Biosorption of organochlorine pesticides using fungal biomass AL Juhasz, E Smith, J Smith and R Naidu CSIRO Land and Water, PMB 2, Glen Osmond, South Australia, 5064, Australia Cladosporium strain AJR 3 18,501 was tested for its ability to sorb the organochlorine pesticide ( OCP ) p,p 0 - DDT from aqueous media. When p,p 0 - DDT was added to distilled water, ethanol or 1 - propanol solutions in excess of its solubility, p,p 0 - DDT was sorbed onto the fungal biomass. Increasing the amount of p,p 0 - DDT in solution by changing the medium composition increased sorbent uptake: p,p 0 - DDT uptake by the fungal biomass was 2.5 times greater in 25% 1-propanol (17 mg of p,p 0 -DDT g 1 dry weight fungal biomass ) than in distilled water. When p,p 0 -DDT was dissolved in 25% 1 - propanol ( 12 mg l 1 ), rapid p,p 0 - DDT sorption occurred during the first 60 min of incubation. p,p 0 - DDT in solution was reduced to 2.5 mg l 1 with the remaining p,p 0 - DDT recovered from the fungal biomass. A number of environmental parameters were tested to determine their effect on p,p 0 - DDT biosorption. As arsenic ( As ) is prevalent at DDT - contaminated cattle dip sites, its effect on p,p 0 - DDT uptake was determined. The presence of As [ As( III ) or As( V ) up to 50 mg l 1 ] did not inhibit p,p 0 - DDT uptake and neither As species could be sorbed by the fungal biomass. Changing the pH of the medium from pH 3 to 10 had a small effect on p,p 0 - DDT sorption at low pH indicating that an ion exchange process is not the major mechanism for p,p 0 - DDT sorption. Other mechanisms such as Van der Waals forces, chemical binding, hydrogen bonding or ligand exchange may be involved in p,p 0 - DDT uptake by Cladosporium strain AJR 3 18,501. Journal of Industrial Microbiology & Biotechnology (2002) 29, 163 – 169 doi:10.1038/sj.jim.7000280 Keywords: biosorption; Cladosporium; p,p 0 - DDT; organochlorine pesticide Introduction 1,1,1 - Trichloro - 2,2 - bis -( p - chlorophenyl )ethane (DDT) is an organochlorine pesticide ( OCP ) that was used extensively during the Second World War to control insect typhus and malaria vectors. After the war, DDT continued to be used as a residual spray for the eradication of malaria and as a delousing dust for typhus control as well as to control hundreds of insect pests associated with agricultural practices [ 17 ]. In 1972, DDT was banned from use in the United States due to the organochlorine exhibiting toxic effects towards nonpest invertebrates and the persistence of the compound in soils and aquatic sediments [6]. In addition, significant quantities of DDT were found to accumulate in various plant and animal tissues [ 7,8,24,25 ]. As a consequence, there were increasing concerns about the accumulation of the organochlorine in the food chain and the possible effects this may have on human health. In developed countries, the use of DDT was progressively restricted or phased out; however, DDT is still being used today in a number of developing countries. In tropical and subtropical regions of Australia, DDT was used extensively between 1957 and 1962 for the eradication of cattle and sheep ticks. As a consequence of the dipping and disposal practices, soil surrounding the dip sites was contaminated with DDT [ 5 ]. Although the use of DDT at cattle and sheep dip sites ceased almost 40 years ago, the pesticide still persists in these soils today [ 16 ]. In addition, these sites contain significant quantities of arsenic ( up to 3000 mg kg  1 ) [ 5,19 ] as a consequence of tick eradication methods prior to DDT use. The remediation of dip sites comes as a direct response to the encroachment of residential development close to old dip sites, which has raised many questions about the human safety factor. The remediation of DDT- contaminated soil has met with a number of problems. Physicochemical remediation processes, such as thermal destruction, may be used for soil cleanup; however, these techniques are prohibitively expensive. Bioremediation of DDT- contaminated soils has been unsuccessful due to the recalcitrant properties of the compound i.e., low aqueous solubility, high hydrophobicity, high degree of chlorination. When degradation does occur, DDT degradation rates are extremely slow and the resultant transformation products ( i.e., DDD and DDE ) are more toxic and recalcitrant than the parent compound [ 1,15 ]. Recently Juhasz and Smith [ 12 ] demonstrated the effectiveness of co - solvent washing on the desorption of DDT from contaminated soil. Co - solvents such as ethanol and 1 - propanol enhanced the solubility of DDT and remove the OCP from a number of soil types [ 12 ]. The combination of co - solvent washing and bio- sorption may offer an attractive alternative for the remediation of DDT- contaminated soils. Biosorption is a process where biological material is used to remove ( adsorb / absorb ) contaminants from waste streams. Bio- sorption has been used as an alternative technology for removing toxic heavy metals from waste effluents [ 23 ]; however, its use for removing organic contaminants from waste streams has received less attention. For the remediation of OCP - contaminated soil, the first step in the process would be to provide the contaminant in an available form for the biosorbent. This may involve a soil - washing process that utilises surfactants or co - solvents to solubilise the OCPs. The soil - wash solutions may then be passed through biological filters containing the biosorbent for the removal of the OCPs from solution. Biosorption offers many advantages over conventional remediation options. The process is rapid, has no nutritional requirements and DDT transformation products are not generated. In addition, a low operating cost is associated with the Correspondence: Dr Albert L Juhasz, CSIRO Land and Water, Private Mail Bag 2, Glen Osmond, SA 5064 Australia Received 15 January 2002; accepted 18 May 2002 Journal of Industrial Microbiology & Biotechnology (2002) 29, 163 – 169 D 2002 Nature Publishing Group All rights reserved 1367-5435/02 $25.00 www.nature.com / jim