No abstract

Highlights The chitosan obtained shows physicochemical properties similar to commercials. The low molecular chitosan for harvesting microalgae shows better results than aluminum sulfate. The use chitosan for harvesting microalgae reduces the process costs.

The use of chitosan, a natural polymer, has recently increased due to its antimicrobial and antifungal character, null toxicity, biocompatibility and ability to form biofilms and hydrogels. The areas of application and research include biomedical, pharmaceutical, biomaterials, water treatment and haircare and skincare products. However, the applications of chitosan are limited due to the difficulty associated with modification of its structure and its poor solubility in water. Among the main chemical modifications for functionalising the chitosan structure are the N-substitution, O-substitution (with or without protecting the reactive sites of the chitosan) and cross-linking with other compounds; these chemical modifications allow improvement of its chemical and physical properties. In relation to the current importance of the use of chitosan with chemical modification, the present review attempts to explain in a simple way the main chemical reactions carried out with chitosan and its wide range of applications, and provides a future perspective.

The antibacterial effect of polyamide 6 ⁄ 66-chitosan blend and chitosan-coated plastic films was compared to chitosan films and chitosan solution, against Salmonella typhimurium and Staphylococcus aureus. The chitosan films did not show inhibition halos; however, contact inhibition was observed. During the tests, the films absorbed moisture, increasing of the diameter discs in relation to the concentration of the chitosan for both microorganisms at least 31%. Chitosan plastic film coating (bilayer system) showed only contact inhibition, without increase in contact area. The films from polyamide 6 ⁄ 66-chitosan blend had no antibacterial activity. The highest inhibitory effect resulted from a chitosan solution at 1000 and 2000 ppm for S. typhimurium and S. aureus, respectively. The results of this study showed that the antimicrobial activity was lessened when the chitosan was combined with the plastic matrix because of the absence of contact inhibition, and the best activity was obtained with films prepared by casting of chitosan solution.