Synchronous Degradation of Gliadin and Phytic acid by Potential Microbiota of Indigenously Fermented Sourdough and its Application in Wheat Dough Fermentation

Abstract

Foods containing high amounts of either phytic acid or gliadin can pose a risk for development of iron deficiency and celiac disease, respectively. Gluten intolerance is one of the food related disorders which is very common in Occidentals, but now it is also prevailing in Orientals. Wheat is the staple food of Pakistan and mainly consumed in form of Roti (flat bread) and Khamiri Roti /Nan (autochthonously fermented sourdough bread). Celiac disease and/or gluten sensitivity also poses irritable bowel syndrome (IBS) in human and other metabolic disorders and is mounting in Pakistani population. Recently, it has been reported that 20-30% of world is suffering from IBS, and gluten consumption is considered as the main triggering factor. In first phase, in total, sixty locally fermented sourdough samples were collected from various cities of Pakistan. Degree of gliadin degradation was determined by Fourier transform infrared spectroscopy (FT-IR), and gliadin degraded sample (D13) and nondegraded sample (D50) were selected based on agglomerative hierarchical clustering (Pearson correlation coefficient) and afterwards subjected to 16S rDNA gene-based sequence. Proteobacteria (50.65%) and Actinobacteria (6.70%) phyla were abundant as compared to Firmicutes (42.53%) in D13, while Firmicutes (83.44) were abundant in D50 than Proteobacteria (14.97 %). Lactobacillus genera was the core genera in D50 and D13, 52.13 and 33.73%, respectively. However, second most abundant genera in D50 and D13 was Weissella (27.15%) and Psychrobacter (21.53%), respectively. Shannon and Simpson indices indicated that D13 had comparatively more diversity to D50. The natural occurring complex bacterial community has potential to completely degrade gliadin. In second phase, gliadin degraded microbial strains were isolated from D13, and afterwards subjected to probiotic characteristics and phytic acid. Among seven gliadin-degrading bacterial strains, five were Enterococcus and two were Bacillus, while three gliadindegrading yeast strains were identified as Wickerhamomyces anomalus. Among all these strains E. mundtii QAUSD01 and W. anomalus QAUWA03 had revealed significant in vitro resistance, survival-ability, adhesion, and colonization in simulated gut conditions. These two strains had potential to synchronously degrade phytic acid and gliadin. These strains can be used in wheat dough fermentations. Finally, E. mundtii QAUSD01 and W. anomalus QAUWA03 were used, separately and consortia, in the fermentation of six commonly grown wheat cultivars of Pakistan (Lasani 2008, Seher 2006, Chakwal 97, Shafaq 2006, Bars 2009, Barani 83). Commercial baker’s yeast mediated fermentation and unfermented controls were also used for comparison. Gliadin and phytic acid degradation were determined by HPLC and GC-MS analysis, respectively. In addition, tight junction proteins, trans-epithelial resistance (TER) and ruffle formation in Caco-2 cells was evaluated. Phytic acid was completely degraded in all consortia fermented wheat cultivars, while maximum gliadin degradation was observed in consortia fermentation of Shafaq 2006. Relative to the other tested wheat cultivars, Lasani 2006 showed minimal toxic effects on Caco-2 cells in terms of ruffle formation, tight junction proteins and TER values. The breakdown of phytic acid and gliadin could lead to additional health benefits by enhancing minerals bio-availability.