Crude chitosan was prepared from shrimp shell by HCl, NaOH and ethanol solution successively. Hydrogen
peroxide was used to degrade the crude chitosan into water-soluble chitosan. A mathematical model
between degradation conditions (H2O2 level, time and temperature) and the recovery of water-soluble
chitosan was constructed using response surface methodology. Each factor showed a significant effect on the
recovery. The model was confirmed to have a good fitness by analysis of variance. The optimal conditions to
obtain the highest recovery of water-soluble chitosan were 5.5% of H2O2 level, 3.5 h of time and 42.8 °C of
temperature. The predicted recovery was 93.5%. Through testing the number of colony, both crude and
water-soluble chitosan showed good inhibition activities against B. subtilis. By determination of inhibition
zone diameter, water-soluble chitosan showed significantly (Pb0.05) higher inhibition capabilities against E.
coli, B. subtilis and S. aureus than crude chitosan.
Industrial relevance: Chitin is the second abundant polymer next to cellulose over the world. Its deacetylated
product, chitosan, is an important ingredient in medicine and food. However, the low solubility in water
limits the application of chitosan. In this work, the chitosan was degraded by H2O2 to produce water-soluble
chitosan. Response surface methodology was taken to construct a model between degradation conditions
and the recovery of water-soluble chitosan. By determination of the antibacterial activity, water-soluble
chitosan showed better antibacterial activity than crude chitosan without degradation treatment. The results
indicated the high potential of water-soluble chitosan as an antibacterial agent. This work was helpful for
applying this product in industry.