Efficiency surveys of the peracids Degaclean and Clarmarin in combination with the catalase inhibitor KH10 from the Degussa company for eradicating the two quarantine bacteria Clavibacter michiganensis ssp. sepedonicus and Ralstonia solanacearum in an aqueous suspension and in the sewage water of the starch industry.
The effect of the 2 newly developed peracids (the percarbonic acid Clarmarin and the peracetic acid Degaclean) from the Degussa company was tested using the 2 quarantine bacteria Ralstonia solanacearum and Clavibacter michiganensis subsp. sepedonicus. To obtain results for practical use, the sewage water of a starch company in Germany which contained soil and potato tuber debris was used. This population of microorganisms that naturally occur in the sewage water was chosen as the standard to evaluate the conventional bactericidal compounds in comparison with the peracids. It could be shown that the catalases of the microorganisms caused tremendous activity losses of the peracids. To inactivate these proteins, the application of a catalase inhibitor (KH10) was necessary, since the use of peracids alone required 20 000 ppm and a standard incubation time of 20 min. With the combination of Clarmarin/KH10 (1:1) at a concentration of 2000 ppm and the standard incubation time, the indigenous microbial population could be destroyed, whereas all other tested compounds, including the conventional hydrogen peroxide 'perhydrol' had only a small influence on the eradication rate. In laboratory-scale experiments only 100-200 ppm of the Clarmarin/KH10 mixture and an incubation time of 1-2 min was required to absolutely destroy a cell suspension of 109 cells/ml of the 2 quarantine bacteria, suspended in an aqueous solution (Ringer). This result shows that the possibility now exists to efficiently interrupt the infection cycle of quarantine bacteria if, for example, contaminated surface water is used for irrigating potato fields. In addition to the very fast reaction with organic compounds of the Clarmarin/KH10 mixture, there is a good environmental tolerance, since both peracids disintegrate into water, gaseous oxygen and easily degradable organic compounds. When adding R. solanacearum as a rifampicin-resistant isolate at a concentration of 109 cells/ml into the sewage water of the German starch company, the bacterium could be destroyed by applying a concentration of 1000 ppm of the Clarmarin/KH10 mixture for 20 min. By applying this small amount of the Clarmarin/KH10 mixture to the sewage water it has the advantage that not all indigenous microorganisms are destroyed, since they might be needed in the subsequent decomposition process of the sewage water.