Extraction of Chitin with High Adsorption Capacity for Heavy Metal Ions from Shrimp Shells by Cofermentation of Bacillus altitudinis X-3 and Bacillus subtilis 01

Bacillus subtilis is often used to produce chitin from shrimp shells. Chitin is an aminopolysaccharide existing abundantly in shrimp shells that is a potential biosorbent, but the natural chitin has low adsorption capacity of heavy metal ions, which limits it as a biosorbent. In this work, the alkaline protease-producing strain along with Chitinase and chitin deacetylase X-3 identified as Bacillus altitudinis was isolated from soil near shrimp shell landfills, and then, a new synergistic fermentation system was established by cofermentation of Bacillus subtilis 01 and Bacillus altitudinis X-3 to produce chitin from shrimp shells (CBB). The obtained chitin was characterized by physiochemical properties, microstructure, and adsorption capacity of heavy metal ions. The results demonstrated that CBB had a high deproteinization efficiency of 97.17% and demineralization efficiency of 96.14%. Compared with chitin prepared by fermentation with Bacillus subtilis, the present chitin displayed a more hierarchically macro–micro porous structure, which caused excellent metal ions’ adsorption efficiency (Cu2+ of 94.93% and Pb2+ of 92.38%) and adsorption capacity (63.29 mg/g for Cu2+ and 61.59 mg/g for Pb2+). This approach provided a green, cheap, and efficient method to extract chitin from shrimp shells with increasing deproteinization efficiency and heavy metal ions’ adsorption efficiency, proving it to be a potential biosorbent.