BACKGROUNDChemical chitin extraction generates large amounts of wastes and increases partial deacetylation of the product. Therefore, the use of biological methods for chitin extraction is an interesting alternative. The effects of process conditions on enzyme assisted extraction of chitin from shrimp shells in a systematic way were the focal points of this study. RESULTSDemineralisation conditions of 25 degrees C, 20 min, shells-lactic acid ratio of 1:1.1 w/w; and shells-acetic acid ratio of 1:1.2 w/w, the maximum demineralisation values were 98.64 and 97.57% for lactic and acetic acids, respectively. A total protein removal efficiency of 91.10% by protease from Streptomyces griseus with enzyme-substrate ratio 55 U g(-1), pH 7.0 and incubation time 3 h is obtained when the particle size range is 50-25 mu m, which was identified as the most critical factor. X-ray diffraction and C-13 NMR spectroscopy analysis showed that the lower percentage crystallinity and higher degree of acetylation of chitin from enzyme assisted extraction may exhibit better solubility properties and less depolymerisation in comparison with chitin from chemical extraction. CONCLUSIONThe present work investigates the effects of individual factors on process yields, and has shown that, if the particle size is properly controlled, a reaction time of 3 h is more than enough for deproteination by protease. Physicochemical analysis indicated that the enzyme assisted production of chitin seems appropriate to extract chitin, possibly retaining its native structure. (c) 2015 Society of Chemical Industry