title: Protein extraction method for the proteomic study of a Mexican traditional fermented starchy food.
abstract: Pozol is a traditional fermented maize dough prepared in southeastern Mexico. Wide varieties of microorganisms have already been isolated from this spontaneously fermented product; and include fungi, yeasts, and lactic- and non-lactic acid bacteria. Pozol presents physicochemical features different from that of other food fermentation products, such as a high starch content, in addition to a low protein content. It is these qualities that make it intractable for protein recovery and characterization. The aim of this study was to develop a methodology to optimize the recovery of proteins from the pozol dough following fermentation, by reducing the complexity of the mixture prior to 2D-PAGE analysis and sequencing, to allow the characterization of the metaproteome of the dough. The proteome of 15day fermented maize dough was characterized; proteins were separated and analyzed by mass spectrometry (LC-MS/MS). Subsequent sequence homology database searching, identified numerous bacterial and fungi proteins; with a predominance of lactic acid bacterial proteins, mainly from the Lactobacillus genus. Fungi are mainly represented by Aspergillus. For dominant genera, the most prevalent proteins belong to carbohydrate metabolism and energy production, which suggest that at 15days of fermentation not only fungi but also bacteria are metabolically active.
  
  
  CONCLUSIONS
  Several methodologies have been employed to study pozol, with a specific focus toward the identification of the microbiota of this fermented maize dough, using both traditional cultivation techniques and culture independent molecular techniques. However to date, the dynamics of this complex fermentation is not well understood. With the purpose to gain further insight into the nature of the fermentation, we used proteomic technologies to identify the origin of proteins and enzymes that facilitate substrate utilization and ultimately the development of the microbiota and fermentation. In this paper we overcome the first general challenge for such studies, obtaining a protein sample with adequate quality capable of representing the system.
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Distrito Federal 04510, México; Programa de Posgrado en Ciencias Bioquímicas, Universidad Nacional Autónoma de México, Distrito Federal 04510, México.
authors.forename: C
authors.initials: C
authors.lastname: Cárdenas
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México.
authors.forename: B J
authors.initials: BJ
authors.lastname: Barkla
authors.affiliation: Facultad de Química, Universidad Nacional Autónoma de México, Distrito Federal 04510, México.
authors.forename: C
authors.initials: C
authors.lastname: Wacher
authors.affiliation: Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo 42086, México.
authors.forename: L
authors.initials: L
authors.lastname: Delgado-Olivares
authors.affiliation: Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Distrito Federal 04510, México. Electronic address: romina@biomedicas.unam.mx.
authors.forename: R
authors.initials: R
authors.lastname: Rodríguez-Sanoja
mesh_terms: D001230:Aspergillus / Q000737:chemistry; D002853:Chromatography, Liquid; D005285:Fermentation; D005504:Food Analysis / Q000379:methods*; D005516:Food Microbiology; D007778:Lactobacillus / Q000737:chemistry; D008800:Mexico; D064307:Microbiota; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification*; D020543:Proteome; D040901:Proteomics; D013213:Starch / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D014357:Trypsin / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry*
chemical_list: D011506:Proteins; D020543:Proteome; D013213:Starch; D014357:Trypsin
keywords: Metaproteome extraction method; Pozol; Proteomics of complex fermentations; Traditional food fermentation