min,Park, Sung Min,Seo, Jin‐,Ho,Kweon, Dae‐,Hyuk,Park, Jae Chan,Jin, Yong‐,Su Wiley Subscription Services, Inc., A Wiley Company 2011 Biotechnology and Bioengineering Vol.108 No.3
<P><B>Abstract</B></P><P>Although <I>Saccharomyces cerevisiae</I> is capable of fermenting galactose into ethanol, ethanol yield and productivity from galactose are significantly lower than those from glucose. An inverse metabolic engineering approach was undertaken to improve ethanol yield and productivity from galactose in <I>S</I>. <I>cerevisiae</I>. A genome‐wide perturbation library was introduced into <I>S</I>. <I>cerevisiae</I>, and then fast galactose‐fermenting transformants were screened using three different enrichment methods. The characterization of genetic perturbations in the isolated transformants revealed three target genes whose overexpression elicited enhanced galactose utilization. One confirmatory (<I>SEC53</I> coding for phosphomannomutase) and two novel targets (<I>SNR84</I> coding for a small nuclear RNA and a truncated form of <I>TUP1</I> coding for a general repressor of transcription) were identified as overexpression targets that potentially improve galactose fermentation. Beneficial effects of overexpression of <I>SEC53</I> may be similar to the mechanisms exerted by overexpression of <I>PGM2</I> coding for phosphoglucomutase. While the mechanism is largely unknown, overexpression of <I>SNR84</I>, improved both growth and ethanol production from galactose. The most remarkable improvement of galactose fermentation was achieved by overexpression of the truncated <I>TUP1</I> (t<I>TUP1</I>) gene, resulting in unrivalled galactose fermentation capability, that is 250% higher in both galactose consumption rate and ethanol productivity compared to the control strain. Moreover, the overexpression of t<I>TUP1</I> significantly shortened lag periods that occurs when substrate is changed from glucose to galactose. Based on these results we proposed a hypothesis that the mutant Tup1 without C‐terminal repression domain might bring in earlier and higher expression of <I>GAL</I> genes through partial alleviation of glucose repression. mRNA levels of <I>GAL</I> genes (<I>GAL1</I>, <I>GAL4</I>, and <I>GAL80</I>) indeed increased upon overexpression of <I>tTUP</I>. The results presented in this study illustrate that alteration of global regulatory networks through overexpression of the identified targets (<I>SNR84</I> and t<I>TUP1</I>) is as effective as overexpression of a rate limiting metabolic gene (<I>PGM2</I>) in the galactose assimilation pathway for efficient galactose fermentation in <I>S</I>. <I>cerevisiae</I>. In addition, these results will be industrially useful in the biofuels area as galactose is one of the abundant sugars in marine plant biomass such as red seaweed as well as cheese whey and molasses. Biotechnol. Bioeng. 2011; 108:621–631. © 2010 Wiley Periodicals, Inc.</P>
Oh, B.R.,Hong, W.K.,Heo, S.Y.,Luo, L.H.,Kondo, A.,Seo, J.W.,Kim, C.H. Elsevier Applied Science 2013 Bioresource technology Vol.130 No.-
In the present study, mutant strain of Klebsiella pneumoniae with deletion of the crr gene encoding EIIA<SUP>Glc</SUP> (a component of the glucose-specific phosphoenolpyruvate-dependent transferase system [PTS]) was prepared. This eliminated the ability of the strain to mediate carbon catabolite repression (CCR). Production of 1,3-propanediol (1,3-PD) from glycerol by the crr mutant strain was enhanced (compared to that of the parent) in the presence of glucose. Using molasses as a co-substrate of glycerol, the maximum yield of 1,3-PD was 60.4% greater (81.2g/l) than that obtained when glycerol was used alone, under optimum fermentation conditions.
Seong Hyeon Jeong,Jang Yu-Sin 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.S
Escherichia coli has been used as a host to construct the cell factory for biobased production of chemicals from renewable feedstocks. Because galactose is found in marine biomass as a major component, the strategy for galactose utilization in E. coli has been gained more attention. Although galactose and glucose co-fermentation has been reported using the engineered E. coli strain, few reports have covered fermentation supplemented with galactose as a sole carbon source in the mutant lacking the repressor-specific carbon catabolite repression (CCR). Here, we report the effects of the deregulation of the repressor-specific CCR (galR− and galS−) in fermentation supplemented with galactose as a sole carbon source, using the engineered E. coli strains. In the fermentation using the galR− and galS− double mutant (GR2 strain), an increase of rates in sugar consumption and cell growth was observed compared to the parent strain. In the glucose fermentation, wild-type W3110 and its mutant GR2 and GR2PZ (galR−, galS−, pfkA−, and zwf−) consumed sugar at a higher rate than those values obtained from galactose fermentation. However, the GR2P strain (galR−, galS−, and pfkA−) showed no difference between fermentations using glucose and galactose as a sole carbon source. This study provides essential information for galactose fermentation using the CCR-deregulated E. coli strains.