Production of the enzyme dihydrofolate reductase by methotrexate-resistant bacteria isolated from soil

An overview of three biocatalysts of pharmaceutical importance synthesized by microbial cultures

This article includes a general overview of the published research on a topic relevant to biomedical sciences research, pharma-industries and healthcare sector. We have presented a concise information on three enzymes. These biomolecules have been investigated for their biocatalytic activities beneficial in the detection of drugs and their metabolites present in micro-quantities in samples of blood, urine, and other body fluids, such as salicylate hydroxylase, and dihydrofolate reductase. Some enzymes are useful in biotransformation of compounds to convert them in an optically active form, such as lipase. The information presented in this article has been collected from the published studies on their catalytic function, and biosynthesis using selected microorganisms. Several diagnostic assays are currently using enzymes as effective biocatalysts to perform the detection-test. For the marketing and consumer's convenience, pharmaceutical companies have designed biosensors and diagnostic kits by incorporating specific enzymes for rapid tests required in pathology, as well as for the quantification of certain metabolites and chemicals in pathology samples in a shorter time. For such purpose use of enzymes synthesized by selected specific microorganisms is economical.

Microbial enzymes with special characteristics for biotechnological applications

This article overviews the enzymes produced by microorganisms, which have been extensively studied worldwide for their isolation, purification and characterization of their specific properties. Researchers have isolated specific microorganisms from extreme sources under extreme culture conditions, with the objective that such isolated microbes would possess the capability to bio-synthesize special enzymes. Various Bio-industries require enzymes possessing special characteristics for their applications in processing of substrates and raw materials. The microbial enzymes act as bio-catalysts to perform reactions in bio-processes in an economical and environmentally-friendly way as opposed to the use of chemical catalysts. The special characteristics of enzymes are exploited for their commercial interest and industrial applications, which include: thermotolerance, thermophilic nature, tolerance to a varied range of pH, stability of enzyme activity over a range of temperature and pH, and other harsh reaction conditions. Such enzymes have proven their utility in bio-industries such as food, leather, textiles, animal feed, and in bio-conversions and bio-remediations.

Variations in antibiotic resistance profile in Enterobacteriaceae isolated from wild Australian mammals

We carried out a retrospective analysis of 946 strains of Enterobacteriaceae isolated from wild Australian mammals between 1993 and 1997. The prevalence of resistance to fixed concentrations of 32 antimicrobial agents was determined, and the respective roles that taxonomic family of the host, state of origin and bacterial species play in defining prevalence and range of resistance were investigated. Our results demonstrated a low but widespread prevalence of antimicrobial resistance in wild isolates. Only amikacin, ciprofloxacin, meropenem and gentamicin inhibited growth in all 946 samples. There was extensive variation in the combination of antibiotics to which isolates were resistant, and multiple antibiotic resistance was common. Geographical location and host group significantly influenced the antibiotic resistance profile of an isolate, whereas bacterial species influenced both the resistance profile of an isolate and the number of antibiotics it was resistant to. The role of these factors in determining observed antibiotic resistance profiles suggests that any study measuring resistance in wild isolates should include the broadest possible range of bacterial species, host species and sampling locations. As such, this study provides an important new baseline for future measurements of antibiotic resistance in the Australian environment.

Dihydrofolate reductase synthesis in continuous culture using a methotrexate-resistant Escherichia coli

A methotrexate-resistant strain of Escherichia coli Type I produced exceptionally high levels of the enzyme dihydrofolate reductase (EC 1.5.1.3) in 6 h of batch fermentation. The culture had markedly improved performance under chemostat culture conditions in terms of enzyme yield and output. Temperature, pH, dilution rates, and nutrient composition were optimized under chemostat culture conditions. A maximum enzyme yield of 10,360 U l-1 and a specific activity of 22.84 U mg-1 were obtained under chemostat conditions at pH 7.0, temperature 37 degrees C, and dilution rate 0.2 h-1, using media containing 1.0 and 0.6% (w/v) dextrose and yeast extract, respectively. The culture's performance and enzyme yields in chemostat and the feasibility of large-scale production are discussed.