A combination of lactic acid bacteria reduces the 33 mer peptide derived from α-gliadin.

CARLA L. GEREZ; GRACIELA FONT DE VALDEZ; GRACIELA ROLLÁN

Weihenstephan, Germany

Simposio; 4th International Symposium on Sourdough; 2009

Introduction. During wheat dough fermentation, gluten proteolysis by lactic acid bacteria (LAB) may hydrolyze certain immunologically active peptides, e.g. 31–43 (13 mer), 62–75 (14 mer) and 57–89 (33 mer) α-gliadin. However, the efficiency of degradation depends on the strain and the peptides involved. Previous results demonstrated that the 33 mer peptide was the most resistant to the hydrolysis by LAB due to its high content in proline residues within the sequence. The present study evaluates the complementation of different LAB peptidase activities as a tool for improving the 33 mer degradation. Methods. Thirteen LAB strains were evaluated for the hydrolysis of the synthetic peptide 33 mer by using cell-free extracts (CFE) in 20 mmol l-1 phosphate buffer (pH 7). The mixture was incubated at 37ºC for 24 h, at intervals (2h) the reaction was stopped by adding 0.1% (v/v) trifluoracetic acid. The resulting products were analyzed by RP-HPLC. The wheat doughs were prepared according to standardized elaboration protocols with a) the LAB mixture, ratio 1:1 and b) the mixture of CFE (ratio 1:1). Doughs prepared only with the commercial yeast were used as control. The concentration of gliadin was determined by using the Ridascreen® Gliadin Kit. Results. None of the LAB strains was able to hydrolyze the 33 mer peptide even after 24 h incubation. The study of the main specific peptidase activities allows formulating seven binomial mixtures of CFE (1:1 ratio). The only combinations giving positive results (12 and 32%, hydrolysis, respectively) after 4 h incubation were: L. plantarum CRL 775/L. curvatus CRL 760 and L. plantarum CRL 775/P. pentosaceus CRL 792. Lengthening the incubation time (8 h) improved the hydrolysis (56%) of the 33 mer peptide by the mixture L. plantarum CRL 775/P. pentosaceus CRL 792. No correlation between the individual peptidase activities (even proline-specific peptidases) and the capacity of the LAB strains to degrade the 33 mer peptide was observed. However, the supplementation of certain peptidase activities proline specific in the CFE combinations proved to be a competent tool for the peptide degradation. The efficiency of the best combination, L. plantarum CRL 775/P. pentosaceus CRL 792, was proved in dough fermentation. The supplemented doughs with BAL or CFE showed lower amounts of the gliadin, 70.3 and 82.7%, respectively, while this reduction was only 14.4% in the control after 24 h incubation. Conclusion. These results would be the start point for the development of novel starter cultures for bakery products.