Biotransformations of industrial use

Biotransformations represent a useful tool for the production of various chemical compounds because of their main advantages: attack of non-activated positions, regio, stereo and enantio-selectivity, and the mild reaction conditions. Organic chemistry can use these advantages in various enzymatic type reactions. One of the most interesting and promising groups of these biotransformations are the various oxidative reactions. The following article intends to give a short insight in the present state of this part of the broad field of biotransformations. Examples of technically interesting processes, preferably results of newer developments, should illustrate

• a the variety of enzymatical oxidative reactions used.
• b the various structures of educts for aimed oxidative modifications and.
• c the application in the pharmaceutical, food and chemical industries.

     

Enumeration of Enterobacter cloacae after chloramine exposure.

Growth of Enterobacter cloacae on various media was compared after disinfection. This was done to examine the effects of monochloramine and chlorine on the enumeration of coliforms. The media used were TLY (nonselective; 5.5% tryptic soy broth, 0.3% yeast extract, 1.0% lactose, and 1.5% Bacto-Agar), m-T7 (selective; developed to recover injured coliforms), m-Endo (selective; contains sodium sulfite), TLYS (TLY with sodium sulfite), and m-T7S (m-T7 with sodium sulfite). Sodium sulfite in any medium improved the recovery of chloramine-treated E. cloacae. However, sodium sulfite in TLYS and m-T7S did not significantly improve the detection of chlorine-treated E. cloacae, and m-Endo was the least effective medium for recovering chlorinated bacteria. Differences in recovery of chlorine- and chloramine-treated E. cloacae are consistent with mechanistic differences between the disinfectants.     

Severe hypoglycaemia due to combined use of parenteral nutrition and renal dialysis.

A 24-year-old woman who had sustained serious injuries in a road traffic accident required renal dialysis daily and was fed intravenously with a solution containing 25% dextrose. Subsequently insulin had to be added to the parenteral fluid to maintain blood glucose concentrations at physiological values. On one occasion parenteral feeding was continued until dialysis was started; she became comatose and the plasma glucose concentration was found to be less than 1 mmol/l (18 mg/100 ml). She responded rapidly to a 50 ml intravenous bolus of 50% dextrose. When parenteral feeding and dialysis are used simultaneously glucose passes across the semi-permeable membrane from the blood to the dialysate so that hypoglycaemia may occur. Insulin added to the parenteral fluid further decreases blood glucose concentrations. Stopping parenteral feeding 30-45 minutes before dialysis is started eliminates this danger of hypoglycaemia.     

Cell contamination due to the use of carrier-based microelectrodes

When using microelectrodes for intracellular ion activity studies, some uncertainties such as interference from cytosolic components at the microelectrode, cell damage, and cell contamination may arise. A model, which treats kinetic processes of the loss of carriers from the membrane phase of microelectrodes into the cytosol and cell membrane, is used for an estimation of the extent and time course of contamination by impaled ion-selective microelectrodes. An isolated model cell consisting of a plasma membrane surrounding a cytosolic milieu is assumed. The results of its considerations represent a worst case situation, in which significant contamination of the cell membrane of such a small isolated single cell might occur during time periods of electrophysiological experiments. In more complex situations, such as in intact tissues, the equilibrium membrane concentrations may be substantially less.     

Efficient use of DNA molecular markers to construct industrial yeast strains

Saccharomyces cerevisiae yeast strains exhibit a huge genotypic and phenotypic diversity. Breeding strategies taking advantage of these characteristics would contribute greatly to improving industrial yeasts. Here we mapped and introgressed chromosomal regions controlling industrial yeast properties, such as hydrogen sulphide production, phenolic off-flavor and a kinetic trait (lag phase duration). Two parent strains derived from industrial isolates used in winemaking and which exhibited significant quantitative differences in these traits were crossed and their progeny (50-170 clones) was analyzed for the segregation of these traits. Forty-eight segregants were genotyped at 2212 marker positions using DNA microarrays and one significant locus was mapped for each trait. To exploit these loci, an introgression approach was supervised by molecular markers monitoring using PCR/RFLP. Five successive backcrosses between an elite strain and appropriate segregants were sufficient to improve three trait values. Microarray-based genotyping confirmed that over 95% of the elite strain genome was recovered by this methodology. Moreover, karyotype patterns, mtDNA and tetrad analysis showed some genomic rearrangements during the introgression procedure.     

Iodination of zeta protein by lactoperoxidase. Chloroperoxidase and chloramine T.

Normal and Rous sarcoma virus transformed chicken embryo fibroblasts cultured on petri dishes were labeled with ¹²⁵I by two enzymic methods and one chemical method. The enzymic labeling systems employed chloroperoxidase and lactoperoxidase. Hydrogen peroxide was generated by glucose oxidase and glucose. The chemical method used chloramine T as the oxidant for iodide ion. After solubilization of cells, SDS disc gel electrophoresis and gamma counting, it was found that only one cell protein was predominantly labeled in all three reactions. This protein, a major cell surface protein, has been previously identified and termed Zeta protein. Zeta protein disappears from transformed cells and is susceptible to trypsin digestion.     

The frequency of consanguineous matings due to multiple use of donors in artificial insemination.

The amount of inadvertent inbreeding as a result of donor anonymity in artificial insemination has been estimated. A child from a first-cousin mating or closer is expected approximately once every 41/2 years in the United States as a result of artificial insemination by donor. Since a child with unknown paternity seems less likely to mate with paternal relatives than is a child with known paternity, artificial insemination by donor may actually reduce the average inbreeding of the population. Nevertheless, to reduce recessive diseases, inbreeding should be kept to a minimum by limiting the number of children produced by a single donor. Formulas are presented for local risks of inbreeding based on the number of children per donor.     

The use of temperature biofeedback in the treatment of chronic pain due to causalgia.

A patient with chronic pain due to a reflex sympathetic dystrophy in his hand and arm was successfully treated with temperature biofeedback after several months of conservative standard medical care brought little relief. Over the 18 treatment sessions the patient learned to emit a reliable handwarming response of 1 to 1.5 degrees C. Coincident with his learning, the pain in his hand and arm decreased markedly and remained absent at 1-year follow-up.