Degradation of p-nitrophenol and pentachlorophenol mixtures by Sphingomonas sp. UG30 in soil perfusion bioreactors

摘要

The degradation of mixtures of pentachlorophenol (PCP) and p-nitrophenol (PNP) were evaluated in pure cultures of Sphingomonas sp. UG30, statically incubated soils (60% water-holding capacity) and soil perfusion bioreactors where encapsulated cells of UG30 were used as a soil inoculant. In pure-culture studies, conditions were optimized for mineralization of PCP and PNP mixtures at concentrations of 30 mg l~(-1) each. Optimum in vitro mineralization of PCP and PNP mixtures by UG30 was facilitated using ammonium phosphate as a nitrogen source, while inhibition was observed with ammonium nitrate. The bioreactor system used columns containing soil treated with mixtures of 100, 225 or 500 mg kg~(-1) of PCP and PNP. Rapid dissipation of both substrates was observed at the 100 mg kg~(-1) level. Inoculation with UG30 enhanced PCP degradation at the 100 mg kg~(-1) level in bioreactors but not in static soil microcosms. At higher PCP and PNP concentrations (225 mg kg~(-1)), occasional complete degradation of PNP was observed, and PCP degradation was about 80% compared to about 25% in statically incubated soils after 20 days at 22 deg C. There was no additional degradation of the PCP and PNP mixtures attributable to inoculation with encapsulated cells of UG30 in either soil system at concentrations of 225 or 500 mg kg~(-1).