The influence of different modes of bioreactor operation on the efficiency of phenol degradation by Rhodococcus UKMP-5M

The performance of phenol degradation by Rhodococcus UKMP-5M in different modes of bioreactor operation, batch, and continuous, was studied. The effects of agitation and aeration on the growth and phenol degradation by Rhodococcus UKMP-5M were first studied in batch cultivation using a 2 L stirred tank bioreactor. Continuous bioreactor operation was design based on batch cultivation data and was operated at different dilution rates, ranging from 0.05 to 0.20 h(-1). The highest cell growth (0.262 g/L), phenol degradation time (12 h), and phenol hydroxylase enzyme (32.3 U/mL) in batch cultivation were obtained at the agitation speed of 160 rpm, DOT of 80 % saturation, and airflow rate of 1.5 vvm. In continuous operation, the highest steady-state cell concentration (0.03 g cell/L) and phenol degradation rate (0.082 g phenol/L/h) were achieved at the dilution rate of 0.18 h(-1). The efficiency of phenol degradation rate was about 3.28 times higher obtained in continuous cultivation (0.082 g phenol/L/h) than in batch cultivation (0.025 g phenol/L/h).