A microbial biorefinery for chitin and N-acetyl chitooligosaccharides from shrimp shell waste

Abstract

The global expansion of crustacean production has generated increasing volumes of chitinous waste, yet efficient recovery methods remain limited. Sustainable biorefinery approaches are urgently required to replace conventional chemical processes. This study proposes a microbial biorefinery strategy for comprehensive valorization of shrimp shell waste (SSW), focusing on the recovery of proteins, minerals, and chitin, as well as their conversion into value-added products. Three microbial strains were employed sequentially for deproteinization (DP), demineralization (DM), and chitin degradation. Strain GXUN-7 achieved a DP efficiency of 99.39%, yielding a hydrolysate enriched with free amino acids, 63.58% of which were essential. The hydrolysate exhibited a stimulatory effect on tobacco plant growth. Optimization of DM via orthogonal experimental design enabled GXUN-G1 to reach a 97.38% removal rate, with the resulting supernatant containing bioavailable calcium lactate suitable for plant nutrition. The recovered chitin exhibited a degree of acetylation of 88.93% and structural properties comparable to commercial chitin. The chitin-degrading strain GXUN-J6 produced hydrolysates with notable antioxidant activity, antimicrobial efficacy against Phytophthora nicotianae, and immunostimulatory effects, as evidenced by enhanced activities of superoxide dismutase, peroxidase, and phenylalanine ammonia-lyase. Operating under mild, non-corrosive, and energy-efficient conditions, the integrated bioprocess yielded ∼0.29 g of protein hydrolysate, ∼0.30 g of mineral supplement, ∼0.09 g of purified chitin, and ∼0.07 g of chitin hydrolysate per gram of SSW, demonstrating its environmental sustainability and economic viability. This eco-friendly, microbially driven biorefinery platform offers a promising and scalable solution for the circular utilization of shrimp shell waste.