Establishment of successive co-fermentation by Bacillus subtilis and Acetobacter pasteurianus for extracting chitin from shrimp shells

To simplify the process of chitin bio-extraction from shrimp shells powder (SSP), successive co-fermentation using Bacillus subtilis and Acetobacter pasteurianus was explored in this work. Among three protease-producer (B. licheniformis, B. subtilis, and B. cereus), only B. subtilis exhibited high compatibility with A. pasteurianus in co-culture. Successive co-fermentation was constructed as follows: deproteinization was performed for 3 d by culturing B. subtilis in the medium containing 50 g·L-1 SSP, 50 g·L-1 glucose, and 1 g·L-1 yeast extracts; After feeding 5 g·L-1 KH2PO4 and 6 % (v/v) ethanol, A. pasteurianus was cultured for another 2 d without replacing and re-sterilizing medium. Through 5 d of fermentation, the final deproteinization, demineralization efficiency, and chitin yield reached 94.5 %, 92.0 %, and 18.0 %, respectively. This purified chitin had lower molecular weight (12.8 kDa) and higher deacetylation degree (19.6 %) compared with commercial chitin (18.5 kDa, 6.7 %), and showed excellent structural characterization of FESEM and FT-IR analysis.