MICROBIAL ENZYMES AND THEIR APPLICATION IN CELLULOSIC ETHANOL INDUSTRY

GHIO, SILVINA; ONTAÑON, ORNELLA; PICCINNI, FLORENCIA E.; GARRIDO, MERCEDES M; CAMPOS, ELEONORA

Congreso; 54 Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2018

SAIB

Lignocellulosic biomass recalcitrance is based on the complex polymeric network of cellulose, hemicellulose and lignin that provides plantswith strength and resistance. For this reason, enzyme-mediated hydrolysis of lignocellulose, to release soluble and fermentable sugars, is a keystep for lignocellulosic based biofuels. Lignocellulosic biomass is deconstructed by the concerted action of multiple enzymes, mainly endo andexo-acting glucanases (EC γ.β.1.91; EC γ.β.1.74), xylanses (EC γ.β.1.8), ȕ-glucosidases (EC γ.β.1.β1) and ȕ-xylosidases (EC 3.2.1.37) as wellas enzymes with auxiliary or debranching activity (such as LPMOs and arabinofuranosidases). These enzymes are collectively referred to asCAZymes (carbohydrate active enzymes). The general objective of our group is the study of the enzymatic mechanisms of hydrolysis ofpolysaccharides in order to develop novel and improved enzymes for industrial applications in the degradation of residual biomass, especiallyfor the production of bioethanol. We have thoroughly characterized the CAZome (all CAZymes encoded in the genome) and secretome of twobacterial cellulolytic isolates of the genera Cellulomonassp and Paenibacillus sp. Both bacteria secrete a repertoire of enzymes necessary for thedegradation of cellulose and hemicellulose, when grown on lignocellulosic biomass, although there are differences in their strategies forpolysaccharides utilization. We have also purified xylanases from both bacterial groups as well as from the fungus Pycnoporussanguienus.GH10 and GH11 xylanases present distinct structures and have different mode of action. When assayed on lignocellulosic biomass, addition ofa ȕ-xylosidase greatly imporved the conversion to xylose. Moreover, when xylanases were added to a cellulolytic commercial cocktail,cellulose conversion to glucose was improved, indicating synergy between the enzymes involved. By improving our knowledge on enzymaticdeconstruction of biomass we are able to optimize the enzymatic cocktails for different applications