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Isolation and preliminary characterization of a Zymomonas mobilis mutant with an altered preference for xylose and glucose utilization 总被引:1,自引:0,他引:1
Shane G. Supple Eva L. Joachimsthal Noel W. Dunn Peter L. Rogers 《Biotechnology letters》2000,22(2):157-164
The narrow substrate range of Zymomonas mobilis CP4 has been extended previously to include metabolism of the pentose sugar, xylose, by Zhang et al. (Science
267: 240–243). The strain CP4(pZB5) co-ferments both glucose and xylose in mixed sugar fermentations, however glucose is utilized preferentially. The present work reports the isolation of a new mutant from CP4(pZB5) which displays an altered carbon substrate preference. The mutant, CP4(pZB5) M1-2, metabolizes xylose more rapidly than glucose in mixed glucose/xylose media. Sequence data analysis revealed mutations in both the glucose facilitator (glf) and glucokinase (glk) genes. 相似文献
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B S Dien L B Iten R J Bothast 《Journal of industrial microbiology & biotechnology》1999,22(6):575-581
Escherichia coli strain FBR3 that is an efficient biocatalyst for converting mixed sugar streams (eg, arabinose, glucose, and xylose) into
ethanol. In this report, the strain was tested for conversion of corn fiber hydrolysates into ethanol. Corn fiber hydrolysates
with total sugar concentrations of 7.5% (w/v) were prepared by reacting corn fiber with dilute sulfuric acid at 145°C. Initial
fermentations of the hydrolysate by strain FBR3 had lag times of approximately 30 h judged by ethanol production. Further
experiments indicated that the acetate present in the hydrolysate could not solely account for the long lag. The lag phase
was greatly reduced by growing the pre-seed and seed cultures on corn fiber hydrolysate. Ethanol yields for the optimized
fermentations were 90% of theoretical. Maximum ethanol concentrations were 2.80% w/v, and the fermentations were completed
in approximately 50 h. The optimal pH for the fermentation was 6.5. Below this pH, sugar consumption was incomplete and above
it, excess base addition was required throughout the fermentation. Two alternative neutralization methods (overliming and
overliming with sulfite addition) have been reported for improving the fermentability of lignocellulosic hydrolysates. These
methods further reduced the lag phase of the fermentation, albeit by a minor amount.
Received 29 September 1998/ Accepted in revised form 20 February 1999 相似文献
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Candida guilliermondii grew on the d- and l-isomers of arabinose, xylose, ribose and lyxose. Xylose reductase was extracted from xylose-grown cells and the enzyme was purified to homogeneity. The purified enzyme used NADPH as a cosubstrate, had a molecular weight of 36000 Da and pI of 4.5. It reduced the d- and l-forms of all the above pentoses. 相似文献
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A new 14-step synthesis of (+)-oxybiotin, an oxygen analogue of (+)-biotin, was achieved starting from D-xylose by use of selected 2,5-anhydro sugar derivatives as key intermediates. 相似文献
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Recombinant Escherichia coli engineered for production of L-lactic acid from hexose and pentose sugars 总被引:4,自引:0,他引:4
B S Dien N N Nichols R J Bothast 《Journal of industrial microbiology & biotechnology》2001,27(4):259-264
Recombinant Escherichia coli have been constructed for the conversion of glucose as well as pentose sugars into L-lactic acid. The strains carry the lactate dehydrogenase gene from Streptococcus bovis on a low copy number plasmid for production of L-lactate. Three E. coli strains were transformed with the plasmid for producing L-lactic acid. Strains FBR9 and FBR11 were serially transferred 10 times in anaerobic cultures in sugar-limited medium containing
glucose or xylose without selective antibiotic. An average of 96% of both FBR9 and FBR11 cells maintained pVALDH1 in anaerobic
cultures. The fermentation performances of FBR9, FBR10, and FBR11 were compared in pH-controlled batch fermentations with
medium containing 10% w/v glucose. Fermentation results were superior for FBR11, an E. coli B strain, compared to those observed for FBR9 or FBR10. FBR11 exhausted the glucose within 30 h, and the maximum lactic acid
concentration (7.32% w/v) was 93% of the theoretical maximum. The other side-products detected were cell mass and succinic
acid (0.5 g/l). Journal of Industrial Microbiology & Biotechnology (2001) 27, 259–264.
Received 05 November 2000/ Accepted in revised form 03 July 2001 相似文献
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