Enhanced biodegradation of n-hexane in a two-phase partitioning bioreactor inoculated with Pseudomonas mendocina NX-1 under chitosan stimulation

Two-phase partitioning bioreactors (TPPBs) have been extensively used for volatile organic compounds (VOCs) removal. To date, most studies have focused on improving the mass transfer of gas phases/non-aqueous phases (NAPs)/aqueous phases, whereas the NAP/biological phases and gas/biological phases transfer has been neglected. Herein, chitosan was introduced into a TPPB to increase cell surface hydrophobicity (CSH) and improve the n-hexane mass transfer. The performance and stability of the TPPB with chitosan for n-hexane biodegradation were investigated, and it was found out that the TPPB with chitosan achieved maximum removal efficiency and elimination capacity of 80.6% and 26.5 g m- 3 h-1, thereby reaching much higher values than those obtained without chitosan (61.3% and 15.2 g m- 3 h-1). Chitosan not only obvio usly increased cell surface hydrophobicity and cell dry biomass on the surface of silicone oil, but might also allow hydrophobic cells in aqueous phases to directly capture and biodegrade n-hexane, resulting in an obvious improvement of mass transfer from the gas phase to biomass. Stability enhancement was another attractive advantage from chitosan addition. This study might provide a new strategy for the development of TPPB in the hydrophobic VOCs treatment.

Automated summary

This study introduced chitosan into a TPPB to increase cell surface hydrophobicity and improve n-hexane mass transfer, achieving higher removal efficiency and elimination capacity for n-hexane biodegradation compared to TPPBs without chitosan. Chitosan not only enhanced hydrophobic cells' ability to capture n-hexane in aqueous phases, but also improved mass transfer from gas phase to biomass, providing a new strategy for hydrophobic VOCs treatment in TPPBs.