Generation and stabilization of CO 2 nanobubbles using surfactants for extraction of polyphenols from Camellia oleifera shells.

Camellia oleifera shells are abundant in polyphenolic compounds. Green extraction methods of polyphenolic compounds are essential to ensure product quality, efficiency, process cost, environment, and safety. This study investigated the effect of Tween 80 and Rhamnolipid surfactants on the production and utilization of stabilized carbon dioxide nanobubbles (CO 2 -NBs). The results confirmed the presence of the CO 2 -NBs in ultra-pure water with a concentration of 8.45 ± 1.05 × 10 8  ml -1 , among which the stable CO 2 -NBs possessed a mean size of 40-90 nm and a negative zeta potential (-41.6 ± 1.3 mV). Further, the efficiency of CO 2 -NBs combined with ultrasonication (CO 2 -NBs-Rh-UAE) was evaluated to extract polyphenols from Camellia oleifera shells (waste). The CO 2 -NBs treatment with ultrasonication showed the highest total phenolic content (TPC) and total flavonoid content (TFC) (36.75 ± 0.22 mg GAE/g DW and 24.06 ± 0.22 mg RE/g DW, respectively). Overall, this study demonstrated an innovative approach for producing, stabilizing, and utilizing biosurfactant stabilized CO 2 -NBs to extract polyphenolic compounds from the waste agricultural products. These findings highlighted the potential application of biosurfactant-stabilized CO 2 -NBs.