Ultrasound-assisted conversion of alpha-chitin into chitosan.

This paper discusses the production of chitosan by applying high intensity ultrasound irradiation to alpha-chitin suspended in 40% aqueous sodium hydroxide. The average degree of acetylation (DA) of chitosan was determined by 1 H NMR spectroscopy and titrimetry while its viscosity average molecular weight (Mv) was calculated from the intrinsic viscosity as determined by capillary viscometry. The results show that fully acid-soluble chitosans (DA < 32%; 100,000 g/mol ⩽ Mv ⩽ 200,000 g/mol) are produced at very high yield (>95%) by applying non-isothermal ultrasound-assisted N -deacetylation process to alpha-chitin suspension (44 mg/mL). It is also shown that such a process is more efficient than thermochemical N -deacetylation, even being carried out at a lower temperature due to the effects of high intensity ultrasound irradiation. [ABSTRACT FROM AUTHOR]