Environmental degradation of cellulose under anaerobic conditions

Abstract

Cellulose is a primary structural component of plants and is one of the most abundant polymers on the Earth. Degradation of this recalcitrant component of plant biomass is an important process in the global carbon cycle and can potentially provide feedstock for biofuels. Fungi and bacteria are the primary organisms able to breakdown biomass-derived cellulose. Anaerobic bacteria, present in cellulose degrading ecosystems, such as compost piles, soils rich in organic matter, aquatic sediments, and digestive systems of herbivores, have developed efficient pathways to maximize metabolic energy from biomass degradation. In the absence of terminal electron acceptors, such as oxygen, hydrogen-producing pathways are common methods of electron carrier recycling. Electron bifurcating systems linked to hydrogen metabolism play an important role in anaerobic metabolism. In this study, samples from environmental cellulose-degrading microbial communities were collected, and the metabolic products produced during anaerobic cellulose degradation were examined. Samples from different environments produced different fermentation products from cellulose, suggesting flexibility in the fermentative degradation pathways. The most abundant products observed included hydrogen, acetate, propionate, butyrate, ethanol, and methane.