Biodegradation of free-gossypol by a new fungus isolated from cotton planted soil

A new fungal strain isolated from a soil microcosm was investigated due to the finding that it could biodegrade free-gossypol on agar plates. Benzyl chloride was used for extracting fungal genomic DNA which was isolated from mycelium grown in liquid culture, then 18S rDNA was specifically polymerase chain reaction (PCR) amplified using a pair of primers EF4/EF3 (1.4 kb). The strain was further identified as a member of the genus Aspergillusthrough the morphological and molecular biological methods. The isolated strain had a high tolerance of free-gossypol and 2 g/L was chosen as the best addition amount. Furthermore, the dry weight method was employed to determine the growth curve and optimum temperature of the gossypol-degrading fungus in different carbon sources. The results showed that it was best to be researched after incubation for 72 h at 30°C. To the extent of our knowledge, this is the first report on biodegradation of gossypol on solid plates without other carbon sources and this might help in decomposing some anti-nutritional factors in feed resources.   Key words: Free-gossypol, fungus, biodegradation, isolation, growth characteristics.