A systematic review of physical techniques for chitosan degradation

Chitosan is a biomaterial that has widespread applications in different fields such as food industry, agriculture, pharmacy, medicine, cosmetology, textile and paper industries etc. These diverse applications have necessitated the development of novel technologies for processing of chitin into chitosan and its low molecular weight derivatives, with the latter exhibiting a better aqueous solubility as compared to the parent polymer. Various chemical, physical and enzymatic methods have been explored to date for degradation of chitosan. However, insufficient process controls along with ever increasing environmental concerns demand efficient utilization of chemical reagents and catalysts utilized for chitosan processing. The physical methods of chitosan degradation therefore provide a viable means of generating chitosan oligomers. This manuscript attempts to extensively review these various techniques. Further, the manuscript provides a comprehensive overview of the procedures and principles that are critical for the processing of chitosan using different physical techniques like plasma treatment, milling, hydrodynamic cavitation, sonication, homogenization, photo-radiation etc.