4.6 Biocatalytic membranes from lignin-based fibres and nanoparticle building blocks

Lignin is the most abundant natural polyphenolic polymer in the world. Among different categories of lignin, Kraft lignin is obtained as a by-product from the paper and pulp industry. There are many reasons why lignin could be used in engineered materials, including its properties such as cation-exchange capacity, adsorption capacity, amphiphilic nature, biodegradability as well as presence of many active functional groups. However, complex aromatic structure, limited solubility as well as broad molecular weight distribution are common obstacles for using lignin as an efficient bio-material. Recently, renewable materials are getting increased attention in many fields such as waste water treatment. Attempting to overcome the limitations of lignin, our idea is to fabricate bio-catalytic membranes solely from lignin-based building blocks such as lignin nano-particles, lignin nano-fibers as well as lignin microfibers. These lignin-based membranes will offer an alternative to the present bio-catalytic membranes that are fabricated from synthetic polymers. Synthesis of lignin nano-particles for enzyme immobilization has already been reported from the group by solvent-shifting method. Also, our group has developed a new method for formation of lignin microfibers by melt-spinning. In addition, we have established electrospinning for producing lignin-based nano-fibers. Our current efforts aim to assemble all of these components together to fabricate lignin-based composite membranes and equip them with enzymes allow using them in separation processes.