Green biorefinery of shrimp shell waste for α-chitin and high-value co-products through successive fermentation by co-lactic acid bacteria and proteolytic fungus

Abstract

Green biorefinery process was conducted to extract α-chitin and high-value co-products from shrimp shell waste through microbial fermentation using mature coconut water (MCW) as a sole nutrient source. Symbiotic co-lactic acid fermentation (Co-LAF) by Lactobacillus plantarum and Streptococcus thermophilus produced higher levels of lactic acid (LA) and protease activity than their mono-cultures, which led to greater demineralization (DM) and deproteinization (DP) of shrimp shell powder (SSP). After optimizing Co-LAF through Response Surface Methodology and successive fermentation by an acid-active proteolytic fungus Rhizopus oligosporus, the highest DM of 94.0 ± 0.91 % and DP of 86.7 ± 0.1 % were achieved. Based on FT-IR, XRD, and SEM analysis, the bio-extracted chitin had similar structural characteristics to commercial α-chitin but with better quality. These strategies not only contribute to environmentally-friendly and cost-effective extraction of α-chitin (303 ± 18 mg/g-SSP), but also co-produce LA (57.18 ± 0.89 g/L), acid protease (4.33 ± 0.5 U/mL), bio-calcium (277 ± 12 mg-CaSO4/g-SSP), protein hydrolysate (268 ± 5 mg/g-SSP), and pigments (28.78 ± 1.56 µg/g-SSP).