Sorghum distillery residue (SDR) is a byproduct of Chinese liquor (baijiu) manufacturing, known for its high carbohydrate and nutrient content. This study utilized SDR as a growth medium and carrier to cultivate Aurantiochytrium sp. CJ6 for astaxanthin production. Through an isothermal torrefaction process, SDR was transformed into biochar (SDR-biochar), characterized by its rough surface and large cavities. Using SDR-biochar as a carrier for CJ6 cultivation effectively boosted cell growth and reduced CJ6 cultivation time. Continuous-feeding fed-batch (CF-FB) fermentation was employed to enhance astaxanthin synthesis. Without any carrier, a maximum astaxanthin concentration of 0.582 mg/L was achieved after 22 days of fermentation. However, when SDR-biochar was added as the carrier for CJ6 growth, a maximum astaxanthin concentration of 0.986 mg/L was reached within just 14 days. By combining CF-FB fermentation with the addition of SDR-biochar as the growth carrier, the astaxanthin productivity of CJ6 increased from 0.0264 mg/L/d to 0.070 mg/L/d, marking a remarkable 1.69-fold improvement.
