A study of highly efficient phenol biodegradation by a versatile Bacillus cereus ZWB3 on aerobic condition

−1·h−1. The concentration of phenol degraded by this strain was at a high level compared with reported ones, as shown in Rhodotorula sp. ZM1 (1,100 mg/L), Trichosporon cutaneum (1,250 mg/L), Rhodococcus sp. SKC (1,019 mg/L), Glutamicibacter nicotianae MSSRFPD35 (1,117 mg/L), Rhodococcus pyridinivorans PDB9T N-1 (1,600 mg/L), and so on (Duraisamy et al. 2020; Nouri et al. 2020; Wen et al. 2020; −1·h−1), Rhodococcus pyridinivorans PDB9T N-1 (28.6 mg·L−1·h−1), R. aetherivorans UCM Ac-603 (35.7 mg·L−1·h−1), Rhodococcus ruber C1 (47.5 mg·L−1·h−1), and so forth (Barik et al. 2021; Xu et al. 2021;

Figure 7

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Effects of initial concentrations under optimal conditions on (a) degradation of phenol and (b) growth of ZWB3 strain, respectively.

Figure 7

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Effects of initial concentrations under optimal conditions on (a) degradation of phenol and (b) growth of ZWB3 strain, respectively.

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Among various phenol treatment methods, microbial degradation is popular because of its features such as high removal rate, low cost, more complete degradation and no secondary pollution to the environment ( Li et al. 2020 ). The effect of initial phenol concentration on degradation by strain ZWB3 was explored under the optimal degradation conditions. At the concentration of 500 mg/L phenol, the lag phase for biodegradation was not observed, and phenol was completely degraded in 8 h, as shown in Figure 7 . When the concentration of phenol is 800 mg/L, 1,200 mg/L, 1,500 mg/L, lag phase was 2 h, 4 h, 8 h, respectively, and the corresponding completely degraded time was 13 h, 16 h, 26 h, respectively. In addition, at the concentration of phenol for 1,800 mg/L, the microorganism could not withstand the toxicity of phenol and led to microbial death, so the phenol could not be degraded. Herein, the maximum concentration of degradation for the isolated strain was 1,500 mg/L within 26 h, as the rate of 57.7 mg·L·h. The concentration of phenol degraded by this strain was at a high level compared with reported ones, as shown in Rhodotorula sp. ZM1 (1,100 mg/L), Trichosporon cutaneum (1,250 mg/L), Rhodococcus sp. SKC (1,019 mg/L), Glutamicibacter nicotianae MSSRFPD35 (1,117 mg/L), Rhodococcus pyridinivorans PDB9T N-1 (1,600 mg/L), and so on ( Su et al. 2019 Barik et al. 2021 ). The rate for degradation of phenol is higher than many other reported phenol-degrading strains, such as Acinetobacter lwoffii NL1 (41.7 mg·L·h), Rhodococcus pyridinivorans PDB9T N-1 (28.6 mg·L·h), R. aetherivorans UCM Ac-603 (35.7 mg·L·h), Rhodococcus ruber C1 (47.5 mg·L·h), and so forth ( Nogina et al. 2020 Zhao et al. 2021 ), demonstrating the highly efficient degradation ability of the isolated bacteria. With the increase of phenol concentration, the degraded time is increased. This phenomenon is due to the toxic effect of phenol on microorganisms. Therefore, a higher concentration of phenol results in that the cells take a longer time to adapt to phenol toxicity ( Paisio et al. 2013 ). In addition, high toxicity of phenol would inhibit the growth of cells, thus reducing the removal efficiency of pollutants ( Hussain et al. 2015 ). Otherwise, high concentration of phenol can further inhibit bacterial growth by reducing the expression of ATP synthase and inhibiting electron transport chain phosphorylation ( Geng & Lim 2007 ). Therefore, due to the toxic effect caused by phenol, initial concentration of phenol was a key factor for the complete removal of phenol.