Degradation of pesticides by the ligninolytic enzyme Laccase : optimisation of in vitro conditions, immobilisation and screening for natural mediators

Abstract: Pesticides are widely used in many industries but the majority reaches non-target organisms or locations through point or diffuse sources. Understanding conditions for their degradation is therefore important. The degradation of glyphosate, its metabolite AMPA and isoproturon using the ligninolytic enzyme laccase was studied. Optimisation of in vitro conditions were tested with findings indicating that factors such as altering pH and the concentrations of both manganese and redox mediators can impact degradation giving insight into optimal conditions. A method of encapsulation was used showing it is possible to immobilise laccase suggesting a possibility of its suitability as a co-formulation agent in pesticide applications. The immobilised laccase was applied in a laboratory scale experiment to investigate degradation of glyphosate and AMPA in soil and sand. The findings showed an apparent ability of the encapsulated laccase to be liberated and have an effect on glyphosate degradation, although much work still remains in this area. In the final part of this project ligninolytic substrates were screened for natural and easily extractable mediators. Extracts were used to check enzymatic activity and degradation potential. Candidates that showed promising results included extracts from hemp and wheat.