Effects of Co-Fermentation with Lactic Acid Bacteria and Yeast on Gliadin Degradation in Whole-Wheat Sourdough

This study investigates the potential of utilising the proteolytic activity of two different strains, Levilactobacillus brevis FST140 and Pediococcus pentosaceus FST22, to assess their impact on wheat gluten proteins. A high-power ultrasound (US) treatment (850 kHz; 500 W/cm2; 35 °C) was used to activate the proteolytic system of LAB to promote gliadin-like protein degradation in wheat wholemeal-based sourdough. The proteolytic activity of L. brevis and P. pentosaceus increased two-fold with 10 and 20 min US stimulation, respectively, compared to fermentation without ultrasonication. Regarding the impact of proteolysis and sonication on gliadin proteins, fermentation with both strains reduced gliadin content in commercial gluten by an average of 77.4% compared to the untreated sample, and additional US treatment further enhanced gliadin degradation efficiency to an average of 83.5%. The combined application of US and lactic acid fermentation initiated a seven-fold decrease in wheat wholemeal flour (WF) gliadin levels compared to the untreated sample (47.2 mg/g). Furthermore, the synergistic application of US, LAB, and yeast fermentation allowed us to reduce gliadin content up to 1.6 mg/g, as well as to reduce gluten content in the sourdough up to 3 mg/g. Despite complete hydrolysis of the gliadin fraction under the combined effects of US and fermentation, glutenins were less affected by the applied treatments in all cases. The technology presented in this study offers a promising approach for producing gluten-free or low-gluten fermented products in the bread-making industry.