Application of extreme halophilic archaea as biocatalyst for chitin isolation from shrimp shell waste

Abstract

Halophilic archaea are known to have proteolytic activity and also has the capability to reduce ammonia from the processing discards. In this study, two proteolytic strains of halophilic archaea (Halobacterium salinarum and Halococcus dombrowskii) were evaluated for its deproteinization efficiency for isolating chitin. Fresh and cooked vannamei shrimp shell waste was fermented for a period of 16 days with regular samplings. Initial alkaline pH of the treatments had reduced drastically within 4 days and was maintained throughout the fermentation period. Total nitrogen and residual protein levels reduced gradually, while chitin nitrogen increased proportionally during the fermentation process due to proteolytic activity of haloarchaea. Total halophile count had increased over the fermentation period and maximum colony forming units (8.05 log CFU/mL) was found in T4. Among the two strains Halococcus dombrowskii, inoculated with cooked shell waste (T4) exhibited the highest proteolytic activity with 98% deproteinization. Correspondingly, 95% carotenoprotein removal was achieved by H. dombrowskii. As no demineralization was observed during the investigation period, the shell residue was further demineralized for chitin preparation. This study represents a novel, eco-friendly deproteinization technique of shrimp shell waste using halophilic archaea.