Research Topic: Characterization of rapeseed napin and potato patatin proteins expressed and produced from Pichia pastoris
Abstract: ** Lecture will be given in English**
Can plant proteins be produced without extracting them from the plant, while preserving the properties that make them useful food ingredients? Direct extraction is influenced by growth conditions, raw-material composition, and the presence of antinutritional compounds, while processing itself may alter protein properties. This study explores an alternative: recombinant plant protein production using Pichia pastoris under controlled fermentation conditions.
The work began with development of a fermentation platform. Different P. pastoris strains, carbon sources, and cultivation conditions were evaluated, reaching more than 240 g/L dry cell weight under optimized conditions. Ploidy was also examined using a fluorescent model protein, revealing higher recombinant protein production in diploid vs. haploid strains. The platform was then applied to two plant proteins: rapeseed napin and potato patatin. For napin, constitutive expression combined with a diploid strain resulted in approximately 8.8 g/L protein, whereas for patatin, methanol-induced expression was more effective for production of the secreted protein. A diploid advantage was also observed for patatin.
Following membrane-based concentration and purification, the recombinant proteins were compared with plant-derived counterparts. Recombinant napin showed a greater tendency to aggregate while retaining high emulsifying activity under acidic conditions. In patatin, the expression route affected both structure and function: the secreted protein was glycosylated and showed higher emulsifying activity, whereas the intracellular form formed gels at lower concentrations.
Finally, secreted patatin was evaluated for emulsifying, foaming, and gelation properties and incorporated into mayonnaise-type emulsions and gelatin-free gummies. Together, these results connect fermentation strategy with protein properties and, ultimately, with performance in food applications.
