Biosynthesis of highly flexible lignosulfonate–starch based materials

Abstract

The need to replace polymers from fossil sources with bio-based renewable sources is increasingly imminent. This work reports on the synthesis of biofilms obtained from the polymerization of lignosulfonates using laccase as a biocatalyst and blending with starch. The effect of the reaction conditions on the formation of stable starch-lignosulfonate polymers was evaluated by monitoring changes in viscosity, molecular weight (Mw), and fluorescence measurements. Enzymatic polymerization led to molecular weights of ∼ 400 kDa and viscosities of ∼ 1.00 Pas and decreases in lignosulfonates-OH groups by about 46% after 1 h of reaction carried out at pH 7 and adding starch at the end of the polymerization reaction. Additionally, the effect of the starch concentration on the mechanical, thermal, and water absorption properties was studied. As a result, the addition of up to 7% starch was found to improve the mechanical properties of the lignosulfonate films as indicated by the increase in elongation at break, tensile strength, and Young's modulus, reaching values of 157%, 1.19 MPa, and 0.22 MPa, respectively. This study demonstrated a green alternative for creating 100% biobased films composed of starch and lignosulfonates.