Zymomonas

The genus Zymomonas belongs to the phylum Proteobacteria, the class Alphapro-teobacteria, the order Sphingomonadales and the family Sphingomonadaceae. Zymomonas to date has only one species, cited as Z. mobilis, which was formerly known as Achromobacter anaerobium, originally isolated from beer (Shimwell, 1936). In the older literature, Zymomonas has been cited as Saccharomonas lindneri and Pseudomonas lindneri (Hornsey, 2013). 

At present, Z. mobilis has three validated subspecies, namely Z. mobilis subsp. pomaceae (Millis, 1956 De Ley Swings, 1976), Z. mobilis subsp. mobilis (Lindner, 1928 De Ley Swings, 1976) and Z. mobilis subsp. francensis (Coton, Laplace, Auffray, Coton, 2005a). All three subspecies are differentiated based on phenotypic characterisation, protein and genetic characterisation and growth at 36 °C 

The original source of contamination by Zymomonas species in the brewery and cider house is still unknown. Soil is suggested to be the possible source of contamination in beer (Ingledew, 1979 Coton Coton, 2003), as incidents of Z. mobilis contamination are linked to times of construction of new facilities and excavation in breweries (Ingledew, 1979). Z. mobilis subsp. mobilis has also been reported to prevail in public houses, well-water sources, soil from brewery environments and the bottling process (Dads Martin, 1978 Swings De Ley, 1977). 

Z mofe j/w-contaminated beer has a fruity aroma (rotten apple, due to the production of acetaldehyde), which rapidly progresses to a sulphidic and rotten-egg aroma (due to the production of hydrogen sulphide) in spoiled beer (Dads Martin, 1978). The contamination incidents due to Zymomonas are limited to ales supplemented with primed sugar and spoilage problems due to these bacteria have never been encountered in lager beers (Dads Martin, 1978 Bokulich Bamforth, 2013 Richards Corbey, 1974). 

The genes encoding two enzymes from the TCA cycle the 2-oxoglutarate dehydrogenase complex and malate dehydrogenase for the TCA cycle are reported to be 

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The formation of optically active acyloins is also catalyzed by the yeast Candida Pareri if the bacteria Zymomonas mobilis and Zymomonas carlbergensis42 and the fungus Diplodia gossypina43. The latter microorganism produces (3/ ,66 )-6-hydroxy-7-oxo-8-norcitronellene from (/ )-citronellene by a reaction sequence that converts (7d)-citronellene to (/ )-4-methyl-5-butenal followed by addition of the acetyl moiety to the / e-face of the aldehyde. 

Owing to diminishing fossil fuel reserves, alternative energy sources need to be renewable, sustainable, efficient, cost-effective, convenient and safe.1 In recent decades, microbial production of ethanol has been considered as an alternative fuel for the future because fossil fuels are depleting. Several microorganisms, including Clostridium sp. and yeast, the well-known ethanol producers Saccharomyces cerevisiae and Zymomonas mobilis, are suitable candidates to produce ethanol.2,3... 

Use of biofilm reactors for ethanol production has been investigated to improve the economics and performance of fermentation processes.8 Immobilisation of microbial cells for fermentation has been developed to eliminate inhibition caused by high concentrations of substrate and product, also to enhance productivity and yield of ethanol. Recent work on ethanol production in an immobilised cell reactor (ICR) showed that production of ethanol using Zymomonas mobilis was doubled.9 The immobilised recombinant Z. mobilis was also successfully used with high concentrations of sugar (12%-15%).10... 

Gunasekaran, P. and Raj, K.C., 2001. Ethanol fermentation technology - Zymomonas mobilis, httn //ces.iisc.ernet.in/curscinew/iulvl0/articlesl4.htm. 

There are two popular microorganisms that can produce high concentrations of alcohol. Their tolerance to high concentrations of ethanol and substrates are stated in the literature.3-5 The most common are Zymomonas mobilis and Saccharomyces cerevisiae. 

Strohhacker J, AA de Graaf, SM Schoberth, RM Wittig, H Sahm (1993) P nuclear magnetic resonance studies of ethanol inhibition in Zymomonas mobilis. Arch Microbiol 159 484 90. 

Jung, H.C., Lebeault, J.M. and Pan, J.G. (1998) Surface display of Zymomonas mobilis levansucrase by using the ice-nucleation protein of Pseudomonas syringae. Nature Biotechnology, 16, 576-580. 

Use of bioflocs rather than supported film particles will maximize the effectiveness factor for a given particle, but uneven growth of floes can cause severe stratification in the bed. If stratification can be overcome by methods such as the use of a tapered bed to control porosity the removal, breaking up, and recycle of biomass at the bottom of the bed or, ideally, the use of microbial strains or species that will stop growing at a desirable floe size, such as a Zymomonas mobilis strain that stops growing at one millimeter in diameter (Scott, 1983), the use of bioflocs rather than support particles can improve reactor productivity. 

Scott, C. D., Ethanol Production in a Fluidized-Bed Bioreactor Utilizing Flocculating Zymomonas Mobilis with Biomass Recycle, Biotechnol. Bioeng. Symp. Ser., 13 287 (1983)... 

Weuster, D., Aivasidis, A., and Wandrey, C., Ethanolfermentation of Sugar Containing Wastes with Zymomonas mobilis in a Fluidized Bed Reactor, DECHEMA Biotechnol. Con/., 3 507 (1989)... 

Weuster-Botz, D., Continuous Ethanol Production by Zymomonas mobilis in a Fluidized Bed Reactor. Part I. Kinetic Studies of Immobilization in Macroporous Glass Beads, Appl. Microbiol. Biotechnol., 39 679 (1993)... 

K. B. Song, J. W. Seo, and S. K. Rhee, Transcriptional analysis of levU operon encoding saccharolytic enzymes and two apparent genes involved in amino acid biosynthesis in Zymomonas mobilis, Gene, 232 (1999) 107-114. 

Secondary active uniport systems facilitating the permeation of a single solute, dependent on the electrochemical potentials of the solute molecules, are rare in bacteria. Only a glucose uptake system of Zymomonas mobilis has been studied in more detail [101]. 

Recently, Edye et al, (4) described a fermentation process which used a mutant strain of Zymomonas mobilis to produce high concentrations of fructose and ethanol when grown on a concentrated sucrose medium. Johns and Greenfield (5) proposed ethanolIc crystallization as a means of recovering the fructose from the broth. The kinetic behaviour of fructose crystallization from ethanolIc solution has not been previously reported, and this work Investigates these crystallization kinetics. 

Krishnan, M.S., Blanco, M., Shattuck, G.K., Nghiem, N.P and Davison, B.H., Ethanol production from glucose and xylose by immobilized Zymomonas mobtlis GP4(pZB5), Appl. Biochem. Biotech., 84 (2000) 525-542. 

Different simple correlations between biomass and fluorescence data showed that on-line estimation is possible under strictly defined culture conditions. Even a strictly finear relation between biomass and culture fluorescence was found for the growth of Zymomonas mobilis, Methylomonas mucosa, and Pseudomonas putida under non-limited conditions [47]. 

PPD from another bacterium was characterized by the Dunaway-Mariano group [26], Based on the PDC structure from Zymomonas mobilis and other ThDP enzymes [27], a hypothetical model for PPD was built. This model was then corroborated by site-directed mutagenesis of all the amino acid residues at the ThDP and phosphonopyruvate binding sites [25]. A hypothetical working model for the PPD active site is given in Fig. 2.2.2.2. 

Fig. 2.2.2.2 Postulated model of the active site of phosphonopyruvate decarboxylase. PPD from Str. viridochromogenes T0494 (based on the structure of PDC from Zymomonas mobilis [27] and data from analyis of site-directed mutants [25]). The model depicts the start of the catalytic reaction (deprotonation of the reactive C2 atom (yellow) on the thiazolium ring ofThDP...

In order to increase the understanding of ThDP-dependent enzymes, the identification of amino acid side chains important for the catalysis of the carboligase reaction in pyruvate decarboxylase from Zymomonas mohilis (E.C. 4.1.1.1) and benzoylformate decarboxylase from Pseudomonasputida (E.C. 4.1.1.7) was a major task. Using site-directed mutagenesis and directed evolution, various enzyme variants were obtained, differing in substrate specificity and enantioselectivity. 

D. Dohritzsch, S. Konig, G. Schneider, G. Lu, High resolution crystal structure of pyruvate decarboxylase from Zymomonas mohilis. Implications for substrate activation in pyruvate decarboxylases. J. Biol. Chem. 1998, 273, 20 196-20 204. 

G. Goetz, P. Iwan, B. Hauer, M. Breuer, M. Pohl, Continuous production of (R)-phenylacetylcarbinol in an enzyme-membrane reactor using a potent mutant of pyruvate decarboxylase from Zymomonas mohilis. Biotechnol. Bioeng. 2001, 74, 317-325. 

M. Pohl, Exchanging the substrate specificities of pyruvate decarboxylase from Zymomonas mohilis and benzoylformate decarboxylase from Pseudomonas putida. Protein Eng. Des. 

Pawluk, A. Scopes, R.K. Griffiths-Smith, K. Isolation and properties of the glycolytic enzymes from Zymomonas mobilis. The five enzymes from gly-ceraldehyde-3-phosphate dehydrogenase through to pyruvate kinase. Biochem. J., 238, 275-281 (1986)... 

An additional way of cleaving a six-carbon sugar chain provides the basis for the Entner-Doudoroff pathway which is used by Zymomonas lindneri and many other species of bacteria. Glucose 6-P is oxidized first to 6-phosphogluconate, which is converted by dehydration to a 2-oxo-3-deoxy derivative (Eq. 17-18,... 

Some lactic acid bacteria of the genus Lactobacillus, as well as Leuconostoc mesenteroides and Zymomonas mobilis, carry out the heterolactic fermentation (Eq. 17-33) which is based on the reactions of the pentose phosphate pathway. These organisms lack aldolase, the key enzyme necessary for cleavage of fructose 1,6-bisphosphate to the triose phosphates. Glucose is converted to ribulose 5-P using the oxidative reactions of the pentose phosphate pathway. The ribulose-phosphate is cleaved by phosphoketolase (Eq. 14-23) to acetyl-phosphate and glyceraldehyde 3-phosphate, which are converted to ethanol and lactate, respectively. The overall yield is only one ATP per glucose fermented. 

Preziosi, L, Michel, G. P. F, and Baratti, J. (1990) Characterisation of sucrose hydrolising enzymes of Zymomonas mobilis Arch Microbiol. 153, 181-186. 

Ethanol Saccharomyces cerevisiae, Zymomonas mobilis, Clostridium thermocellum and other Clostridium spp. Alcoholic beverages solvent in chemical industry fuel extender... 

Fig. 5.21. The end-products (circled) of microbial fermentations of pyruvate. Letters indicate the organisms able to perform these reactions. (/<) Lactic acid bacteria (Streptococcus, Lactobacillus) (B) Clostridium propionicum (C) Yeast, Zymomonas mobilis, Sarcina ventriculr, (D) Enterobacteriaceae (Coli-aerogenes) (E) Clostridia, ...

RA Moreau, MJ Powell, SF Osman, BD Whitaker, WF Fett, L Roth, DJ O Brien. Analysis of intact hopanoids and other lipids from the bacterium Zymomonas mobilis by high performance liquid chromatography. Anal Biochem 224 293-301, 1995. 

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