Comparison of use of immobilized cells and immobilized enzymes for bioanalysis: Considerations in determination of ethanol

Use of chemically modified PMMA microspheres for enzyme immobilization

Modified poly(methyl methacrylate) (PMMA) microspheres, about 7microm in diameter, carrying aldehyde groups on their surfaces were synthesized and used as the support for enzyme immobilization. The immobilizing behavior as well as the properties of immobilized enzyme was studied. The amount of bound enzyme can be extended to 76.8mg g(-1) support, which is relatively much higher than other supports. The kinetic investigation derived from three typical models shows that the practical process is more complicated than the ideal condition, with one or more interactions being involved in the immobilization process. The K(m) value is actually larger and V(max) is smaller in the immobilized form than those in the free form. The increased resistance of the immobilized enzyme against the changes of temperature indicates that immobilizing enzyme onto the modified microspheres is useful for enzyme immobilization.

Dietary alkyl thiol free radicals (RSS) can be as toxic as reactive oxygen species (ROS)

Harmful free-radicals, such as superoxide anion (a reactive oxygen species: ROS) are produced during aerobic respiration in all tissues because of only partial reduction of some oxygen molecules in mitochondria: this is due to one-electron reduction of each atom of oxygen, instead of four-electron reduction per molecule of oxygen to form water. Similarly, in liver, and many other tissues such as lung and brain, an electron transfer chain from NADPH to water occurs (with insertion of one oxygen atom into xenobiotic substrates) that uses cytochromes P450 (EC 1.14.14.1) as the electron acceptor. Here, futile recycling of electrons, in the absence of substrate produces the superoxide anion (*O2')--see above. Reactive oxygen species (ROS) and reactive sulfur species (RSS) may act in unison to damage biomolecules. For example, damage to biomolecules can occur by attack on phospholipid membranes, and also the targeting of DNA results in mutagenicity and associated carcinogenicity-related mutagenic damage. Free radical injury to low density lipoprotein (LDL) has been identified in the causation of atherosclerosis implicated in arterial disease, which can lead to heart attack and strokes.

Designer enzyme and cell applications in industry and in environmental monitoring

Renewed world interest in enzyme biotechnological industries now derives from the expectation that many new biocatalysts will be created by genetic engineering associated with protein engineering designer techniques, or by chemical modification of existing enzymes by use of protein tailoring methods. The biocatalysts produced are mainly enzymes, abzymes (catalytic antibodies) and synzymes (synthetic analogues or mimics), and these will be used in industry, synthesis, therapy: and in bioanalysis of components of foodstuffs, and the environment including water, air and soil. The biocatalysts, including whole cells, are firstly incorporated into a particular bioreactor form by use of enzyme engineering techniques such as immobilization, and are then used, as appropriate, to modify their substrates. Improved processing or enhanced products are thereby achieved in the case of manufacturing industry: or monitoring signals are generated, often in the form of a measurable change in current flow, in the case of environmental biosensors. Designer enzymes and cells can be made now for identified applications where the presently available biocatalysts are inadequate, incompatible or uncompetitive.