One-Step Biological Upcycling of Chitin Wastes into Violacein 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.