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FEATURE

Designing yeast derivative 2.0 to sustain aquaculture development

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by Stephane Ralite, Eric Leclercq, Sylvie Roquefeuil and Bruno Bertaud, Lallemand Animal Nutrition, France

east derivatives (inactivated whole yeasts, yeast extracts, yeast cell walls, etc…) are well known for their benefits in animal and human nutrition. They are particularly used to help balance the intestinal microflora and help stimulate the host natural defenses. Most yeast derivatives on the market today are by-products of the fermentation industry, such as biofuel production. They are usually characterised according to their biochemical composition: level of mannan-oligosaccharides

“Thanks to innovative yeast screening

strategy, a new generation of formulated yeast derivatives could be developed that shows promising results in helping aquatic species face stresses such as pathogen pressure, dietary challenge, or handling in a context of lower antibiotic usage "

(MOS), yeast β-glucans or protein contents. If such an approach is interesting to evaluate product purity, it does not totally reflect the functionality of the ingredients. As expert in yeast production, Lallemand Animal Nutrition has conducted a collaborative R&D program in partnership with renowned research institutes aiming at a better understanding of yeast fractions, in particular the relationship between composition and function. This research lead to the formulation of a new generation of yeast fractions with optimal characteristics in terms of pathogen binding, modulation of the immune system, as well as mucus production in fish. Such solutions are particularly

well adapted to answer the issues of aquaculture at a time of intensification and growing concern regarding the use of antibiotics. First trials conducted in fish and shrimp indicate very promising outcomes, in terms of animal performances and economic benefits for the producer.

Looking at yeast fraction at the molecular-level

Cutting-edge techniques such as atomic-force microscopy (AFM) and single-molecule force spectroscopy (SMFS) were used to study yeast fractions under a totally new light. These techniques represent powerful tools to investigate the forces associated with single molecules. The principle is to use a force sensor to measure the tension associated with a biopolymer immobilised on a surface (in this case, the yeast outer cell wall polysaccharides). The sensor is able to “read” through the surface of the sample (yeast fraction) and draw the topography of the binding forces (Figure 1, middle images).

Not all yeasts are equal

For the first time, we were able to “visualise” the yeast surface topography in terms of binding potential. It was shown that binding molecules were arranged differently depending on the yeast sample. For certain yeast strains, they are arranged as “sticky patches.” While in others, they are scattered along the surface. In terms of functionality, the sticky patches show higher adhesive properties. This finding clearly shows that, while biochemical parameters are important, they are not sufficient to account for the functionality of a given yeast fraction. The distribution of these molecules along the cell wall is also very important. These studies demonstrate that all yeast strains do not share the same biophysical structure, or topography. It was also shown that, for a given strain, binding properties can differ according to the production and inactivation process involved. Hence, for a given strain, it is essential to determine the optimal production conditions: fermentation, but also the

22 | April 2017 - International Aquafeed

APR 2017 - International Aquafeed magazine