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Hexaconazole biodegradation by a soil isolate and its dehydrogenase study

Volume No : Volume: 02 Issue : 9 Year : 2014 Page No: 491-496

Authors : Syed Rehan Ahmad and Abul Kalam

Abstract :

A microbiological assay of hexaconazole (a triazole fungicide) was standardized using a fungus, Fusarium oxisporum . No spontaneous decay of the fungicide was observed in aqueous solution. At high concentration only, certain amount of degradation was observed at 15  g/ml level after 12 days. A soil isolate of Penicillium frequentans HDF –1 was able to degrade the hexaconazole in culture even at 2000 g/ml level. The fungus was able to utilize fungicide as sole carbon source and to some extent total nitrogen source also. The culture filtrate containing fungicide (pretreated, 100  g/ml) was added during growth of P. frequentance with various ratios (1:9, 1:4, 3:7, 2:3 and 1:1) mixed with fresh culture medium and sterilized at 10 lb for 20 min. The final concentration remaining in the culture media were expected to be 100 g/ml a sterile culture medium containing fresh fungicide solution (i.e. 1, 2, 3, 5 and 10 g/ml) served as control. The sensitive fungus Fusarium was then inoculated in all experimental sets and incubated at 32 +2 0C for 16 days. It was observed that the Fusarium started to grow in medium containing culture filtrate up to 100 g/ml of fungicide whereas in control, no visual growth was observed from 5 g/ml onwards upto 8 days. Only faint growth was observed after 16 days at 10 ppm level. So, glucose dehydrogenase enzyme (GDH) was studied to test the differential effect on sensitive and resistant organisms. (E.coli HB 101) at 100g/ml concentration, whereas in sensitive organisms the enzyme was inhibited (43.5% in Fusarium and 90.2%, in B. subtilis respectively) When compared to control at the identical concentration of fungicide (100  g/ml).

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