24. Microbial Chitinases: Natural Sources, Mutagenesis, and Directed Evolution to Obtain Thermophilic Counterparts

Chitin is the second most abundant polysaccharide, next to cellulose, occurring nature in the fungal cell walls, insect exoskeletons, while the shells of crustaceans contribute significantly to the availability of renewable biopolymer. Several enzymes are known to degrade different forms of chitin mostly produced by bacteria, fungi, and plants. Deacetylated polymer of chitosan and chitin is chemically hydrolyzed to generate oligomers and monomers for variety of applications that include pharmaceutical, environmental, agricultural, and cosmetic sectors. It would be possible to select from natural sources or modify the natural sources of chitinases to develop industrial processes that could replace the chemical processes for production of the chitooligomers, dimers, and monomers. Thermostable chitinases would give an added advantage for such industrial processes, and therefore there is a need to identify sources of such chitinases. In this chapter we have examined the availability of microbial sources of chitinases with a special attention to the thermostable chitinases. The approaches used in modifying chitinases and other related enzymes have been discussed to present the possible biotechnological approaches to generate novel thermostable enzymes. However, there was limited information available for chitinases indicating the need to focus research in that direction.