# Enhanced Methyl _Tert_-Butyl Ether Removal by Mixed Consortium: Performance and Adaptability
## 3 Result and Discussion
### The Mixture of Three Pure Cultures Enhanced the Removal of MTBE

Table 1: The kinetic parameters corresponding to the degradation curve by a mixed consortium at various concentrations. \begin{table}
\begin{tabular}{c c c c} \hline
**Type of Bacteria** & **L1** & **M3** & **M10** \\ \hline First-order model & & & \\ S\({}_{0}\) (mg/L) & 10.24 \(\pm\) 0.39 & 10.78 \(\pm\) 0.48 & 10.41 \(\pm\) 0.50 \\ k (mg/L-h) & 0.020 \(\pm\) 0.002 & 0.021 \(\pm\) 0.002 & 0.019 \(\pm\) 0.002 \\ R\({}^{2}\) & 0.9778 & 0.9716 & 0.9634 \\ Quiroga-Sales-Romero model & & & \\ S\({}_{0}\) (mg/L) & 9.69 \(\pm\) 0.39 & 10.03 \(\pm\) 0.24 & 9.75 \(\pm\) 0.47 \\ q (mg/L) & 0.71 \(\pm\) 1.10 & 1.15 \(\pm\) 0.40 & 0.49 \(\pm\) 1.68 \\ \(\mu_{\text{max}}\) (h\({}^{-1}\)) & 0.04 \(\pm\) 0.02 & 0.06 \(\pm\) 0.01 & 0.04 \(\pm\) 0.02 \\ R\({}^{2}\) & 0.9897 & 0.9963 & 0.9838 \\ Boltzmann model & & & \\ A\({}_{1}\)(mg/L) & 12.43 \(\pm\) 3.38 & 11.24 \(\pm\) 0.88 & 11.80 \(\pm\) 3.15 \\ x\({}_{0}\) (h) & 26.38 \(\pm\) 11.77 & 31.73 \(\pm\) 3.19 & 33.82 \(\pm\) 10.70 \\ R\({}^{2}\) & 0.9897 & 0.9963 & 0.9838 \\ \hline \end{tabular}
\end{table} 
Table 2: The kinetic parameters corresponding to the degradation curve by pure strains at 10 mg/L. The Mixture of Three Pure Cultures Effectively Removed MTBE in the Co-Occurrence of Other Gasoline Components  
Currently, most researches have focused on the degradation of target pollutants, but the effect of coexistent pollutants are neglected. MTBE is always detected in the environment together with other gasoline components, such as alkanes, BTEX, and heavy metals [34]. Therefore, it is important to explore the interaction between MTBE and other organics or metals to stimulate the in situ bioremediation of MTBE. The individual and simultaneous removal of MTBE with other gasoline organic components is shown in Figure 3a, and the highest degradation efficiency was achieved by adding MTBE alone. In binary mixtures with BTEX, the degradation efficiency of MTBE was 5-10% lower, with a greater negative impact on the M10 strain. Furthermore, dodecane was unfavourable to MTBE removal with a 35-50% reduction of degradation efficiency, and M3 strain was more susceptible to dodecane. The addition of both alkanes and BTEX led to a reduction in MTBE biodegradation, and the effect of each substrate on MTBE removal decreased in the order of dodecane > BTEX. The significant differences in degradation efficiency of the experimental groups containing different carbon sources were verified by ANOVA (\(p<0.01\)). One of the possible reasons was that three strains used in this study could utilize dodecane and BTEX as the carbon source for growth (Figure S1). Compounds with a higher affinity for bacteria were found to compete with MTBE for the action of enzymes to reduce the MTBE removal [35]. Moreover, it can be speculated that strains preferentially metabolized aliphatic hydrocarbons rather than ethers, which is consistent with previous studies. Since other studies have mainly focused on the effect of BTEX on MTBE removal, a system containing multiple substrates was proposed in this study. In ternary mixtures, the degradation efficiency of MTBE was lower than adding BTEX alone, but slightly higher than mixing with dodecane. This may be due to the synergistic effect provided by the mixing of alkanes and aromatics. It was reported that both hydroxylase genes related to the alkanes and dioxygenase genes related to the biodegradation of aromatic hydrocarbons were detected simultaneously in the mixture system [36]. What is more, the results illustrated that the degradation efficiency of MTBE was improved by about 10% with the mixed consortium compared with pure strains in the ternary system. In particular, the mixed consortium promoted MTBE removal in either binary or ternary mixtures containing dodecane. Some researchers support the cultivation of a mixed consortium for the bioremediation in the co-occurrence of other pollutants. [PERSON] et al.