Mitigating trade barriers by standardized determination of lignin molar mass

RISE Bioeconomy, FPInnovations and VTT Technical Research Centre of Finland Ltd are working on a draft for an official ISO method for the determination of lignin molar mass. The draft will include two methods that can be used by different laboratories as reference methods, which are based on organic and aqueous size exclusion chromatography (SEC). Four samples of kraft lignin of different origin were analysed by three laboratories using the current in-house methods as well as a harmonised analytical setup. It was clear that the results differed largely between the different methods, for example, the weight average molar mass (Mw) for the LignoForce softwood lignin (LF-SW) ranged from 3,300 t0 11,100g/mol using the different methods. Harmonisation of aqueous SEC was successful. The method comprises SEC using 0l.1M sodium hydroxide as the mobile phase, a mobile phase flow rate of 0.5mL/min, Waters columns MCX 1,000A and 100,000A in series and calibration/calculation using polystyrene sulphonate standards using a linear fit. However, organic SEC was more complex and would require further investigations. Although the aqueous SEC analysis was repeatable, it was concluded that a strategy for data evaluation should be developed in order to achieve a method applicable for quality assessments

Polymerization of coniferyl alcohol by Mn3+-mediated (enzymatic) oxidation : Effects of H2O2 concentration, aqueous organic solvents, and pH

The objective of this study was to evaluate the ability of one versatile peroxidase and the biocatalytically generated complex Mn(III)-malonate to polymerize coniferyl alcohol (CA) to obtain dehydrogenation polymers (DHPs) and to characterize how closely the structures of the formed DHPs resemble native lignin. Hydrogen peroxide was used as oxidant and Mn2+ as mediator. Based on the yields of the polymerized product, it was concluded that the enzymatic reaction should be performed in aqueous solution without organic solvents at 4.5pH6.0 and with 0.75H(2)O(2):CA ratio1. The results obtained from the Mn3+-malonate-mediated polymerization showed that the yield was almost 100%. Reaction conditions had, however, effect on the structures of the formed DHPs, as detected by size exclusion chromatography and pyrolysis-GC/MS. It can be concluded that from the structural point of view, the optimal pH for DHP formation using the presently studied system was 3 or 4.5. Low H2O2/CA ratio was beneficial to avoid oxidative side reactions. However, the high frequency of - linkages in all cases points to dimer formation between monomeric CA rather than endwise polymerization. (c) 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:81-90, 2018Peer reviewe