Antibiotics economic importance

Microbially produced secondary metabolites are extremely important to our health and nutrition. As a group, they have tremendous economic importance. In the year 2007, the market for all anti-infective agents was 66 billion, and most of this was represented by 160 antibiotics and their derivatives. In 1929, Alexander Fleming published his historic observation that a contaminating mold, identified as PenicilUum notatum, killed his... 

Table II lists the fermentation products licensed in the U.S. for parenteral or topical administration to animals. Most of these are also used to treat human infections. As important as these are for animal health, of far greater economic importance are the antibiotics that are incorporated into animal feeds.

The world market for chemicals produced by fermentation methods is predicted to be about 44 billion by 2012, with more than half of that amount involving ethanol fermentation. A short list of economically important materials other than foodstuffe produced by fermentation methodologies includes bulk antibiotics, alcohols (ethanol, butanol, and so on), enzymes, organic acids (amino acids, citric acid, lactic acid, and others), vitamins, polymers, and biogums. 

Bleomycin and cyclosporine are the two economically most important streptomycete peptide antibiotics used as antitumor agents and immunomodulators, although dactinomycin is important medically for several tumors (see Chemotherapeutics, anticancer Immunotherapeutic agents). 

The choice of the strain of microorganism is one of the important variables in the process. The strains to be used in manufacture are mutants of the original producer, which are chosen as the result of a planned program of mutant selection. Sometimes a spontaneous mutation occurs usually, it is induced by mutagenic agents or irradiation of various sorts. The choice of the best strain depends on its abiUty to produce large amounts of the proper antibiotic in a reasonable time from ingredients that are economically feasible (73). 

Also illustrated in Figure 6.17 there is another important antibiotic, amoxicillin. Both amoxicillin and ampiciilin can be made enzymatically or chemically. Although enzymes are available that can be applied very well for the conversion of 6-APA into a variety of semi-synthetic penicillins, economic reasons are still impeding large scale applications. 

Despite much effort, antibiotic resistance continues to increase [61]. Looking back, it is clear that this was an inevitable consequence of antibiotic use [62], Antibiotic resistance, which has been recognized to be an important clinical problem, varies in prevalence from one country to another and among the pathogens themselves. This has great clinical, economic, political and environmental implications worldwide [63]. Strict adherence to the ongoing measures of infection control, education and antibiotic policy should minimize antibiotic resistance [64],... 

A technical process was developed by Lonza for the Ir-catalyzed hydrogenation of an intermediate of dextromethorphan (Fig. 34.9) which was carried out on a > 100-kg scale [70]. Important success factors were ligand fine tuning and the use of a biphasic system chemoselectivity with respect to C=C hydrogenation was high, but catalyst productivity rather low for an economical technical application. Satoh et al. reported up to 90% ee for the hydrogenation of an intermediate of the antibiotic levofloxacin using Ir-diphosphine complexes. Best results were obtained with bppm and a modified diop in the presence of bismuth iodide at low temperature [71]. 

No milk can be considered hormone free as natural hormones are always present. The question that has been under heated debate since approximately 1995 is whether the bovine somatotropin hormone (BST) injected into cows to increase milk production results in harmful levels of hormone in milk. The use of BST, which is based upon an economic return rather than any health benefit to the animal, raises two important questions what are the health risks to the human consumer, primarily children and what are the effects on the animals It is fairly well accepted that the use of BST increases the incidence of mastitis and therefore the potential for increased residues of antibiotic and antimicrobials in milk. Because of this Canada, Australia, Japan, the U.K., and other European Union countries decided that the health impact on animals was unacceptable and that BST was not to be used in their jurisdictions. Their decisions were not based upon any human health concerns, but strictly on concerns for animal health. 

The growing interest in various )5-lactam antibiotics, especially the cephalosporins, over the last decade has called upon improvement in their production methods via modification of either the basic process and the microbial strain or the downstream processing techniques. The product recovery may involve various methods of extraction and purification which play an important role in the overall process economics [12]. During recent years much attention has been given to the development of liquid membrane (LM) processes which usually exhibit high extraction rates and selectivity as compared to those achievable in conventional solvent extraction and adsorption processes. 

The complex structure of peplide antibiotics adds considerably to (he problems of synthesis, but more recent efforts toward improved peptide antibiotics are encouraging. Methods of hioassay and other laboratory use of economic antibiotics are available. Table 1 is a list of important peptide antibiotics. More extensive listings of minor peptide antibiotics have been published. 

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