Comparison of the physicochemical and structural characteristics of enzymatic produced chitin and commercial chitin

White shrimp (Litopenaeus vannamei) waste is a good source of chitin. However, the chemical chitin extraction generates a large amount of environmental-pollution and increases partial deacetylation of chitin. Therefore, the use of biological extraction is an interesting alternative. This study aimed to isolate chitin by Trypsin and Ficin with/without sodium-metabisulfite and investigate their properties as compared to commercial chitin. Shell demineralization and deproteinization were done by lactic-acid and proteolytic-enzyme (0.1-0.05%w/w). The enzymatic deproteinized shells were subjected to mild-alkali treatment (0-2% NaOH; 60 degrees C and 30 min). After demineralization the ash content was decreased to similar to 1.1%. The combination of enzymatic and mild chemical treatments exhibited the 92% deproteinization. The enzymatic deproteinization was higher in presence of sodium-metabisulphite (p > 0.05). The CI of enzymatic-chitin was more than commercial-chitin (p < 0.05). Therefore, a smooth with high molecular packing microstructure was observed in enzymatic- chitins. The DA% of enzymatic chitins (81-83%) were higher than chemical (p < 0.05). The chitins with DA between 70 and 90% and low protein content, is considered as good final products. Therefore, the enzyme-assisted chitin extraction generated the high grade chitin under mild and semi-ecofriendly conditions. This method is a promising alternative method for chemical extraction which can retain the native microstructure of chitin. (C) 2019 Elsevier B.V. All rights reserved.