Proteomic Analysis of Intra- and Extracellular Proteins of Aspergillus niveus during Submerged Bioprocess Culturing under Different pH Conditions

Abstract

Proteomics facilitates understanding of the complexity of molecular and physiological mechanisms involved in the metabolic and biological fungal adaptations to pH changes. Proteomics enables the identification of enzymes and fungal proteins involved in these adaptations. This approach may be used to investigate such fungi as Aspergillus niveus, whose proteome has not yet been analyzed, changes the intra- and extracellular protein profiles in response to extracellular pH. In the current study, we used two-dimensional gel electrophoresis (2DE) and mass spectrometry to evaluate the response of A. niveus to grow at pH 5, 6, 7, and 8 for 96 hours submerged bioprocess culturing. This study evaluated the response of A. niveus to grow at pH 5, 6, 7, and 8 for 96 h submerged bioprocess culturing, by analysis of two-dimensional gel electrophoresis (2DE), of the intracellular proteomes and the secretome, protein spots of interest were submitted to tryptic digestion and analyzed by matrix-assisted laser desorption/ionization time-offlight tandem mass spectrometry (MALDI-TOF/TOF-MS). This approach revealed substantial differences between the functions of intra- and extracellular proteins of A. niveus. The data suggested that pH-modulated global proteins are involved in important, mainly metabolic, processes, in the pentose phosphate pathway, protein regulation, cell wall maintenance, and others. Moreover, the change in extracellular pH could have altered the availability of nutrients, and induced the production of enzymes that respond to oxidative and other stresses. Proteomic facilitates understanding of the complexity of molecular and physiological mechanisms involved in the metabolic and biological adaptations of fungi to pH changes.