Microbial physical entrapment

It is not clear if the types of interactions that dictate the behavior of tomato PGase are common to other PGase food systems. Certainly, one may expect that microbial PGases (e.g., those associated with rotting fruit) will have somewhat different associations with the food matrix. Enzyme-tissue ionic complexes are probably important in the case of exogenous microbial PGase, but physical entrapment probably is not. 

The death of a single microbial cell is a biochemical process (or series of processes) the entrapment of individual microbial cells in or on filters is due to physical forces. These effects on individual cells are peculiar to individual sterilization processes. On the other hand, the effects of inactivating processes and filtering processes on populations of microbial cells are sufficiently similar to be described by one general form—exponential death. Exponential kinetics are typical of first-order chemical reactions. For inactivation this can be attributed to cell death arising from some reaction that causes irreparable damage to a molecule or molecules essential for continuing viability. 

There are several physical mechanisms for the removal of cells and particles. These include sieving, adsorption, and trapping in the matrix. Membrane filters work mainly by sieving, whilst filters such as fibrous pads and sintered glass are depth filters, and work by adsorption and entrapment. Depth filters can suffer from microbial multiplication within the filter, which causes contamination in the filtrate, a problem known as grow through. 

Immobilized enzymes are defined as enzymes physically confined or localized in a certain defined region of space with retention of their catalytic activities, which can be used repeatedly and continuously. This definition is applicable to the enzymes as well as aU types of biocatalysts such as cellular organelles, microbial cells, plant cells, and animal cells. In some cases, these biocatalysts are bound to or within insoluble supporting materials (carriers) by chemical or physical binding. In other cases, biocatalysts are free, but confined to limited domains or spaces of supporting materials (entrapment). 

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