Industrial enzymes strain improvement

This intractable problem may now be close to being solved. A Saccharomyces species that expressed the xylose isomerase gene from an anaerobic fungus was found to grow slowly on pentoses [29]. Improvement resulted from a combination of rational engineering - overexpression of the pentose phosphate-converting enzymes (see Fig. 8.5) - and classical strain improvement [30]. The authors conclude The kinetics of xylose fermentation are no longer a bottleneck in the industrial production of ethanol with yeast ... 

Rowlands RT (1984). Industrial strain improvement mutagenesis and random screening procedures. Enzyme Microb. Technol. 6 3-10. 

Above strategies for strain improvement and production process optimization may lead to reduction of the cost of enzymes to an extent however, downstream processing and product formulation for reasonably purified and highly stable enzymes are the key step toward success of any enzyme industry. 

For an industrial biotransformation, it is often necessary to further optimize an appropriate biocatalyst. This includes the elimination of the follow-up enzymes in the wild-type strain by mutations and the improvement of other characteristics by additional mutations and the selection of improved strains. Alternatively, the genetic information for a desired enzyme might be introduced in a host that has many of the preceding characteristics, and that has no enzymes that could modify or degrade the desired product. 

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