THE CHEMICAL-STRUCTURE OF EXTRACELLULAR LIGNIN RELEASED BY CULTURES OF PICEA-ABIES

Fractionation, size exclusion chromatography thioacidolysis and C-13 NMR of released suspension culture lignin (RSCL)produced by Picea abies showed that it is intermediate in structure between milled wood lignin (MWL) isolated from cell walls and synthetic lignins produced by dehydrogenation of coniferyl alcohol (DHP). The proportion of p-hydroxyphenyl units was larger than in MWL and over 90% of these are phenolic. Phenolic groups are abundant (ca 50%) in RSCL. The low yields of thioacidolysis products indicate that the RSCL is a highly branched polymer with a large proportion of interunit carbon-carbon bonds. This indicates that when lignins are formed outside the carbohydrate matrix, the structure is changed to a large extent.