Preparation of highly purified chondroitin sulphate from skate (Raja clavata) cartilage by-products. Process optimization including a new procedure of alkaline hydroalcoholic hydrolysis

The aim of this study is to optimize the different stages for the obtaining of chondroitin sulphate from skate cartilage by means of experimental designs and kinetic approaches. The results of the hydrolysis cartilage using papain and an enzymatic preparation from ray pancreas are compared. Moreover, the basic differences among enzymatic and chemical hydrolysis are identified. In order to reduce the aggressive treatments with strong alkalis a combined step of hydrolysis–precipitation in hydroalcoholic solution is also proposed. Thus, the combination of enzymatic and chemical hydrolysis, selective precipitation together with membranes technology lead to the formulation of a quick and highly efficient process (15%, w/w) with low consumption of reagents and high purity for the chondroitin sulphate (I = 99%) obtained.