Compounds interactions during simultaneous biodegradation of hydrophobic n-hexane and hydrophilic methanol vapors in one- and two-liquid phase conditions

Simultaneous biodegradation of n-hexane (H) and methanol (M) was studied in batch culture in the concentration range of 5-10 g m(-3) and 1-5 g m(-3), respectively, in the absence and presence of 5-10 % v/v silicone oil. The addition of oil likely increased the mass transfer of H and ended up to H removal efficiency (REH) improvement from 72 -86 % to 92-94 %. In contrast, M removal efficiency (REM) decreased from 15-34 % to 6-24 %, due to an increase in the M partition coefficient from 0.00018 to 0.003. Based on statistical analysis, REH and REM of 90 % and 24 % were obtained at optimum condition of 5 g m(-3),1 g m(-3), and 5 % v/v for H, M, and oil fraction, respectively. Kinetic study based on Michaelis- Menten for H biodegradation showed that the presence of 5 % v/v oil could decrease the inhibition effect of the presence of M by increasing V-max from 123 to 133 mg (H) (g (biomass) d)(-1) and decreasing K-m from 21 to 17 g m(-3). Also, degree of mineralization increased from 27-29 % in the absence of oil to 35-43 % in the presence of oil for the identical experiments. According to 16S rDNA sequence analysis, Bacillus cereus and Pandoraea pnomenusa were identified as the main H and M degrading species, respectively, with REs >99 %. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The simultaneous biodegradation of n-hexane and methanol was studied in batch culture with the addition of silicone oil. The presence of oil improved the removal efficiency of n-hexane but decreased the removal efficiency of methanol. Statistical analysis and kinetic study provided insights into the optimal treatment conditions and reaction mechanisms for the biodegradation process.