Fermentation kinetics temperature effects

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. 

Excessive temperatures and sugar concentrations can provoke sluggish or stuck fermentations. Nutritional deficiencies and inhibition phenomena can also be involved. All of them have either chemical or physicochemical origins. Fermentation kinetics can be ameliorated by different methods which influence these phenomena. Early action appears to increase their effectiveness yeasts in their growth phase and in a medium containing little ethanol are more receptive to external stimuli. The winemaker should anticipate fermentation difficulties the possible operations are much less effective after they occur. 

Fermentation rates have been observed to vary under apparently identical conditions (temperature, sugar content, amount of yeast inoculated, etc.). Sluggish fermentations may be completed successfully, but they are always a cause for concern. Besides specific factors in the must, one explanation is that several yeast sfiains are involved and fermentation kinetics may be affected by antagonism between them (Killer effect. Sections 1.7 and 3.8.1). 

Fermentation Temperature. The effects of fermentation temperature on performance of anaerobic biological processes have been described here as a temperature dependency of the kinetic coefficients k and Kg (Figure 4 for acetate). O Rourke (3), using the kinetic information in Table VI, developed the following equations of the form of Equation 20 to define the temperature dependency of k and K,. for a complex waste over the temperature range of 20°-35°C ... 

Watier, D., Chowdhury, L, Leguerinel, I., Homez, J. P. (1996h). Response surface models to describe the effects of temperature, pH, and ethanol concentration on growth kinetics and fermentation end products of a Pectinatus sp. Applied and Envrionmental Microbiology, 62, 1233-1237. 

Schafer et al. used several spectroscopic techniques to characterize the surface species on phosphate-modified zirconia particles. Their results show that phosphate merely adsorbs on the surface of zirconia under the mildest phosphate concentration, i.e., neutral pH, room temperature, and short contact times. However, at acidic pH and higher temperarnres, esterification of the phosphate with surface hydroxyls takes place as the kinetic barriers are overcome. The solid NMR studies clearly show the presence of covalently bound phosphate. This phosphate modification effectively blocks the sites responsible for the strong interaction of certain Lewis bases with the zirconia surface, resulting in a more biocompatible stationary phase. Unlike fluoride-modified zirconia, phosphate-modified zirconia behaves as a classic cation exchanger and not as a mixed-mode medium analogous to hydroxyapatite, despite spectroscopic evidence of zirconium phosphate formation on the surface. This limits the applicability of the supports, as most proteins and enzymes are anionic at neutral pH. Nevertheless, its ability to separate proteins with high p/ values still deserves much attention. The preparative-scale separation of murine IgGs from a fermentation broth demonstrates the utiUty of the supports for solutes that are retained. 

Alcoholic fermentation is an exothermic reaction (generating heat), and its kinetics (velocity of the reaction) depends strongly on temperature. Several factors affect the course of fermentation (e.g., pH, alcohol concentration, high salt concentration), but temperamre has the greatest effect. Several research studies have shown that the optimum temperature for S. cerevisiae in alcoholic fermentation is close to 32 °C (Costa et al. 2009). 

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