One-Step Biological Upcycling of Chitin Wastes into Violacein by Engineered <i>Chromobacterium violaceum</i>

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 <i>Chromobacterium violaceum</i> 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 <i>C. violaceum</i>, which demonstrated <i>cv_4240</i>, <i>cv_1440</i>, and <i>cv_2935</i> 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 <i>cv_4240</i>, <i>cv_1440</i>, <i>cv_2935</i>, and <i>vioABCDE,</i> 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.