Optimization of Feeding Strategy in Fed-Batch Cultures for Degradation of Phenol by Trichosporon sp.X1

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Fed-batch cultures were carried out for the degradation of phenol by Trichosporon sp.X1. When phenol was used as the sole carbon and energy source, the suitable phenol concentration was studied to avoid the substrate inhibition. Exponential feeding strategy with manual feedback was adopted to obtain higher cell concentration. The optimal set point of specific growth rate was 0.4~0.5μmax (μmax denotes the maximum specific growth rate from Haldane model). The exponential feeding strategy with optimal substrate concentration (110mg/L) was found to be more efficient since higher specific growth rate was stimulated by residual phenol. phenol and basal salt (BS) medium (NaH2PO4, 0.3gL -1 ; Na2HPO4, 0.7gL -1 ; KCl, 0.1gL -1 ; NH4NO3, 1.0gL -1 ; MgSO4, 0.1gL -1 ; CaCl2, 0.1gL -1 ; FeSO4, 0.01gL -1 ; pH 6.8±0.2) for flask cultures at 32℃ with shaking at 150 rpm for 12h. After centrifugation for 5min at 800×g, the supernatant was discarded and sedimented cells were freshly dissolved in 10mL phosphate buffer saline. This cell slurry was then inoculated into a 1L fed-batch reactor. The medium in the reactor contained BS medium and 100mgL -1 phenol as the sole carbon and energy source.