Hydrolysis of extruded wheat straw with commercial enzymes supplemented with novel hemicellulose-degrading enzymes

Among pretreatments, extrusion is a very interesting candidate for biorefining. This process can provide a unique continuous reactor environment for a combination of thermo-chemical and chemical pre-treatment of lignocellulosic biomass at higher throughput and solid levels (1), leading to an increased enzymatic saccharification while allowing almost complete recovery of carbohydrates contained in lignocellulosic biomass. Consequently, cellulolytic cocktails have to be completed by a repertoire of hemicellulases for optimal sugars production from biomass. In this work, wheat straw was submitted to one-step alkaline extrusion pretreatment process (70 ºC temperature, 150 rpm speed screw and 5% g NaOH/g wheat straw) using a twin-screw extruder.

Recently, a functional metagenomic screening of a termite gut microbiome has shown powerful results in the discovery of biomass-active enzymes (2).As a result, a collection of potentially interesting biocatalysts such as xylanases, β-d-xylosidases, α-l-arabinofuranosidases or esterases were studied.

In this work, we present the development of an extrusion pretreatment process for wheat straw. This pretreatment generated a cellulose and hemicellulose rich substrate which was subsequently subjected to enzyme hydrolysis combining a commercial cellulolytic cocktail with selected hemicellulases, mainly from the metagenomic collection.

The aim of this study was to increase sugar yields from pretreated biomass and allowed the identification of interesting lignocellulose-active enzymes which significantly increased sugar production yields from extruded wheat straw.