SMOLBnet 2.0: Structural studies of transcription factors involved in the regulation of hydrolytic enzyme genes and swollenin from Aspergillus niger and A. fumigatus

Abstract

The high cost of reducing complex polysaccharides to fermentable sugars from biomass remains the main obstacle for the large-scale production of cellulosic ethanol. The cost of cellulases and hemicellulases contribute substantially to the price of ethanol and, therefore, further studies aimed at understanding and improving the efficiency and stability of these enzymes are of fundamental importance. The filamentous fungus Aspergillus niger is a major producer of such proteins, and their expression is regulated by transcription factors XlnR and CreA. A detailed study may allow the design of modified forms of these transcription factors leading to constitutive expression or independent of inducer / repressor, enabling higher production of enzymes for lignocellulosic biomass processing. Another important way to boost the production of bioethanol is the improvement of enzymes, which are involved in the process of cell wall degradation. Therefore, we also propose to study proteins whose level is regulated by the transcription factors, XlnR and CreA. The accumulation of knowledge, mainly in biophysical and structural aspects, will aid to rationally modify these enzymes in order to make them more stable and highly active under conditions imposed by industrial processes. Expansins are proteins from plants without hydrolytic activity that promotes the breakdown of the crystallinity of cellulose microfibrils. The swollenins, a group of expansins, have been shown to be important for efficient saccharification of the cell wall and therefore they were also included in this project. The structural studies of these proteins will be used for comparisons with the expansins, which have similar activity but different structural organization and can contribute to determine their mode of action. Thus, synergistically, we hope to provide structural data at molecular level which can help to elucidate the molecular mechanisms involving gene regulation of hydrolytic enzymes as well as from their genes that have key role in the degradatation of lignocellulosic biomass. It could enable new strategies for economically viable production of second-generation bioethanol from the material currently considered a waste by bioethanol industry. (AU)