Dear Sir. Concerning your issue about the best method for chitosan extraction. Preparation of chitosan from samples was performed using the general method comprising of demineralisation, decolourisation and deacetylation. Raw samples were washed thoroughly with water, dried in oven and soaked in 1% HCL solution for 36 hours. It was then washed dried in oven and kept in 2N NaOH solution for 36 hours for demineralisation. samples were then kept in Potassium permanganate solution (having composition 1g of KMnO4 in 100ml water) for 1 hour, followed by keeping it in Oxalic acid (having composition 1g of Oxalic acid in 100ml water) for the process of decolourization of the experimental sample. These processes resulted in chitin as the product which was further treated with 50% w/v NaOH for the process of deacetylation resulting in chitosan as the end product. I think the following below links and the attached file may help you in your analysis:
You can refer to Dr. Jalal Al-Noor in our department (Fisheries) since about half of his PhD dissertation work was on marine chitosan extraction, characterization and application.