Hydrolyzes chitosan and chitooligosaccharides with retention of anomeric configuration. Has no activity against beta-D-galactoside, beta-D-glucuronide, beta-D-mannoside, chitin, glycol chitosan, cellulose, N,N'-diacetylchitibiose and pNP-GlcNAc. Hydrolysis of chitosan or chitosan oligosaccharides to remove successive D-glucosamine residues from the non-reducing termini. Optimum pH is 4.0. Stable between pH 6.0 and 9.0. Optimum temperature is 50 degrees Celsius. Stable below 50 degrees Celsius. Monomer. By growth on GlcN or GlcNAc. Belongs to the glycosyl hydrolase 2 family.