Kinetic Intensification of Interfacial Biodesulfurization via Self-Assembled Whole-Cell Pickering Emulsions

Biodesulfurization offers an energy-efficient alternative to conventional hydrodesulfurization, but its industrial efficiency is severely bottlenecked by the low bioaccessibility of hydrophobic substrates across the oil-water interface. Here, we addressed this mass-transfer challenge using exogenous-surfactant-free water-in-oil Pickering emulsions stabilized solely by Gordonia sp. WQ-01A cells. Exploiting the strain's native surface hydrophobicity (contact angle > 111°), the bacterial cells spontaneously assembled at the phase boundary to form a protective "bio-armor" without the aid of artificial barriers. Structural optimization indicated that an oil-to-water ratio of 1:4 and a cell loading of 10 g/L maximized the specific interfacial area with uniform droplets, governed by a limited coalescence mechanism that reached physical saturation at 20 g/L. Apparent kinetic modeling demonstrated a transition from a mass-transfer-limited regime to a pseudohomogeneous reaction regime, characterized by a significantly reduced apparent Michaelis constant Kmapp of 0.25 mmol/L and a maximum specific reaction rate Vmaxappof 9.96 mmol/kg-DCW/h. Consequently, the specific desulfurization rate was enhanced 3-fold to 5.17 mmol/kg-DCW/h compared to conventional aqueous systems, while maintaining over 90% activity across four consecutive 48-h cycles. This carrier-free strategy offers a practical, mechanically robust template for intensifying interfacial mass transfer in multiphase biocatalysis.