Enzymatic Synthesis of Lignin‐Based Concrete Dispersing Agents

• Published in: Chembiochem : a European journal of chemical biology 2018-07, Vol.19 (13), p.1365-1369
• Main Authors: Jankowska, Dagmara, Heck, Tobias, Schubert, Mark, Yerlikaya, Alpaslan, Weymuth, Christophe, Rentsch, Daniel, Schober, Irene, Richter, Michael
• Format: Article
• Language: English
• Subjects: 4-Aminobenzoic Acid - chemistry; Additives; Bacillus pumilus - enzymology; Bacterial Proteins - chemistry; Biocatalysis; Biopolymers; Biotechnology; Calcium Carbonate - chemistry; Concrete additives; Construction Materials; dispersing agents; Dispersion; Enzymatic synthesis; Fungal Proteins - chemistry; green chemistry; Green Chemistry Technology - methods; Laccase - chemistry; Lignin; Lignin - analogs & derivatives; Lignin - chemical synthesis; lignins; Lignosulfonates; Mortars (material); oxidoreductases; pH effects; Polymers; Pulp; Pulp & paper industry; Reagents; Silicon Dioxide - chemistry; Solubility; Sordariales - enzymology; Streptomyces coelicolor - enzymology; Sulfanilic acid; Sulfanilic Acids - chemistry; Sulfonation; Synthesis; Trametes - enzymology; Water - chemistry
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.201800064

Lignin is the most abundant aromatic biopolymer, functioning as an integral component of woody materials. In its unmodified form it shows limited water solubility and is relatively unreactive, so biotechnological lignin valorisation for high‐performance applications is greatly underexploited. Lignin can be obtained from the pulp and paper industry as a by‐product. To expand its application, a new synthesis route to new dispersing agents for use as concrete additives was developed. The route is based on lignin functionalisation by enzymatic transformation. Screening of lignin‐modifying systems resulted in functionalised lignin polymers with improved solubility in aqueous systems. Through grafting of sulfanilic acid or p‐aminobenzoic acid by fungal laccases, lignin became soluble in water at pH≤4 or pH≤7, respectively. Products were analysed and evaluated in miniaturised application tests in cement paste and mortar. Their dispersing properties match the performance criteria of commercially available lignosulfonates. The study provides examples of new perspectives for the use of lignin. Green lignin chemistry: Environmentally friendly laccase‐catalysed grafting of Kraft lignin yields modified lignins that match the properties of commercially available concrete dispersing agents. As grafting substrates, anionic amino‐substituted aromatic acids were found to be ideal for lignin biotransformation. This might provide access to new lignin modification platforms for the synthesis of innovative materials.