Dynamic strategies of hemicellulases production presented in Toulouse by URCA (Reims University)
During 19 and 22 May 2019, Corinne Ivaldi from project partner URCA (France) presented results about dynamic strategies of hemicellulases production for an efficient lignocellulosic biomass fractionation at CBM13 (Carbohydrate Bioengineering Meeting) in Toulouse, France.
Corinne Ivaldi in front of the poster presented at CBM13
Lignocellulosic substrates are recalcitrant to enzymatic hydrolysis. Numerous factors such as the presence of hemicelluloses and lignins are known to be responsible of the biomass recalcitrance to fractionation. These later ones are known to impede the access of cellulases to the cellulose part (development of 2G ethanol) by forming physical barriers. A physicochemical pretreatment is thus necessary to improve enzymes efficiency. One challenge for biorefineries is to develop enzymatic processes for hydrolysis of hemicelluloses to improve 1) the access of cellulases to cellulose and 2) the obtention of the constitutive molecules (pentoses, phenolic compounds) from these polymers. A thermophilic and hemicellulolytic bacterium (Thermobacillus xylanilyticus) was able to produce thermostable and hemicellulasic cocktails performant for the deconstruction of different lignocellulosic biomasses. Analyses of the genome (4Mbp representing 3900 genes predicted) allowed identifying high lignocellulolytic potential with 162 CAZYmes encoding genes that could play a role in the lignocellulose biotransformation.
The aim of this study is to understand enzymatic strategies employed by the bacterium for efficient hemicelluloses fractionation. Do the lignocellulosic substrates induce a specific or similar enzymatic strategies production according to their compositions?
For this, we studied the behavior of the bacterium while growing on several substrates with contrasted chemicals and architectures (wheat bran, wheat straw, sweet corncob, barley straw pretreated or not) as well as purified hemicellulose (xylan). Multiple approaches combining growth on the various substrates, hemicellulasic activities productions and proteomic analyses of the intracellular and extracellular proteins, were performed to identify and quantify the expression level of hemicellulases produced by the bacterium. The effect of the enzymes produced during growth on the substrates were also assessed.