Fermentation microbial kinetics

The denominator in equation 5.157 is clearly less than unity, provided the separator has any concentrating ability (i.e. works at all). As in the case for the expression linking D and n (equation 5.131) for a simple CSTF, it is independent of the microbial kinetics. If R - 0 or 4= 1 then equation 5.157 reduces to equation 5.131, corresponding to a CSTF at steady-state with no recycle. The effect of the recycle is to allow the fermenter to be operated at higher dilution rates than would otherwise be possible. 

The differential equations shown in the Microbial Kinetics section are used to describe the batch fermentation mode. These... 

Mitchell DA, Stuart DM, Tanner RD (1999) Solid-state fermentation - microbial growth kinetics. In Flickinger MC, Drew SW (eds) The encyclopedia of bioprocess technology fermentation, biocatalysis and bioseparation, vol 5. WUey, New York, p 2407 Saucedo-Casteneda G, Gutierrez-Rojas M, Bacquet G, Raimbault M, Viniegra-Gonzalez G (1990) Biotechnol Bioeng 35 802... 

B., and Enfors, S.O. (2001) CMA integration of fluid dynamics and microbial kinetics in modelling of large-scale fermentations. Chem. Eng. Sci., 84,... 

Jin, Q., 2007, Control of hydrogen partial pressures on the rates of syntrophic microbial metabolisms a kinetic model for butyrate fermentation. Geobiology 5, 35-48. 

When a pilot-scale fermenter is run in continuous mode with a fresh feed flowrate of 65 1/h, the effluent from the fermenter contains 12 mg/1 of the original substrate. The same fermenter is then connected to a settler-thickener which has the ability to concentrate the biomass in the effluent from the tank by a factor of 3.2, and from this a recycle stream of concentrated biomass is set up. The flowrate of this stream is 40 1/h and the fresh feed flowrate is at the same time increased to 100 1/h. Assuming that the microbial system follows Monod kinetics, calculate the concentration of the final clarified liquid effluent from the system. /x, = 0.15 h-1 and Ks = 95 mg/1. 

Two continuous stirred-tank fermenters are arranged in series such that the effluent of one forms the feed stream of the other. The first fermenter has a working volume of 100 1 and the other has a working volume of 50 1. The volumetric flowrate through the fermenters is 18 h-1 and the substrate concentration in the fresh feed is 5 g/1. If the microbial growth follows Monod kinetics with //, = 0.25 h-1, Ks = 0.12 g/1, and the yield coefficient is 0.42, calculate the substrate and biomass concentrations in the effluent from the second vessel. What would happen if the flow were from the 50 1 fermenter to the 100 1 fermenter ... 

During microbial action, kinetic isotope fractionations on the organic material by methanogenic bacteria result in methane that is highly depleted in typically with 5 C-values between -110 and -50%c (Schoell 1984, 1988 Rice and Claypool 1981 Whiticar et al. 1986). In marine sediments, methane formed by CO2 reduction is often more depleted in than methane formed by acetate fermentation in freshwater sediments. Thus, typical ranges for marine sediments are between -110 and -60%c, while those for methane from freshwater sediments are from -65 to -50%c (Whiticar et al. 1986 Whiticar 1999). 

General Kinetic Expression. The simplest expression of the Monod type which can account for both factors in microbial fermentation is... 

In contrast to the batch fermentation based methods of determining kinetic constants, the use of a continuous fermenter (Fig. 3.71) requires more experiments to be performed, but the analysis tends to be more straightforward. In essence, the experimental method involves setting up a continuous stirred-tank fermenter to grow the micro-organisms on a sterile feed of the required substrate. The feed flowrate is adjusted to the desired value which, of course, must produce a dilution rate below the critical value for washout, and the system is allowed to reach steady state. Careful measurements of the microbial density X, the substrate concentration S, and the flowrate F are made when a steady state has been achieved, and the operation is then repeated at a series of suitable dilution rates. 

Understanding the growth kinetics of microbial, animal, or plant cells is important for the design and operation of fermentation systems employing them. Cell kinetics deals with the rate of cell growth and how it is affected by various chemical and physical conditions. 

You need to cultivate hypothetical microbial cells with the Monod kinetic parameter values of ymax = 5.0 hr-1 and Ks = 20 g/L. The cell yield (Yx/S) is 0.4 and the substrate concentration is 30 g/L. The required substrate conversion is 97%. Estimate the residence time required for the following fermenter configurations... 

Ethanol is consumed widely. Microbial fermentation in the large intestine of humans can produce about 3 g of ethanol per day. Ethanol is rapidly absorbed throughout the gastrointestinal tract or, when inhaled, through the lungs. It is metabolized in the liver by a process having zero-order kinetics i.e., the rate of oxidation is constant with time. The amount metabolized per unit time depends on... 

Lan, Y. B.A. Williams S. Tamminga H. Boer A. Akkermans G. Erdi M.W.A. Verstegen. In vitro fermentation kinetics of some non-digestible carbohydrates by the caecal microbial community of broilers. Anim. Feed Sci. Technol. 2005, 123-124, 687-702. 

Degeest, B., Vaningelgem, R, De Vuyst, L. (2001). Microbial physiology, fermentation kinetics, and process engineering of heteropolysaccharide production by lactic acid bacteria. International Dairy Journal, 11(9), 747-757. 

Data about the physical characteristics of a bioreactor can provide only limited information. The complete characterization of a bioreactor requires additional studies involving biological test systems ( reference fermentations ). The fluid dynamics and rheological behavior of media are both directly and indirectly influenced by the presence of biological cells (Fiechter, 1978). Microbial processes whose growth or production kinetics are specifically dependent on changes in their medium or the reactor come into consideration as biological test systems (Karrer, 1978). Because of the central role of mass... 

This picture can be used to demonstrate that enzymatic reactions are the center of kinetic considerations for microbial systems, even if it is hard to verify directly such a mechanistic approach in real fermentations. 

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