THE ISOLATION OF INDUSTRIALLY straints of the process. Bull et al. (1979) cited a number IMPORTANT MICRO-ORGANISMS of criteria as being important in the choice of organism:
The most publicized advances in biotechnology over the last ten years have been those in recombinant DNA technology. Whilst these advances have resulted in the development of extremely valuable new commercial processes and have improved many others, it is worthwhile reiterating Buckland's (1992) comment that the combined sales of four new microbial secondary metabolites introduced in the 1980s was greater than the sales of all the recombinant products added together. Thus, the diversity of micro-organisms may be exploited still by searching for strains from the natural environment able to produce products of commercial value. The first stage in the screening for microorganisms of potential industrial application is their isolation. Isolation involves obtaining either pure or mixed cultures followed by their assessment to determine which carry out the desired reaction or produce the desired product. In some cases it is possible to design the isolation procedure in such a way that the growth of producers is encouraged or that they may be recognized at the isolation stage, whereas in other cases organisms must be isolated and producers recognized at a subsequent stage. However, it should be remembered that the isolate must eventually carry out the process economically and therefore the selection of the culture to be used is a compromise between the productivity of the organism and the economic con-
1. The nutritional characteristics of the organism. It is frequently required that a process be carried out using a very cheap medium or a pre-de-termined one, e.g. the use of methanol as an energy source. These requirements may be met by the suitable design of the isolation medium.
2. The optimum temperature of the organism. The use of an organism having an optimum temperature above 40° considerably reduces the cooling costs of a large-scale fermentation and, therefore, the use of such a temperature in the isolation procedure may be beneficial.
3. The reaction of the organism with the equipment to be employed and the suitability of the organism to the type of process to be used.
4. The stability of the organism and its amenability to genetic manipulation.
5. The productivity of the organism, measured in its ability to convert substrate into product and to give a high yield of product per unit time.
Points 3, 4, and 6 would have to be assessed in detailed tests subsequent to isolation and the organism most well suited to an economic process chosen on the basis of these results. However, before the process may be
Principles of Fermentation Technology, 2nd Edn.
Table 3.1. Major culture collections
National Collection of Type Cultures (NCTC)
PHLS Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT, UK
National Collections of Industrial 23 St Machar Drive Ä£2ri'Ud- 1RY.UK
National Collection of Yeast Cultures (NCYC)
Collection of International Mycologieal Institute (IMI)
American Type Culture Collection (ATCC)
Deutsche Sammlung von Mikroorganismen und Zelkulturen (DSM)
Centraalbureau voor Schimmelcultures (CBS)
Czechoslovak Collection of Microorganisms (CCM)
Collection Nationale de Cultures de Microorganisms (CNCM)
Japan Collection of Microorganisms (JCM)
Culture Collection of the Institute for Fermentation (IFO)
AFRC Institute of Food Research, Norwich Laboratory, Colney Lane, Norwich NR4 7UA, UK
Culture Collection and Industrial Service Division, Ferry Lane, Kew,
Surrey TW9 3AF, UK
12301 Parklawn Drive, Rockville, MD 20852,' USA
Mascheroder Weg 1 b, D-3300 Braunschweig, Germany
P.O. Box 273, Oosterstraat 1, NL-3740 AG Baarn, Netherlands
Masaryk University, iostova 10, 662 43 Brno, Czech Republic
Institut Pasteur, 25, rue du Docteur Roux F-75724 Paris Cedex 15, France
Riken, Wako-shi, Saitama, 351-01 Japan
Institute for Fermentation,
Japan put into commercial operation the toxicity of the product and the organism has to be assessed.
The above account implies that cultm , ~ 3 isolated, in some way, from natural env J"*1 h< However, the industrial microbiologist mJ T'^ late' micro-organisms from culture collecUo,K ^% J and Doyle (1991) have provided a compre|lc collections and Table 3.1 cites some exan "f collections may provide organisms of known ,h Vh .st.es but may not contain those possessing desirable features, whereas the environment n™ m°st myriad of organisms, vety few of which mav h( a fory. It is certainly cheaper to buy a culL isolate from nature, but it is also true that ■ ' " organism may be found after an exhaustive searT'?' range of natural environments. The economic o f3 ations are discussed in more detail in Cha However, it is always worthwhile to purchase Z demonstrating the desired characteristics l*^ weakly, as they may be used as model ys develop culture and assay techniques which may be apphed to the assessment of natural isolates
The ideal isolation procedure commences witi, an environmental source (frequently soil) which is ', probable to be rich ,n the desired types, is so d as to favour the growth of those organisms pos the ndustnally important characteristic (i.e. The trially useful characteristic is used as a selective and incorporates a simple test to distinguish the mo desirable types. Selective pressure may be used isolation of organisms which will grow on par substrates, ,n the presence of certain compound under cultural conditions adverse to other types IU ever ,f lt ,s not possible to apply selective pressuic the desired character it may be possible to de procedure to select for a microbial taxon whidi known to show the characteristic at a relatively M frequency, e.g. the production of antibiotics by stre°p-tomycetes. Alternatively, the isolation procedure may be designed to exclude certain microbial 'weeds' and . encourage the growth of more novel types. Indeed,; pointed out by Bull (1992) for screening programmes to continue to generate new products it is becoming increasingly more important to concentrate on 1 known microbial taxa or to utilize veiy specific screening tests to identify the desired activity. During the iy«0s significant advances have been made in the establishment of taxonomic databases describing the properties of microbial groups and these databases have been used to predict the cultural conditions which would select for the growth of particular taxa. Thus, the advances m the taxonomic description of taxa have allowed the rational design of procedures for the isolation of strains which may have a high probability of
, Juctive or are representatives of unusual \ ad nin» identify productive strains amongst ninduciiw or arc represent» -, 1 I h • ul\ uices in pharmacology and molecular , enabled the design of more effective
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