共查询到20条相似文献,搜索用时 46 毫秒
1.
Improved ethanol tolerance of Saccharomyces cerevisiae strains by increases in fatty acid unsaturation via metabolic engineering 总被引:2,自引:0,他引:2
Susumu Kajiwara Keiko Suga Hidetaka Sone Katsumi Nakamura 《Biotechnology letters》2000,22(23):1839-1843
To enhance the ethanol tolerance of Saccharomyces cerevisiae, the Arabidopsis thaliana FAD2 gene and/or the S. cerevisiae OLE1 gene were over-expressed in this yeast. The transformant over-expressing both these genes could not only synthesize dienoic fatty acids but also increased the unsaturated fatty acid content of membrane lipid and then showed the highest viability in the presence of 15% (v/v) ethanol. 相似文献
2.
Xylulose fermentation by mutant and wild-type strains of Zygosaccharomyces and Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
Eliasson A Boles E Johansson B Osterberg M Thevelein JM Spencer-Martins I Juhnke H Hahn-Hägerdal B 《Applied microbiology and biotechnology》2000,53(4):376-382
Anaerobic xylulose fermentation was compared in strains of Zygosaccharomyces and Saccharomyces cerevisiae, mutants and wild-type strains to identify host-strain background and genetic modifications beneficial to xylose fermentation.
Overexpression of the gene (XKS1) for the pentose phosphate pathway (PPP) enzyme xylulokinase (XK) increased the ethanol yield by almost 85% and resulted
in ethanol yields [0.61 C-mmol (C-mmol consumed xylulose)−1] that were close to the theoretical yield [0.67 C-mmol (C-mmol consumed xylulose)−1]. Likewise, deletion of gluconate 6-phosphate dehydrogenase (gnd1Δ) in the PPP and deletion of trehalose 6-phosphate synthase (tps1Δ) together with trehalose 6-phosphate phosphatase (tps2Δ) increased the ethanol yield by 30% and 20%, respectively. Strains deleted in the promoter of the phosphoglucose isomerase
gene (PGI1) – resulting in reduced enzyme activities – increased the ethanol yield by 15%. Deletion of ribulose 5-phosphate (rpe1Δ) in the PPP abolished ethanol formation completely. Among non-transformed and parental strains S. cerevisiae ENY. WA-1A exhibited the highest ethanol yield, 0.47 C-mmol (C-mmol consumed xylulose)−1. Other non-transformed strains produced mainly arabinitol or xylitol from xylulose under anaerobic conditions. Contrary to
previous reports S. cerevisiae T23D and CBS 8066 were not isogenic with respect to pentose metabolism. Whereas, CBS 8066 has been reported to have a high
ethanol yield on xylulose, 0.46 C-mmol (C-mmol consumed xylulose)−1 (Yu et al. 1995), T23D only formed ethanol with a yield of 0.24 C-mmol (C-mmol consumed xylulose)−1. Strains producing arabinitol did not produce xylitol and vice versa. However, overexpression of XKS1 shifted polyol formation from xylitol to arabinitol.
Received: 2 July 1999 / Accepted in revised form: 12 October 1999 相似文献
3.
Grabek-Lejko D Kurylenko OO Sibirny VA Ubiyvovk VM Penninckx M Sibirny AA 《Journal of industrial microbiology & biotechnology》2011,38(11):1853-1859
The ability of baker’s yeast Saccharomyces cerevisiae and of the thermotolerant methylotrophic yeast Hansenula polymorpha to produce ethanol during alcoholic fermentation of glucose was compared between wild-type strains and recombinant strains
possessing an elevated level of intracellular glutathione (GSH) due to overexpression of the first gene of GSH biosynthesis,
gamma-glutamylcysteine synthetase, or of the central regulatory gene of sulfur metabolism, MET4. The analyzed strains of H. polymorpha with an elevated pool of intracellular GSH were found to accumulate almost twice as much ethanol as the wild-type strain
during glucose fermentation, in contrast to GSH1-overexpressing S. cerevisiae strains, which also possessed an elevated pool of GSH. The ethanol tolerance of the GSH-overproducing strains was also determined.
For this, the wild-type strain and transformants with an elevated GSH pool were compared for their viability upon exposure
to exogenous ethanol. Unexpectedly, both S. cerevisiae and H. polymorpha transformants with a high GSH pool proved more sensitive to exogenous ethanol than the corresponding wild-type strains. 相似文献
4.
During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance. 相似文献
5.
The fermentation characteristics of the novel, thermotolerant, isolate Kluyveromyces marxianus var marxianus were determined to evaluate its aptitude for use in an ethanol production process. Sustainable growth was not observed under
anaerobic conditions, even in the presence of unsaturated fatty acid and sterol. A maximum ethanol concentration of 40 g L−1 was produced at 45°C, with an initial specific ethanol production rate of 1.7 g g−1 h−1. This was observed at ethanol concentrations below 8 g L−1 and under oxygen-limited conditions. The low ethanol tolerance and low growth under oxygen-limited conditions required for
ethanol production implied that a simple continuous process was not feasible with this yeast strain. Improved productivity
was achieved through recycling biomass into the fermenter, indicating that utilising an effective cell retention method such
as cell recycle or immobilisation, could lead to the development of a viable industrial process using this novel yeast strain.
Received 14 February 1998/ Accepted in revised form 19 May 1998 相似文献
6.
S H de Kock J C du Preez S G Kilian 《Journal of industrial microbiology & biotechnology》2000,24(4):231-236
Aerobic glucose-limited chemostat cultivations were conducted with Saccharomyces cerevisiae strains NRRL Y132, ATCC 4126 and CBS 8066, using a complex medium. At low dilution rates all three strains utilised glucose
oxidatively with high biomass yield coefficients, no ethanol production and very low steady-state residual glucose concentrations
in the culture. Above a threshold dilution rate, respiro-fermentative (oxido-reductive) metabolism commenced, with simultaneous
respiration and fermentation occurring, which is typical of Crabtree-positive yeasts. However, at high dilution rates the
three strains responded differently. At high dilution rates S. cerevisiae CBS 8066 produced 7–8 g ethanol L−1 from 20 g glucose L−1 with concomitant low levels of residual glucose, which increased markedly only close to the wash-out dilution rate. By contrast,
in the respiro-fermentative region both S. cerevisiae ATCC 4126 and NRRL Y132 produced much lower levels of ethanol (3–4 g L−1) than S. cerevisiae CBS 8066, concomitant with very high residual sugar concentrations, which was a significant deviation from Monod kinetics
and appeared to be associated either with high growth rates or with a fermentative (or respiro-fermentative) metabolism. Supplementation
of the cultures with inorganic or organic nutrients failed to improve ethanol production or glucose assimilation. Journal of Industrial Microbiology & Biotechnology (2000) 24, 231–236.
Received 09 August 1999/ Accepted in revised form 18 December 1999 相似文献
7.
Nuno P Mira Margarida Palma Joana F Guerreiro Isabel Sá-Correia 《Microbial cell factories》2010,9(1):79
Background
Acetic acid is a byproduct of Saccharomyces cerevisiae alcoholic fermentation. Together with high concentrations of ethanol and other toxic metabolites, acetic acid may contribute to fermentation arrest and reduced ethanol productivity. This weak acid is also a present in lignocellulosic hydrolysates, a highly interesting non-feedstock substrate in industrial biotechnology. Therefore, the better understanding of the molecular mechanisms underlying S. cerevisiae tolerance to acetic acid is essential for the rational selection of optimal fermentation conditions and the engineering of more robust industrial strains to be used in processes in which yeast is explored as cell factory. 相似文献8.
Towards industrial pentose-fermenting yeast strains 总被引:15,自引:0,他引:15
Hahn-Hägerdal B Karhumaa K Fonseca C Spencer-Martins I Gorwa-Grauslund MF 《Applied microbiology and biotechnology》2007,74(5):937-953
Production of bioethanol from forest and agricultural products requires a fermenting organism that converts all types of sugars
in the raw material to ethanol in high yield and with a high rate. This review summarizes recent research aiming at developing
industrial strains of Saccharomyces cerevisiae with the ability to ferment all lignocellulose-derived sugars. The properties required from the industrial yeast strains
are discussed in relation to four benchmarks: (1) process water economy, (2) inhibitor tolerance, (3) ethanol yield, and (4)
specific ethanol productivity. Of particular importance is the tolerance of the fermenting organism to fermentation inhibitors
formed during fractionation/pretreatment and hydrolysis of the raw material, which necessitates the use of robust industrial
strain background. While numerous metabolic engineering strategies have been developed in laboratory yeast strains, only a
few approaches have been realized in industrial strains. The fermentation performance of the existing industrial pentose-fermenting
S. cerevisiae strains in lignocellulose hydrolysate is reviewed. Ethanol yields of more than 0.4 g ethanol/g sugar have been achieved with
several xylose-fermenting industrial strains such as TMB 3400, TMB 3006, and 424A(LNF-ST), carrying the heterologous xylose
utilization pathway consisting of xylose reductase and xylitol dehydrogenase, which demonstrates the potential of pentose
fermentation in improving lignocellulosic ethanol production. 相似文献
9.
B. Szajáni Z. Buzás K. Dallmann I. Gimesi J. Krisch M. Tóth 《Applied microbiology and biotechnology》1996,46(2):122-125
Saccharomyces cerevisiae cells were immobilized on preformed cellulose beads by adsorption. The fermentation capacity of the immobilized yeast cells
was found to be practically independent of the hydrogen ion concentration between pH 3.1 and 6.25. The fermentation capacity
was maximal at 30 °C. The immobilized yeast cells were used for continuous production of ethanol in a fluidized-bead reactor.
The average values characteristic for the process were an ethanol concentration of 41.9±0.1 g l-1, a fermentation efficiency of 82.9±2.1% and a volumetric productivity of 3.94±0.52 g l-1 h-1.
Received: 9 October 1995/Accepted: 22 April 1996 相似文献
10.
P. J. Verbelen S. M. G. Saerens S. E. Van Mulders F. Delvaux F. R. Delvaux 《Applied microbiology and biotechnology》2009,82(6):1143-1156
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher
inoculum size). However, the decreased yeast net growth observed in these high cell density fermentations can have a negative
impact on the physiological stability throughout subsequent yeast generations. The use of different oxygen conditions (wort
aeration, wort oxygenation, yeast preoxygenation) was investigated to improve the growth yield during high cell density fermentations
and yeast metabolic and physiological parameters were assessed systematically. Together with a higher extent of growth (dependent
on the applied oxygen conditions), the fermentation power and the formation of unsaturated fatty acids were also affected.
Wort oxygenation had a significant decreasing effect on the formation of esters, which was caused by a decreased expression
of the alcohol acetyl transferase gene ATF1, compared with the other conditions. Lower glycogen and trehalose levels at the end of fermentation were observed in case
of the high cell density fermentations with oxygenated wort and the reference fermentation. The expression levels of BAP2 (encoding the branched chain amino acid permease), ERG1 (encoding squalene epoxidase), and the stress responsive gene HSP12 were predominantly influenced by the high cell concentrations, while OLE1 (encoding the fatty acid desaturase) and the oxidative stress responsive genes SOD1 and CTT1 were mainly affected by the oxygen availability per cell. These results demonstrate that optimisation of high cell density
fermentations could be achieved by improving the oxygen conditions, without drastically affecting the physiological condition
of the yeast and beer quality. 相似文献
11.
Batch and continuous cultivation of Anaerobiospirillum succiniciproducens for the production of succinic acid from whey 总被引:3,自引:0,他引:3
Batch and continuous cultivation of Anaerobiospirillum succiniciproducens were systematically studied for the production of succinic acid from whey. Addition of 2.5 g l−1 yeast extract and 2.5 g l−1 polypeptone per 10 g l−1 whey was most effective for succinic acid production from both treated and nontreated whey. When 20 g l−1 nontreated whey and 7 g l−1 glucose were used as cosubstrates, the yield and productivity of succinic acid reached at the end of fermentation were 95%
and 0.46 g (l h)−1, respectively. These values were higher than those obtained using nontreated whey alone [93% and 0.24 g (l h)−1 for 20 g l−1 whey]. Continuous fermentation of A. succiniciproducens at an optimal dilution rate resulted in the production of succinic acid with high productivity [1.35 g (l h)−1], high conversion yield (93%), and higher ratio of succinic acid to acetic acid (5.1:1) from nontreated whey.
Received: 23 July 1999 / Received revision: 17 November 1999 / Accepted: 24 December 1999 相似文献
12.
《Enzyme and microbial technology》2003,32(3-4):386-395
Low-molecular weight aliphatic acids, furaldehydes and a broad range of different aromatic compounds are known to inhibit the fermentation of lignocellulose hydrolysates by yeasts. In this work, a cocktail of different lignocellulose-derived inhibitors was used to compare the inhibitor resistance of eleven different industrial and laboratory Saccharomyces cerevisiae strains and two Zygosaccharomyces strains. The inhibitor cocktail was composed of two aliphatic acids, formic and acetic acid, two furaldehydes, furfural and 5-hydroxymethylfurfural (HMF), and two aromatic compounds, cinnamic acid and coniferyl aldehyde. Fermentations were performed under oxygen-limited conditions and with different levels (100, 75, 50, 25 and 0%) of the inhibitor cocktail present. The ethanol yield on initial glucose, the volumetric and specific ethanol productivity, the biomass yield and the glucose consumption rates were used as criteria for the performance of the strains. The results revealed major differences in inhibitor resistance between yeast strains within the same species. The ethanol yield of the S. cerevisiae strain that was least affected decreased only with 10% at an inhibitor cocktail concentration of 100%, while the decrease in ethanol yield for the most sensitive S. cerevisiae strain was more than 50% already at an inhibitor cocktail concentration of 25%. Ethanol formation was generally less affected than growth and ethanol yield less than ethanol productivity. The two most resistant strains were an S. cerevisiae strain isolated from a spent sulphite liquor plant and one of the laboratory S. cerevisiae strains. Additional fermentations with either HMF or coniferyl aldehyde revealed that the degree of resistance of different yeast strains was highly dependent on the inhibitor used. A mutant strain of S. cerevisiae displaying enhanced resistance against coniferyl aldehyde compared with the parental strains was identified. 相似文献
13.
Saccharomyces cerevisiae grows very poorly in dilute acid lignocellulosic hydrolyzate during the anaerobic fermentation for fuel ethanol production.
However, yeast cells grown aerobically on the hydrolyzate have increased tolerance for the hydrolyzate. Cultivation of yeast
on part of the hydrolyzate has therefore the potential of enabling increased ethanol productivity in the fermentation of the
hydrolyzate. To evaluate the ability of the yeast to grow in the hydrolyzate, fed-batch cultivations were run using the ethanol
concentration as input variable to control the feed-rate. The yeast then grew in an undetoxified hydrolyzate with a specific
growth rate of 0.19 h−1 by controlling the ethanol concentration at a low level during the cultivation. However, the biomass yield was lower for
the cultivation on hydrolyzate compared to synthetic media: with an ethanol set-point of 0.25 g/l the yield was 0.46 g/g on
the hydrolyzate, compared to 0.52 g/g for synthetic media. The main reason for the difference was not the ethanol production per se, but a significant production of glycerol at a high specific growth rate. The glycerol production may be attributed to an
insufficient respiratory capacity. 相似文献
14.
A Demirci A L Pometto III K-L G Ho 《Journal of industrial microbiology & biotechnology》1997,19(4):299-304
Biofilms are natural forms of cell immobilization in which microorganisms attach to solid supports. At ISU, we have developed
plastic composite-supports (PCS) (agricultural material (soybean hulls or oat hulls), complex nutrients, and polypropylene)
which stimulate biofilm formation and which supply nutrients to the attached microorganisms. Various PCS blends were initially
evaluated in repeated-batch culture-tube fermentation with Saccharomyces cerevisiae (ATCC 24859) in low organic nitrogen medium. The selected PCS (40% soybean hull, 5% soybean flour, 5% yeast extract-salt
and 50% polypropylene) was then used in continuous and repeated-batch fermentation in various media containing lowered nitrogen
content with selected PCS. During continuous fermentation, S. cerevisiae demonstrated two to 10 times higher ethanol production in PCS bioreactors than polypropylene-alone support (PPS) control.
S. cerevisiae produced 30 g L−1 ethanol on PCS with ammonium sulfate medium in repeated batch fermentation, whereas PPS-control produced 5 g L−1 ethanol. Overall, increased productivity in low cost medium can be achieved beyond conventional fermentations using this
novel bioreactor design.
Received 20 May 1997/ Accepted in revised form 29 August 1997 相似文献
15.
Eicosapentaenoic and docosahexaenoic acids production by and okara-utilizing potential of thraustochytrids 总被引:3,自引:0,他引:3
K W Fan F Chen E BG Jones L LP Vrijmoed 《Journal of industrial microbiology & biotechnology》2001,27(4):199-202
Nine thraustochytrid strains isolated from subtropical mangroves were screened for their eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA) production potential in a glucose yeast extract medium. Their ability to utilize okara (soymilk residue) for growth
and EPA and DHA production was also evaluated. EPA yield was low in most strains, while DHA level was high on glucose yeast
extract medium, producing 28.1–41.1% of total fatty acids, for all strains, with the exception of Ulkenia sp. KF13. The DHA yield of Schizochytrium mangrovei strains ranged from 747.7 to 2778.9 mg/l after 52 h of fermentation at 25°C. All strains utilized okara as a substrate for
growth, but DHA yield was lower when compared with fermentation in a glucose yeast extract medium. Journal of Industrial Microbiology & Biotechnology (2001) 27, 199–202.
Received 11 December 2000/ Accepted in revised form 29 June 2001 相似文献
16.
Carol Líliam Coelho Silva Carlos Augusto Rosa Evelyn Souza Oliveira 《World journal of microbiology & biotechnology》2006,22(8):857-863
Summary The growing demand for high quality products and the immense export potential that cacha?a represents, demonstrated especially during the past few years, have clearly indicated the necessity of establishing well-defined standards of quality, as well as effective means of controlling the process of production of this beverage. The objective of this study was the selection of S. cerevisiae yeast strains and the investigation of their influence on the kinetic parameters of fermentation. Ninety strains of S. cerevisiae isolated from distilleries of the state of Minas Gerais were evaluated with respect to the following parameters: flocculation capacity, production of H2S and kinetic parameters of fermentation. The UFMGA 905 strain was used as a reference because it presented desirable characteristics for the production of cacha?a. Five strains presented high specific sedimentation velocities (SSV), indicating a high flocculation capacity, and two did not produce H2S. The strains presented significant statistical differences for fermentation parameters: yield of ethanol; efficiency of substrate conversion to ethanol; ratio of substrate conversion to ethanol (Y
p/s), to cells (Y
x/s), to organic acids (Y
ac/s), and to glycerol (Y
g/s); and productivity. In general, the strains presented a good fermentative potential, with ethanol yields varying from 74.7 to 82.1% and an efficiency of 76.1–84.4%. All strains presented high productivities (4.6–6.6 g l−1 h−1), indicating that this parameter can be used in the selection of strains for the production of cacha?a. 相似文献
17.
Nobuo Fukuda Shinya Honda Maki Fujiwara Yuko Yoshimura Tsutomu Nakamura 《Microbial biotechnology》2021,14(3):979-992
The yeast Saccharomyces cerevisiae, widely used for ethanol production, is one of the best-understood biological systems. Diploid strains of S. cerevisiae are preferred for industrial use due to the better fermentation efficiency, in terms of vitality and endurance as compared to those of haploid strains. Whole-genome duplications is known to promote adaptive mutations in microorganisms, and allelic variations considerably contribute to the product composition in ethanol fermentation. Although fermentation can be regulated using various strains of yeast, it is quite difficult to make fine adjustment of each component in final products. In this study, we demonstrate the use of polyploids with varying gene dosage (the number of copies of a particular gene present in a genome) in the regulation of ethanol fermentation. Ethyl caproate is one of the major flavouring agents in a Japanese alcoholic beverage called sake. A point mutation in FAS2 encoding the α subunit of fatty acid synthetase induces an increase in the amount of caproic acid, a precursor of ethyl caproate. Using the FAS2 as a model, we generated and evaluated yeast strains with varying mutant gene dosage. We demonstrated the possibility to increase mutant gene dosage via loss of heterozygosity in diploid and tetraploid strains. Productivity of ethyl caproate gradually increased with mutant gene dosage among tetraploid strains. This approach can potentially be applied to a variety of yeast strain development via growth-based screening. 相似文献
18.
Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status 总被引:1,自引:0,他引:1
van Maris AJ Abbott DA Bellissimi E van den Brink J Kuyper M Luttik MA Wisselink HW Scheffers WA van Dijken JP Pronk JT 《Antonie van Leeuwenhoek》2006,90(4):391-418
Fuel ethanol production from plant biomass hydrolysates by Saccharomyces cerevisiae is of great economic and environmental significance. This paper reviews the current status with respect to alcoholic fermentation of the main plant biomass-derived monosaccharides by this yeast. Wild-type S. cerevisiae strains readily ferment glucose, mannose and fructose via the Embden–Meyerhof pathway of glycolysis, while galactose is fermented via the Leloir pathway. Construction of yeast strains that efficiently convert other potentially fermentable substrates in plant biomass hydrolysates into ethanol is a major challenge in metabolic engineering. The most abundant of these compounds is xylose. Recent metabolic and evolutionary engineering studies on S. cerevisiae strains that express a fungal xylose isomerase have enabled the rapid and efficient␣anaerobic fermentation of this pentose. l-Arabinose fermentation, based on the expression of a prokaryotic pathway in S. cerevisiae, has also been established, but needs further optimization before it can be considered for industrial implementation. In addition to these already investigated strategies, possible approaches for metabolic engineering of galacturonic acid and rhamnose fermentation by S. cerevisiae are discussed. An emerging and major challenge is to achieve the rapid transition from proof-of-principle experiments under ‘academic’ conditions (synthetic media, single substrates or simple substrate mixtures, absence of toxic inhibitors) towards efficient conversion of complex industrial substrate mixtures that contain synergistically acting inhibitors. 相似文献
19.
Instead of the conventional carbon sources used for propionic acid biosynthesis, the utilization of glycerol is considered
here, since the metabolic pathway involved in the conversion of glycerol to propionic acid is redox-neutral and energetic.
Three strains, Propionibacterium acidipropionici, Propionibacterium acnes and Clostridium propionicum were tested for their ability to convert glycerol to propionic acid during batch fermentation with initially 20 g/l glycerol.
P. acidipropionici showed higher efficiency in terms of fermentation time and conversion yield than did the other strains. The fermentation
profile of this bacterium consisted in propionic acid as the major product (0.844 mol/mol), and in minimal by-products: succinic
(0.055 mol/mol), acetic (0.023 mol/mol) and formic (0.020 mol/mol) acids and n-propanol (0.036 mol/mol). The overall propionic acid productivity was 0.18 g l−1h−1. A comparative study with glucose and lactic acid as carbon sources showed both less diversity in end-product composition
and a 17% and 13% lower propionic acid conversion yield respectively than with glycerol. Increasing the initial glycerol concentration
resulted in an enhanced productivity up to 0.36 g l−1h−1 and in a maximal propionic acid concentration of 42 g/l, while a slight decrease of the conversion yield was noticed. Such
a propionic acid production rate was similar or higher than the values obtained with lactic acid (0.35 g l−1h−1) or glucose (0.28 g l−1h−1). These results demonstrated that glycerol is a carbon source of interest for propionic acid production.
Received: 15 July 1996 / Received revision: 11 November 1996 / Accepted: 11 November 1996 相似文献
20.
The ethanol productivity of superoxide dismutase (SOD)-deficient mutants ofSaccharomyces cerevisiae was examined under the oxidative stress by Paraquat. It was observed that MnSOD-deficient mutant ofS. cerevisiae had higher ethanol productivity than wild type or CuZnSOD-deficient yeast both in aerobic and in anaerobic culture condition.
Pyruvate dehydrogenase activity decreased by 35% and alcohol dehydrogenase activity increased by 32% were observed in MnSOD-deficient
yeast grown aerobically. When generating oxygen radicals by Paraquat, the ethanol productivity was increased by 40% in CuZnSOD-deficient
or wild strain, resulting from increased activity of alcohol dehydrogenase and decreased activity of pyruvate dehydrogenase.
However, the addition of ascorbic acid with Paraquat returned the enzyme activities at the level of control. These results
imply that SOD-deficiency in yeast strains may cause the metabolic flux to shift into anaerobic ethanol fermentation in order
to avoid their oxidative damages by Paraquat. 相似文献