A new lignocellulosic biomass deconstruction process combining thermo-mechano chemical action and bio-catalytic enzymatic hydrolysis in a twin-screw extruder

Abstract

A new process for the deconstruction of lignocellulosic biomass was evaluated. It combines thermo-mechano-chemical action and the bio-catalytic action of enzymatic hydrolysis in a twin-screw extruder. The process proceeds in three phases all conducted in a twin-screw extruder: an alkaline pretreatment, a neutralization phase and an enzyme impregnation phase during which hemicelluloses and cellulose saccharification begins. Four model feedstocks with high cellulose content have been selected for the study: sweet corn residue (SC), a co-product of industrial corn grain canning; blue agave bagasse (BAB) from the manufacture of tequila; oil palm empty fruit bunch (OPEFB), a residue from palm oil manufacture, and barley straw (BS). They are all agricultural or agro-industrial processing by-products, although their morphological origin, chemical composition and physical structure differ. Their differences in behavior are studied throughout the process, and their cell wall constituents, hemicelluloses, cellulose and lignin, quantified. The enzymatic hydrolysis of the four feedstocks ranged from 8 to 26% of dry matter and reached 26 to 68% of dry matter after alkaline pretreatment depending on the particular biomass. The process allows preparation of high dry matter content (>20%) cellulosic material for saccharification. The continuous treatment allows extraction of a large part of the hemicelluloses (up to 64% for SC), configures cellulose for better accessibility, and initiates cellulose depolymerization by the enzyme cocktail during bioextrusion. This new process is advantageous because it minimizes energy consumption by operating at a low temperature, minimizes water consumption by working at a low liquid/solid ratio and is fast and adaptable to different biomasses.