BIOSMAN

Insect pests can damage agricultural crops, consume and/or damage harvested food, in addition to diseases transition to humans and animals. Chemical insecticides and pesticides can affect human health directly or indirectly by disrupting ecological systems (air, rivers, lakes, oceans, streams, wetlands, forests and fields). At national and European levels, there is no regulation on the presence of pesticides in the air as it is the case for other pollutants typically. Since the early 1900s, Bacillus thuringiensis (Bt) bacterium group has received great attention, alternative to chemical products, for its use as an insect pest control agent, due to the parasporal inclusion production. The morphology of these inclusions may vary among Bt strains as bipyramidal, cuboidal, amorphous, spherical and irregular crystal morphologies can be observed. Previously it was believed to be important to end up with high spore counts. It was later shown that the spore count can give a good estimate of the growth of Bt in fermentation, but it does not always reflect the fermentation yield in terms of insecticide production since the amount of crystal protein, the main active compound, per bacterial cell can vary. Evaluation of these Bt products can be performed classically using several types of analysis ranging from bioassays to diverse biochemical methods. The main disadvantages of these methods are their expensiveness and their time-consuming character. Hence, an alternative physical method based on light scattering has been developed in order to quantify inclusion body formation and growth in recombinant cells. We recently showed that polarized speckle imaging method can be used to distinguish between Bt spherical crystal size and concentration within different fermentation products. In this project, we intend to extend our optical characterization, towards a real-time monitoring of the chemical fermentation reaction. Instead of embedding crystals into agarose gel to get rid of the Brownian motion, aqueous suspensions of crystals and/or spores will be studied; the reference Bt strains (HD1 and HD133) as well as isolated strains from Lebanese and Tunisian soil samples will be used. This project paves the way for potentially using laser polarized speckle at an industrial scale as a low-cost and non-invasive technique in order to characterize crystal geometry and to evaluate the yield of crystal production within fermentation. To achieve the objectives, the project gathers together experts in physics, chemistry and biology from three Mediterranean countries: France (UBO), Lebanon (USJ) and Tunisia (CBS).