Enzymatic polymerisation and effect of fractionation of dissolved lignin from Eucalyptus globulus Kraft liquor

• Published in: Bioresource technology Vol. 121; pp. 131 - 138
• Main Authors: Gouveia, S., Fernández-Costas, C., Sanromán, M.A., Moldes, D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2012
• Subjects: Chemical Fractionation; Chromatography, Gel; Dissolution; Eucalyptus; Eucalyptus - chemistry; Eucalyptus globulus; experimental design; Fourier transform infrared spectroscopy; Fourier transforms; Fractionation; Hydrogen-Ion Concentration; Infrared spectroscopy; Kraft dissolved lignin (KDL); Laccase; Laccase - metabolism; Lignin; Lignin - analysis; Lignin - metabolism; Lignin fractionation; Molecular weight; Myceliophthora thermophila; Polymerisation; Polymerization; size exclusion chromatography; Sordariales - enzymology; Spectroscopy, Fourier Transform Infrared; Temperature; Lignin fractionation; Lignin; Polymerisation; Kraft dissolved lignin (KDL); Laccase
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2012.05.144

[Display omitted] ► The ability of laccase to polymerise Kraft dissolved lignin was evaluated. ► Lignin fractionation was carried out to improve the polymerisation degree. ► A comparison between solvent extraction and acidic fractionation was accomplished. ► S/G ratio of the lignin fractions may play an important role in polymerisation degree. ► An increase of the lignin Mw, with a factor ranging from 4 to 21, was achieved. The potential ability of the laccase from Myceliophthora thermophila, either alone or with low molecular weight (LMW) additives, to polymerise a dissolved lignin from Kraft liquor of eucalypt cooking was investigated. A previous study of enzymatic performance (activity and stability) was carried out using a design experiment methodology. In addition, Kraft dissolved lignin (KDL) was fractionated according to two different protocols (solvent extraction and acidic fractionation) in order to identify possible lignin fractions with noticeable polymerisation ability. KDL and its corresponding lignin fractions were treated with laccase and analysed by size exclusion chromatography and Fourier transform infrared spectroscopy. The results provide conclusive evidence of notable lignin modifications after incubation with laccase. Moreover, lignin fractionation allows to obtain lignin fractions with different chemical characteristics and polymerisation capability. Depending on the type of raw lignin, molecular weight can increase from 4- to 21-fold by means of laccase polymerisation.