Study On Biodegradation Of Hexachlorobenzene By White Rot Fungiin Liquid And Solid Cultur E Systems

Hexachlorbenzene (HCB), one of the twelve persistent organic pollutants (POPs), cancause cancer, malformation and mutation. Degradation of HCB is very difficult in naturalenvironment. Biodegradation of HCB by microbe was reported, especia lly the degrade dability of HCB by white rot fungi is strong, but it is not well researched. Degradation ofHCB by white rot fungi in liq uid and solid culture systems was studied in this paper.Two white rot fungi Pleurotus ostreatus and Trametes hirsuta were screened out fromfive white rot fungi for the high degradation of HCB. The optimization for degradationconditions of hexachlorobenzene (HCB) by Pleurotus ostreatus and Trametes hirsuta werestudied using Response Surface Methodology (RSM). The obtained optimum conditionsfor Pleurotus ostreatus and Trametes hirsuta were as follows: rotationa l speed of 153r/min, pH value of 8.0, temperature of 28℃, HCB concentration of 10mg/L, inoculationvolume of 5% (v/v) and culture time of 2 days; 128 r/min, inoculation volume of 7.5%(v/v), culture time of 2 days, HCB concentration of 10mg/L, temperature of 28℃andnatural pH. Under the optimized conditions, the ma ximum degradation rate of HCB byPleurotus ostreatus and Trametes hirsuta were 94.54% and 91.52% respectively, anddegradation speed were 4.724 mg/(L·d) and 4.578 mg/(L·d) respectively. Uniform electriccan increase the degradation rate of HCB by white rot fungi. Under the uniform electric of100 V·m-1 with standing culture, the degradation rate could reach 90.17%, while theexperimental group with no uniform electric the degradation rate is 52.93%. Under theuniform electric of 100 V·m-1 with no Trametes hirsuta inoculated the degradation rate was72.38%. The degraded products was analyzed using gas chromatography massspectrometry, the result showed that the main products were pentachlorophenols andpolychlorinated biphenyls.Comparison of the degradation rate of HCB for 20 days culture with addition of crudestraw and straw powder in solid culture system showed that the experimental group withaddition of crude straw was 24.46%, while the the experimental group with addition ofstraw powder was 14.16％.The degradation rate of HCB for 30 days culture with additionof Tween 80 mass fraction of 3% was 30.0%, which was 1.5 times of the experimentalgroup with no Tween 80 addition . Degradation rate of HCB of the experimental groupwith addition of Tween 80 concentration of 3% was almost equal to the one with addition of Tween 80 concentration of 1%. The optimization for degradation conditions ofhexachlorobenzene (HCB) by Trametes hirsuta in solid culture system was studied usingResponse Surface Methodology (RSM). The obtained optimum conditions were as follows :HCB concentration of 1.33 mg/g in the soil, addition of water of 4 mL of the crude straw,culture time of 4 days of the crude straw culture system, addition of crude straw of 2 g,temperature of 25℃, culture time of 10 days. Under the optimized conditions, thema ximum degradation rate and degradation speed of HCB could reach 31.6% and 41.08mg/(d·kg) respectively.