Proteome responses to nitrate in bioethanol production contaminant Dekkera bruxellensis

Dekkera bruxellensis is an industrially relevant yeast, especially in bioethanol production. The capacity of D. bruxellensis to assimilate nitrate can confer advantages of this yeast over Saccharomyces cerevisiae at industrial conditions. In the present work we present the consequences of nitrate assimilation, using ammonium as reference, to the proteomics of D. bruxellensis. Thirty-four protein spots were overproduced in nitrate medium and were identified by MS-TOF/TOF analysis and were putatively identified by using local Mascot software. Apart from the overexpression of genes of nitrate metabolism, ATP synthesis and PPP and TCA pathways previously reported, cultivation on nitrate induced overproduction of glycolytic enzymes, which corroborate the high energy demand and NADH availability for nitrate assimilation. Overproduction of alcohol dehydrogenase (Adh) protein was also observed. Proteomic profile of D. bruxellensis cultivated in nitrate and described in the present work agrees with the hypothesis of metabolic flux regulation, making available the energy in the form of NADH to support nitrate assimilation. This work contributes with an initial picture of proteins presenting differential accumulation in industrial contaminant yeast, in strict association with possible metabolic responses to nitrate as sole nitrogen source in cultivation medium.

The present study investigated the gene expression at translational level of yeast D. bruxellensis for nitrate assimilation. This study corroborated with biological models that consider the ability to assimilate this nitrogen source confers advantages on this yeast during the fermentation process industry. However, larger studies are needed in this way as our group is investigating new proteins under LC-MS/MS approach. Together, these studies will help in understanding the operation of networks and cellular regulation of the process of assimilation of nitrogen sources for the D. bruxellensis, unravelling new aspects of the physiology of this yeast by proteomic analysis. This article is part of a Special Issue entitled: Environmental and structural proteomics.