Some of the important factors affecting bacterial growth are: … In 1886 Francois Marie Raoult described the behaviour of an ideal solution by an equation which has since then been known as Raoult’s law: where PA is the partial vapour pressure of A above a solution, in which XA is the mole fraction of the solvent A, and PA0 is the vapour pressure of pure liquid A at the same temperature. They lack the enzymes catalase and superoxide dismutase, which catalyse the breakdown of these species as outlined below. Temperature 3. pH 4. In fruits, however, a lower pH prevents bacterial growth and spoilage is dominated by yeasts and moulds. This group of bacteria, which includes such genera as Halo-bacterium and Halo-coccus, belong to the Archaebacteria and accumulate potassium chloride as their compatible solute. If the solvent A is water then Equations (3.18) and (3.19) can be combined to give: Thus for an aqueous solution the water activity is approximately given by the ratio of the number of moles of water to the total number of moles (i.e. In fact the ability of lactic acid bacteria to acquire resistance to hop resins means that the brewery environment probably acts as a very efficient natural enrichment culture for humulone-tolerant bacteria, thus negating any beneficial effects. Obligate or strict aerobes are those organisms that are respiratory, generating most of their energy from oxidative phosphorylation using oxygen as the terminal electron acceptor in the process. If the balance of the various redox couples present favours the oxidized state then there will be a tendency to accept electrons from the electrode creating a positive potential which signifies an oxidizing environment. Welcome to BiologyDiscussion! When that same side cools down again the relative humidity increases and, although water molecules migrate back again, the temporary increase in relative humidity may be sufficient to cause local condensation onto the grain with a localized increase in aw sufficient to allow germination of fungal spores and subsequent spoilage of the grain. Microbial growth •The microbial growth is the increase in number of cells rather than in size of individual cells. Probably the supreme example of this is the white or albumen of the hen’s egg which possesses a whole battery of inhibitory components. In living cells an ordered sequence of both electron and hydrogen transfer reactions is an essential feature of the electron transport chain and energy generation by oxidative phosphorylation. The factors are: 1. Many essential cell functions such as ATP synthesis in bacteria, active transport of nutrients and cytoplasmic regulation occur at the cell membrane and are dependent on potential energy stored in the membrane in the form of a proton motive force. Carbon dioxide is not uniform in its effect on micro-organisms. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. The decrease in Eh as a result of microbial activity is the basis of some long- established rapid tests applied to foods, particularly dairy products. The same water content seems to be associated with a higher aw, in the former case than in the latter. 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