Ethanol, fermentation Zymomonas mobilis

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... 

McMillan, J., M. Newman, D. Templeton and A. Mohagheghi (1999). Simultaneous saccharification and cofermentation of dilute-acid pretreated yellow poplar hardwood to ethanol using xylose-fermenting Zymomonas mobilis Applied Biochemistry and Biotechnology 79(1) 649-665. 

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

Weuster-Botz, D., Aivasidis, A., and Wandrey, C., Continuous Ethanol Production by Zymomonas mobilis in a Fluidized Bed Reactor. Part II. Process Development for the Fermentation of Hydrolysed B-Starch without Sterilization, Appl. Microbiol. Biotechnol., 39 685 (1993)... 

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. 

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. 

The parameters of this model offer a physiologically adequate description of the growth and fermentation of Zymomonas mobilis. Furthermore, this model is highly consistent with experimental fermentor data. Specifically, it predicts the response of the steady state RNA content of the biomass to elevated ethanol concentrations qualitatively. The effect of an elevated ethanol concentration on the fermentation kinetics resembles the effect of elevating the temperature of the fermentation broth. 

Favela-Torres, E., Allais, J.-J., and Baratti, J., Kinetics of batch fermentation for ethanol production with Zymomonas mobilis growing on Jerusalem artichoke juice, Biotechnol. Bioeng., 28, 850-856, 1986. 

Alcoholic fermentation is the anaerobic transformation of sugars, mainly glucose and fructose, into ethanol and carbon dioxide. This process, which is carried out by yeast and also by some bacteria such as Zymomonas mobilis, can be summarised by this overall reaction. 

Metabolic engineering [39, 40] has been used to impart the capacity for ethanol production and xylose fermentation in E. coli [41-45], Klebsiella oxytoca [A6,A7],Zymomonas mobilis [48,49] andS. cerevisiae [50-53]. In general, attempts at metabolic engineering have been more successful in bacteria than in yeasts. Although the reasons are not entirely clear, the smaller genomes and fewer feedback regulatory factors found in bacteria make these organisms much easier to work with. 

Behera S., Mohanty R.C. and Ray R.C. Ethanol fermentation of sugarcane molasses by Zymomonas mobilis MTCC 92 immobilized in Luffa cylindrica L. sponge discs and Ca-alginate matrices. Brazilian Journal of Microbiology 43 (4) (2012) 1499-1507. 

Doran, J.B. and Ingram, L.O. (1993) Fermentation of crystalline cellulose to ethanol by Klebsiella oxytoca containing chromosomally integrated Zymomonas mobilis genes. BiotechnoL Progr., 9, 533-538. 

Golias H, Dumsday GJ, Stanley GA, Pamment NB. (2002). Evaluation of a recombinant Kfeb-siella oxytoca strain for ethanol production from cellulose by simultaneous saccharification and fermentation comparison with native cellobiose utilizing yeast strains and performance in co-culture with thermotolerant yeast and Zymomonas mobilis. J Biotechnol, 96,155-168. 

Lee KJ, Lefebvre M, Tribe DE, Rogers PL. (1980). High productivity ethanol fermentations with Zymomonas mobilis using continuous cell recycle. Biotechnol Lett, 2, 487-492. 

Enzymes can convert lignocellulosic biomass into a suitable fermentation feed-stock for biofuel production. Different yeast strains are used for ethanol production, such as S. diastaticus, Candida sp., S. cerevisiae and K. marxianus, as well as different bacteria such as Zymomonas mobilis. The employment of distillation is desirable for food grade purity of applications other than that of biofuel. In fact, batch fermentation was coupled with a membrane distillation process developed with the application of a membrane distillation bioreactor for ethanol production. Meanwhile,... 

In vivo, pyruvate decarboxylase [EC 4.1.1.1] catalyzes the nonoxidative decarboxylation of pyruvate to acetaldehyde and is thus a key enzyme in the fermentative production of ethanol. The most well-studied PE)Cs are obtained from baker s yeast [1477, 1482, 1483] and from Zymomonas mobilis [1484]. 

Jobses, I. M. L and Roels, J. A. The inhibition of the maximum specific growth and fermentation rate of Zymomonas mobilis by ethanol. Biotechnol. Bioeng. 28(4), 554-563, 1986. 

Jobses and Roels (3) proposed a four-dimensional model to simulate the oscillatory behavior of ethanol fermentation using Zymomonas mobilis. Four state variables in the model are X (micro-organisms), e (an internal key component related to the rate of growth of micro-organism), S (substrate i.e., sugar), and P (product i.e., ethanol). The rates of formation of these variables obtained in batch experiments are... 

Jobses, I. M. L., Egberts, G. T. C., Luyben, K. C. A. M., and Roels, J. A. Fermentation kinetics of Zymomonas mobilis at high ethanol concentrations oscillations in continuous cultures. Biotechnol. Bioeng. 28, 868-877, 1986. Daugulis, A. J., McLellan, P. J., and Li, J. Experimental investigation and modeling of oscillatory behavior in the continuous culture of Zymomonas mobilis. Biotechnol. Bioeng. 56, 99-105, 1997. 

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