An efficient enzymatic-based process for the extraction of high-mechanical properties alfa fibres

• An optimised process for alfa fibres extraction is proposed.
• It combines mechanical, chemical and enzymatic steps.
• Tensile properties of isolated fibres are improved with optimised enzymatic activities.
• Alfa fibres are promising reinforcements for load-bearing composite materials.
• Enzymes offer an attractive eco-friendly approach to efficiently extract plant fibres.

Alfa fibres, which are generally extracted from the leaf of a plant belonging to the Poaceae family (Stipa tenacissima L), originating from the center of Tunisia, are mainly used for pulp and paper applications. Their potential use as reinforcement in polymer composites requires the understanding of their microstructure and mechanical properties and a proper control of fibre extraction and transformation processes. This work investigates the morphology of the alfa plant (leaves and fibres) through optical and electron microscopy. The extraction process combining mechanical, chemical and enzymatic stages and the reaction time of the enzymes have been optimised to achieve the highest mechanical properties of fibres. The effect of enzymatic treatments (laccase, pectinases and xylanases) on the morphological, chemical composition and mechanical properties of alfa fibres was investigated and the effectiveness of enzymatic treatments has been evaluated. The chemical compositions of alfa are correlated with its mechanical properties. The result indicates that the tensile properties of isolated fibres were greatly improved when an optimised enzymatic-based process is used to separate the fibres from the leaves. Using pectinase and xylanase activities, results show really high mechanical properties, with an average rigidity and strength up to, respectively, 66 GPa and 1300 MPa, which make alfa fibre promising reinforcements for load-bearing composite materials. This work also showed that enzymes offer an attractive and eco-friendly approach to efficiently extract high-performance plant fibres.