Structural modification of alfalfa stems during hot water and enzymatic hydrolysis for sugar production

Bioethanol production from non-food lignocellulosic material is one of the most important topics in the field of biofuel production. We report on experiments with a treatment for the production of fermentable sugars from the fibrous parts of alfalfa (Medicago sativa L.), a widely used forage plant. The process is divided into several consecutive steps: ball milling, microwave assisted pretreatment in aqueous medium and enzymatic hydrolysis with a mixture of cellulase and β-glucosidase leading to the final production of fermentable sugars. This process was followed by a detailed HPLC analysis for the detection of sugars, oligomers and by-products, such as furfural, hydroxymethylfurfural and acids. Scanning electron microscopy was used for a visual characterization of the material throughout all these steps. Several plant structures were identified and their successive changes during the different treatment steps were monitored and followed.