Development of a practical method for inducing white-rot fungi to grow into and degrade organopollutants in soil

Abstract

White-rot fungi degrade many hazardous organic compounds that are not readily degraded by other microorganisms. Some of these compounds are soil contaminants, so methods for using these fungi to decontaminate soil through either land farming or composting technologies are being developed. White-rot fungi normally colonize plants or plant residues (e.g., wood) and do not grow well in unamended soil, particularly if it is not sterilized. A practical method to promote their growth in soil, without the use of large quantities of amendments or inoculum, is presented. A variety of assays showed that growth of white-rot fungi in steamed soil is limited by availability of carbon and nitrogen sources, but not other nutrients. Ground alfalfa straw was a more effective inexpensive source of these nutrients than the other amendments that were tested. However, the fungi only sometimes colonized alfalfa-amended nonsterile soil, as a result of competition from other microorganisms. Consistently high growth of the white-rot fungi in alfalfa-amended soil could be induced by adjusting the moisture content, adding the fungicide benomyl, and inoculating with benomyl-resistant fungi. In soil so treated, degradation (mineralization) of pentachlorophenol was much more rapid than in untreated soil.Key words: white-rot fungi, bioremediation, growth, pentachlorophenol.