Study of transcription factor expression of Aspergillus niger possibly related to the plant biomass degradation

Abstract

The dependence on fossil fuel sources as well as the concern about the environment has generated a worldwide interest in establishing new sources of fuel and energy. In this sense, the use of ethanol as fuel is advantageous given its inexhaustible energy source and minimal environmental impact. Brazil is currently the world's second largest producer of ethanol manufactured from the fermentation of sugar cane juice. However, several studies suggest that the further use of bagasse and straw could double the Brazilian production per hectare. Nevertheless, the use of this additional biomass presents a challenge, because it is necessary to degrade the plant cell wall structure (composed of complex sugars such as cellulose and hemicellulose) into single fermentable sugar such as glucose. To achieve this goal, several types of hydrolytic enzymes are required. These enzymes are produced by a variety of microorganisms, like Aspergillus niger, capable of producing and secreting them in large quantities. Although several studies have been performed with this fungus, our understanding of the exact mechanisms of degradation of these substrates remains unclear. In this sense, it is important to know which are the transcription factors related to the biomass degradation. Transcription factors are the major regulators of expression of gene networks, having an essential role in most biological processes. This scientific initiation proposal will be developed in an ongoing research project (2011/08945-9), with the main goal to analyze the global gene expression of A. niger cultivated on medium containing only bagasse or culm from sugarcane as substrate, using massively parallel high-throughput sequencing of cDNA (RNA-seq). In this work some putative transcriptions factors have been identified, which are up regulated when the fungus grows on media containing only recalcitrant substrate as single carbon source (in relation to the control condition, fungus growing on fructose). This proposal aims to validate the expression of some of those transcription factors using real time PCR, growing A. niger in different carbon sources. Beyond the contribution on the understanding of basic rules involved in the sugar cane degradation, the resulting knowledge has the potential to generate new perspectives for the development of enzyme cocktails, enabling the large-scale production of second-generation ethanol. (AU)