Fate of the Cry1Ab protein from Bt-maize MON810 silage in biogas production facilities

Biogas plants fuelled with renewable sources of energy are a sustainable means for power generation. In areas with high infestation levels with the European corn borer, Ostrinia nubilalis (Hbn.), it is likely that transgenic Bt-maize will be fed into agricultural biogas plants. The fate of the entomotoxic protein Cry1Ab from MON810 maize was therefore investigated in silage and biogas production-related materials in the utilization chains of two farm-scale biogas plants. The Cry1Ab content in silage exhibited no clear-cut pattern of decrease over the experimental time of 4 months. Mean content for silage was 1878 +/- 713 ng Cry1Ab g(-1). After fermentation in the biogas plants, the Cry1Ab content declined to trace amounts of around 3.5 ng g(-1) in the effluents. The limit of detection of the employed ELISA test corresponded to 0.75 ng Cry1Ab g(-1) sample material. Assays with larvae of O. nubilalis showed no bioactivity of the reactor effluents. The utilization of this residual material as fertilizer in agriculture is therefore deemed to be ecotoxicologically harmless.