One-Step Biological Upcycling of Chitin Wastes intoViolacein by Engineered Chromobacterium violaceum

Existing technologies for the valorization of organic wastes have been focused mainly on degradable wastes, while an efficient, low-carbon approach for the upcycling of shell waste is still lacking. Here, we report a one-step chitin biological fermentation process (CBFP), based on the construction of Chromobacterium violaceum engineered strain, for efficiently converting shell waste-derived chitin into high-value violacein. A high-efficiency CRISPR cytosine-base editor (pRK2-BE, 97% editing efficiency) was developed for C. violaceum, which demonstrated cv_4240, cv_1440, and cv_2935 as the major chitin hydrolysis genes and phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) as the major N-acetyl-glucosamine uptake pathway. The engineered strain WT/pBAD-4, co-overexpressing of cv_4240, cv_1440, cv_2935, and vioABCDE, efficiently utilized colloidal chitin and crystalline chitin as the sole carbon and nitrogen source, achieving violacein yields of 159.78 and 120.95 mg·L^–1, respectively. This study provided an economically viable and environmentally sustainable solution for green upcycling of shell waste.