Organizing the Enzyme Sources

There are advantages and disadvantages for each strategy. First, saving the clone banks as either DNA libraries or transformed pools provides the most flexibility and saves time and effort. The DNA can be transformed into any host that may be desired. Different hosts may be desired for different activities since 

One way of alleviating a number of these problems is actually to make several parallel clone banks using different expression vectors and strains, regulatable expression systems, and low copy-number vectors. Vectors choices [28] such as plasmids vs phagemids, high vs low copy number vectors, all can affect what is cloned, and there is not one solution which will satisfy every project. Furthermore, the cloning host also makes a difference. E. coli is usually the host of choice, but Bacillus can be preferred for secretable enzymes, and yeast for eukaryotic or post-transitionally modified enzymes. 

When a clean selection cannot be employed, one may perform an enrichment to increase the percentage of positive candidates in the screening pool by favoring growth of certain cells prior to the assay [22]. A number of resources exist to help design and develop screens and selections for different activities. LaRossa describes many selectable phenotypes that are available in 

While more difficult and time consuming to develop, petri-plate-based screens or 

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