Isolation involves obtaining either pure or mixed culture followed by their assessment to determine which carry out the desired reaction or produce the desired product. It is also possible to design the isolation procedure in such a way that the growth of producers is encouraged or that they may by recognized at, the isolation stage, whereas in other cases organisms may be isolated and producers recognized at a subsequent stage.
The ideal isolation procedure commences with an environmental source (frequently soil) which is highly rich in the desired nutrients. Isolation procedures may be designed to exclude certain microbial weeds and to encourage the growth of more novel types.
The isolation of a suitable organism for a commercial process may be long and very expensive procedure and it is therefore essential that it retains the desirable characteristics that led to its selection. Preservation techniques have been developed to maintain cultures in a state of suspended animation by storing either at reduced temperature or in a dehydrated form.
a) Storage at reduced temperature
i) Storage on agar slopes.
ii) Storage under liquid nitrogen.
b) Storage in a dehydrated form.
i) Dried cultures.
The process of strain improvement involves the continual genetic modification of the culture, followed by reappraisals of its culture requirements. Genetic modifications may be achieved by selecting natural variants, by selecting induced mutants’ and by selecting recombinants.