Analysis of retted and non retted flax fibres by chemical and enzymatic means

Flax fibres (Linum usitatissimurn L.) were subjected to chemical and enzyma tic analysis in order to determine the compositional changes brought about by the retting process and also to determine the accessibility of the fibre polymers to enzymatic treatment. Chemical analysis involved subjecting bot h retted and non retted fibres to a series of sequential chemical extractio ns with 1% ammonium oxalate, 0.05 M KOH, 1 M KOH and 4 M KOH. Retting was s hown to cause minimal weight loss from the fibres but caused significant ch anges to the pectic polymers present. Retted fibres were shown to have sign ificantly lower amounts of rhamnogalacturonan as well as arabinan and xylan . In addition the average molecular mass of the pectic extracts was conside rably lowered. Enzyme treatment of the 1 M KOH extracts with two different enzymes demonstrated that the non retted extract contained a relatively hig h molecular weight xylan not found in the retted extract. Treatment of the 1 M KOH extracts and the fibres with Endoglucanase. V from Trichoderma viri de demonstrated that while this enzyme solubilised cellulose as well as xyl an and xyloglucan oligomers from the extract, it had limited access to thes e polymers on the fibre. MALDI-TOF MS analysis of the material solubilised from the extract suggested that the xylan was randomly substituted with 4-O -methyl glucuronic acid moieties. The xyloglucan was shown to be of the XXX G type and was substituted with galactose and fucose units. The enzyme trea tments of the fibres demonstrated that the xylan and xyloglucan polymers in the fibres were not accessible to the enzyme but that material which was e ntrapped by the cellulose could be released by the hydrolysis of this cellu lose. (C) 2001 Elsevier Science B.V. All rights reserved.