Novel biotechnological route for the isolation and investigation of rhamnogalacturonan-I from apple side-streams as model systems

As much as 50% of the fruits and vegetables produced globally are wasted, and so are their valuable nutrients.

Fruit and vegetable waste mostly consists of primary plant cell walls, which are fibrous and recalcitrant composites of a load-bearing cellulose-cross-linking glycan network as being embedded in a more soluble matrix of polysaccharides, with pectin being the most abundant class of macromolecule within this matrix.

Crude pectin extracts are used for a variety of food applications.

While the functionality of pectin is sufficient for most current applications, the contribution of different pectic molecules, or structures within the same molecule, to its functionality is still poorly understood, as some structural elements are susceptible to degradation by common pectin extraction procedures.

Galactose, rhamnose and arabinose, which form the rhamnogalacturonan-I (RG-I) hairy region within pectin molecules, are acid-labile, explaining the extensive debranching during conventional extraction methods and the low amounts of RG-I in current pectic ingredients.

RHAPPLE aims to explore a novel biotechnological route for the selective isolation of intact RG-I from our designated model system apple pomace.

We will investigate the application of yeasts that have been genetically modified to secrete a set of enzymes degrading other plant cell wall polysaccharides.

We subsequently aim to provide the crucial knowledge on the structure-function relationships of RG-I and unlock its use as hydrocolloid, binding platform, and prebiotic. RHAPPLE is thus a cross-disciplinary project, involving microbiology, molecular biology and physico-chemistry tools.

Our fundamental research within precision fermentation will position RG-I as one of the most promising hydrocolloids and prebiotics in the food sector and will help to raise awareness for the loss of valuable compounds by wasting plant processing by- and co-products.