Fractionation and characterization of ball-milled and enzyme lignins from abaca fibre

✍ Scribed by Sun, RunCang; Fang, J?M; Goodwin, A; Lawther, J?M; Bolton, A?J

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 137 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199906)79:8<1091::aid-jsfa331>3.0.co;2-a

✦ Synopsis

Ball-milled and enzyme lignins were produced from abaca ®bre via ball milling for 6 days followed by cellulase treatment for 3 days. The crude lignin preparations were fractionated into milled lignin (ML), enzyme lignin (EL), hemicellulose-rich milled lignin (HRML), and lignin-rich enzyme lignin (LREL) fractions using a two-step precipitation method instead of a traditional ether precipitation procedure. The yield and chemical composition of the resulting lignin samples are reported. The ML and EL fractions contained low amounts of associated neutral sugars (2.0±3.3%) and uronic acids (1.4±1.5%), and showed relatively low average molecular weights (2500±2660), while the LREL and HRML fractions contained large amounts of bound polysaccharides (35.6±38.3%), and showed high molecular weights (8800±25000). The four lignin fractions are composed of a large proportion of syringyl units with fewer guaiacyl and p-hydroxyphenyl units. The ML is mainly composed of b±O±4 ether bonds between the lignin structural units. The less common b±b, b±5 and 5±5' carbon±carbon linkages are also present in the lignin molecules. It was found that uronic acids and 41± 63% of p-coumaric acids are esteri®ed to lignin in the three lignin-rich fractions of ML, EL and LREL. This level increased to over 90% in the hemicellulose-rich fraction of HRML. For ferulic acids, 92±97% were found to be etheri®ed to lignin in the three lignin-rich fractions of ML, EL and LREL, while in the hemicellulose-rich fraction of HRML this reduced to only 13%, suggesting that a majority of the ferulic acids are esteri®ed to hemicelluloses or lignin in this fraction.