A TWO-STEP, BACTERIAL-YEAST COMPLEMENTATION FOR LIGNOCELLULOSE CONVERSION TO BIO-ETHANOL

摘要

Lignocellulosic biomasses, such as crops, wood, grass and food waste, are sustainable potentialrnresources for bio-ethanol production. Out of the three main steps needed for the conversion process (pretreatment,rnenzymatic degradation and fermentation), the pretreatment, which can be chemical or microbial, is the most crucialrnone. In this work we provide evidence that wood flour, a common waste sub-product of wood furniturernmanufacturing, is the ideal substrate for an efficient microbial pretreatment of lignocellulose. We isolated from thernbovine rumen two strains of B. pumilus and B. licheniformis that were deeply characterized and tested for theirrnability in lignocellulose pretreatment. Moreover, the enzymatic degradation step can be partially completed by thernsame microorganisms producing a mixture of glucose and cellobiose. We further developed genetically engineered,rnrecombinant yeast strain capable of vigorous growth using cellobiose as the only carbon source. We thereforerndemonstrated that the sequential treatment of wood flour firstly by Bacilli and secondly by S. cerevisiae allows anrnefficient and economic conversion of biomass into glucose leading to interesting perspectives in bio-ethanolrnproduction.