Fermentations temperature effects

The pH is adjusted to 6.9 to 7.0 before sterilization and aerobic fermentation is effected for 24 hours (until the packed cell volume is about 10 to 15%) under the following conditions temperature, 37°C sterile air input, 54 ftVmin pressure, 7 psi and agitation,... 

Cloughley, J. B., The effect of fermentation temperature on the quality parameters and price evaluation of Central African black teas. J. Sci. Food Agri., 31 911, 1980. 

Suppose we are interested in investigating the effect of fermentation temperature on the percent alcohol response of the wine-making system shown in Figure 1.6. We will assume that ambient pressure has very little effect on the system and that the small variations in response caused by this uncontrolled factor can be included in the residuals. Further, we can use the same type and quantity of yeast in all of our experiments so there will be no (or very little) variation in our results caused by the factor yeast . 

A summary of the factors which are known to influence ethanol production from glucose in a gas-solid fluidized bed fermenter, or which may have an influence based on observations with submerged fermentations, is shown in Figure 6.1. In anaerobic beds, the key factors are the fermentation temperature and ethanol inhibition, both of which have a dramatic effect on the specific rafe of ethanol production. Bed dehydration and its influence on yeast pellet moisture content is also important, since a failure of fermentation may occur if the pellets become too dry (Bauer, 1986). 

To show correlation between occurrence of malo-lactic fermentation and bacterial inoculation, and to show consistency of results among the control lots and inoculated lots, it is imperative that the division of lots be made before alcoholic fermentation. For red wines, great care must be taken to obtain equitable distribution of the crushed grapes in each of the lots. The inconsistency in the results mentioned above may have been caused by variation in amounts of grape skins during the alcoholic fermentation with the accompanying effect on fermentation temperature, sulfur dioxide concentration,. pH after pressing, and concentration of nutrients (55, 56). 

Let us carry out a so-called screening experiment in which we attempt to discover if the fermentation temperature (factor x ) has a significant effect on the response (% alcohol content). We will choose two levels of temperature, 23°C and 27°C. This is the minimal number of factor levels required to fit the two-parameter model... 

Yokoyama, H., Waki, M., Moriya, N., Yasuda, T., Tanaka, Y., and Haga, K. 2007. Effect of fermentation temperature on hydrogen production from cow waste slurry by using anaerobic microflora within the slurry. Appl. Microbiol. Biotechnol., 74, 474 183. 

In this study, ethanol extraction using SC CO2 was achieved from 15 to 75 %(v/v) synthetic ethanol solutions and also from fermentation broth. Effects of temperature, pressure, extraction time and initial ethanol concentration on extraction yield were investigated in the ranges of 313 to 333 K and 80 to 160 atmospheres. Optimum conditions for the batch extraction of 15%(v/v) ethanol solution were found using the Box-Wilson optimization method in a linear form. In addition, the effect of consecutive solvent feeding on extraction yield were investigated both with 15 %(v/v) ethanol solution and with fermentation broth. 

Torrija, M.J., Beltran, G., Novo, M.T., Poblet, M., Guillamon, J.M., Mas, A., Rozes, N. (2003) Effect of fermentation temperature and Saccharomyces species on the cell fatty acid composition and presence of volatile compounds in wine. Int. J. Food Microbiol., 85, 127-136. 

Delaquis, R, Cliff, M., King, M., Girare, B., Hall, J., Reynolds, A. (2000). Effect of two commercial malolactic cultures on the chemical and sensory properties of Chancellor wines vinified with different yeasts and fermentation temperatures. Am. J. EnoL Vitic., 51, 42 8. 

Yeast strain, and nutrient status of the must and fermentation conditions, many of which affect growth or induce physiological stress, modulate the accumulation of acetic and other fatty acids in wine. Reported factors include must sugar concentration, nutrient balance, inoculum level, fermentation temperature, pH and aeration (Delfini and Costa 1993 Henschke and Jiranek 1993 Shimazu and Watanabe 1981). The effects of osmotic stress, as induced by sugar concentration, on acetic acid production are discussed in Sect. 8D.3.2. 

Figure 4 shows the effect of fermentation temperature on K, for acetic acid. The resulting equation, of the form of the Arrhenius equation, which describes this relationship is ... 

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 ... 

Figure 7. Predicted effect of fermentation temperature on effluent biodegradable COD concentration and treatment efficiency for a complex waste...

Ough, C.S. 1966. Fermentation rates of grape juice. II. Effect of initial Brix, pH, and fermentation temperature. Am. J. Enol. Vitic. 17, 20-26. 

Hsin-Yu, C. and Chou, C.-C. 2001. Acid adaptation and temperature effect on the survival of E. coli 0157 H7 in acidic fruit juice and lactic fermented milk product. International Journal of Food Microbiology 70 189-195. 

The operating conditions are very important for efficient cellulase production via solid-state fermentation. The effects of operating conditions, such as temperature, water content and water activity, pH, aeration and substrate composition, on the cellulase production by solid-state fermentation will be discussed in this section. 

The theoretical agitation effect of aeration alone can be easily calculated. There are two separate forces, the first caused by the free rise of bubbles. The bubbles rise from the sparger at a pressure equal to the hydrostatic pressure of the liquid and as they rise to the surface, the gas bubble pressure remains in constant equilibrium with the hydrostatic pressure above it until it escapes fi om the liquid surface. The temperature of the air in the bubble is equal to the fermentation temperature and remains constant due to heat transfer from the fermentation broth. These conditions describe an isothermal expansion of gas gas pressure and gas volume change at constant temperature. Using the formula from Perry and Chilton,the theoretical horsepower for the isothermal expansion of air can be calculated. 

Salovaara, H. and Valjakka, T. 1987. The effect of fermentation temperature, flour type, and starter on the properties of sour wheat bread. Int. J. Food Sci. Technol. 22, 591-597. 

The effect of lowering the temperature is typically attributed to decreased proteolysis and unfolding of the protein. The lack of a clear increase in the rMnP yield by P. pastoris oMnPl-1 upon lowering the fermentation temperature suggests that, at pH 6, spontaneous denaturation and protease activity do not limit the final active rMnP enzyme yield. 

Refrigerating the environment is another way of utilizing cold to stabilize wine. Winter cold may be used for this purpose, as well as specialized vat room installations where a chilled atmosphere makes it possible to keep wine at a temperature in the vicinity of 0°C for one or two months. The wine must previously have been filtered. Vats may be equipped with individual exchangers to accelerate cooling. This type of installation is highly effective. Furthermore, it minimizes the risk of oxidation, as the wine does not need to be handled. This system may also be used for fermenting white wines, maintaining a fermentation temperature of around 18-20°C, or even lower. 

---