Modeling of DBT biodegradation behaviors by resting cells of Gordonia sp. WQ-01 and its mutant in oil–water dispersions

Abstract

A strain of dibenzothiophene (DBT) biodegradation bacteria Gordonia sp. WQ-01 was subjected to He–Ne laser (632.8 nm) irradiation to improve the degradation ability. Under the optimum condition of output power of 20 mW for 15 min, a positive mutant strain WQ-01A was acquired. Intrinsic DBT biodegradation kinetics by resting cells of the wild strain WQ-01 and its mutant strain WQ-01A in aqueous phase was determined in shaking flasks. Batch DBT biodegradation experiments were carried out in a 7.5 L fermentor by the wild strain and its mutant strain in model oil system under different experimental conditions such as initial DBT concentration, resting cell density, and oil fraction (n-dodecane was used as the model oil because of its similarity to diesel oil). Furthermore, a mathematical model considering the intrinsic biodegradation kinetics and the overall oil–water mass transfer coefficient was developed to simulate the DBT biodegradation behaviors by resting cells of both strains in oil–water dispersions. The model calculations agreed well with the experimental results. Both theoretical simulation and experimental investigation indicated that the mutant strain had a much higher DBT biodegradation activity.