Screening of Aromatic Hydrocarbons-degrading Bacteria and Production of PHA by an Improved Feeding Strategy

NI Yuyang; RHEE Youngha

doi:10.19672/j.cnki.1003-6504.2018.05.005

Abstract：Benzene, toluene, ethylbenzene, xylene (BTEX) are types of contaminants that are common and also very difficult to remove among volatile organic compounds. The method of utilizing microorganism to degrade BTEX and then converting into polyhydroxyalkanoate (PHA), has a double effect not only in pollutant disposing but also for recycling into environmental-friendly products. In this study, microorganisms capable of converting BTEX compounds to polyhydroxyalkanoate (PHA) were isolated from activated sludge by enrichment process. Among the isolates, three strains, identified as Pseudomonas fulva TY16, Pseudomonas putida MY21, and Pseudomonas fluorescence SX11, were selected for further study. These strains possessed different aromatic hydrocarbon-degrading genes and showed different degradation patterns towards BTEX compounds. The growth of strain TY16 was significantly decreased when the initial concentration of toluene in the medium exceeded 1.5 g/L. This problem could be successfully resolved by a novel continuous feeding system of gaseous aromatic substrates using a syringe pump. In fed-batch experiments, where toluene was constantly supplied to the fermentor at a defined flow rate, the growth of TY16 reached 3.8 g/L of dry cell weight (DCW) after 40 h of cultivation and the cellular content of accumulated PHA was 58％ of DCW. In this case, the conversion yield was 0.315 g/g, increasing about three times compared with 0.113 g/g obtained from a fermentation experiment with conventional airflow meter feeding system.