Anaerobic Degradation of Soluble Fractions of [ 14 C-Lignin]Lignocellulose

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Abstract
[14C-lignin]lignocellulose was solubilized by alkaline heat treatment and separated into different molecular size fractions for use as the sole source of carbon in anaerobic enrichment cultures. This study is aimed at determining the fate of low-molecular-weight, polyaromatic lignin derivatives during anaerobic degradation. Gel permeation chromatography was used to preparatively separate the original 14C-lignin substrate into three component molecular size fractions, each of which was then fed to separate enrichment cultures. Biodegradability was assessed by monitoring total carbon dioxide and methane production, evolution of labeled gases, loss of 14C-activity from solution, and changes in gel permeation chromatographic elution patterns. Results indicated that the smaller the size of the molecular weight fraction, the more extensive the degradation to gaseous end products. In addition, up to 30% of the entire soluble lignin-derived carbon was anaerobically mineralized to carbon dioxide and methane.