Aerobic organism growth

The bacterium Lactobacillus plantarum and its closest allies are unusual in that they are aerobic organisms but do not produce a superoxide dismutase. This bacterium instead accumulates Mn(II) to an intramolecular level on the order of 25 mM (150-152). In vitro studies indicated that Mn(II) formed a complex with lactate which possessed significant superoxide activity (153). These bacteria are additionally unable to produce heme and, consequently, when grown in the absence of heme, produce a hemeless catalase, or pseudocatalase (154-158). Unlike heme-containing catalases, the enzyme is not inhibited by cyanide or azide, and the addition of either Mn or Fe into the growth medium increased the amount of the pseudocatalase present. However, neither of the metals could be detected in partially purified enzyme assays (157). 

Prevents growth of aerobic organisms which can generate volatile acids and poor flavor... 

In general, the growth of an aerobic organism follows the equation... 

The value for Kk, the saturation coefiicient or growth-limiting substrate concentration at which organism growth rate is one-half its maximum value, varies considerably with the reaction, the species mediating the reaction, and environmental conditions. In anaerobic methane fermentations, Kk tends to be much larger, at least with acetate and propionate, than for aerobic oxidations. Values of 10" moles/liter seem appropriate for the former and 10" for the latter. Kk also tends to increase with decrease in temperature. 

The volume of media filled into the containers need not be the routine fill volume for the container. It should be of sufficient volume to contact the container-closure seal surfaces and sufficiently large to allow for easy inspection of the filled units postincubation. Despite the lower fill volume, the speed of filling should match that used for the routine filling of the product being simulated. Smaller containers should not be over-filled as sufficient air must be available in the container headspace to support the growth of aerobic organisms and problems have been encountered where the liquid media essentially fills the entire container. 

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