Water soluble, randomly substituted partial N-, partial O-acetylated chitosan, preserving compositions containing chitosan, and processes for making thereof

A pharmaceutical preserving composition comprising:

• (a) at least one chitosan or chitosan derivative selected from randomly substituted water soluble, partial N-, partial O-acetylated chitosan and glycol chitosan in an amount from about 500 to 1000 ppm;
• (b) at least one buffer solution selected from among a borate buffer and a phosphate buffer;
• and
• (c) at least one biocidal adjuvant selected from disodium ethylenediaminetetraacetic acid (EDTA), nitriloacetic acid, or ethyleneglycol-bis(β-amino-ethylether)-N,N,N′,N′-tetraacetic acid in an amount from about 150 to 500 ppm;
• wherein components (a), (b), and (c) are present in an amount such that the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli are reduced by at least 99.9% (3 logs) within 14 days following a 0 day challenge date and 14 days following a 14 day re-challenge date;
• and
• the growth of Aspergillus niger and Candida albicans is inhibited within 14 days following a 0 day challenge date and 14 days following a 14 day re-challenge date.