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Germany: Biodegradable Crop Protection Ecologically Harmless Insect Repellent

| Editor: Alexander Stark

Conventional insecticides not only kill pests, they also endanger bees and other beneficial insects, as well as affecting biodiversity in soils, lakes, rivers and seas. A team from the Technical University of Munich (TUM) has now developed an alternative: A biodegradable agent that keeps pests at bay without poisoning them.

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If aphids have the choice between wheat seedlings with (right) and without CBT-ol treatment (left), they avoid the treated seedlings.
If aphids have the choice between wheat seedlings with (right) and without CBT-ol treatment (left), they avoid the treated seedlings.
(Source: W. Mischko / TUM)

Munich/Germany — Synthetically produced insecticides endanger not only bees but also beetles, butterflies and grasshoppers. They affect biodiversity in soils, lakes, rivers and seas. Their use has consequently been highly controversial for many years.

Professor Thomas Brück, who heads the Werner Siemens Chair of Synthetic Biotechnology at TU Munich, and his team have now found an alternative: The insect repellent they have developed is biodegradable and ecologically harmless. Sprayed on plants, it works much like mosquito repellent used by bathers in the summer, spreading a smell that keeps away unwanted insects. Instead of spraying poison, which inevitably also endangers useful species, their new approach deliberately merely aggravated the pests, Brück said.

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The Munich researchers were inspired by the tobacco plant, which produces cembratrienol in its leaves, CBTol for short. The plant uses this molecule to protect itself from pests.

Using synthetic biotechnology tools, Professor Brück's team isolated the sections of the tobacco plant genome responsible for the formation of the CBTol molecules. They then built these into the genome of coli bacteria. Fed with wheat bran, a by-product from grain mills, the genetically modified bacteria now produce the desired active agent.

According to Mirjana Minceva, Professor of Biothermodynamics at the TUM Weihenstephan Campus, the key challenge during production was to separate the active ingredients from the nutrient solution at the end of the process.

The solution was centrifugal separation chromatography: a highly efficient process that works equally well on an industrial scale, but hitherto, had never been used to separate products from fermentation processes.

Equally Effective against Bacteria

Initial investigations indicate that the CBTol spray is non-toxic to insects, yet still protects against aphids. Since it is biodegradable, it does not accumulate.

In addition, the bioactivity tests showed that cembratrienol has an antibacterial effect on gram-positive bacteria. It can thus be used as a disinfectant spray that acts specifically against pathogens such as Staphylococcus aureus (MRSA pathogen), Streptococcus pneumoniae (pneumonia pathogen) or Listeria monocytogenes (listeriosis pathogen).

Wolfgang Mischko, Max Hirte, Simon Roehrer, Hannes Engelhardt, Norbert Mehlmer, Mirjana Minceva and Thomas Brück; Modular Biomanufacturing for a Sustainable Production of Terpenoid-based Insect Deterrents; Green chemistry, May 14, 2018 – DOI: 10.1039/C8GC00434J

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