Comparative metagenomic discovery of the dynamic cellulose-degrading process from a synergistic cellulolytic microbiota

Abstract

Background As a green and sustainable bioenergy source, cellulose is difficult to degrade due to its large molecular weight and high structural complexity. Many cellulolytic microorganisms can secrete a series of enzymes to synergistically catalyze the cellulose degradation with a high efficiency. However, the inability to cultivate most of them, as well as their spatial diversity and temporal variability, limit the clear understanding of the relative area. Results To reveal the dynamic process of cellulose biodegradation, we cultivated a microbiota (FP) with efficient cellulose-degrading ability and compared the different stages of filter paper degradation. Ion chromatography and comparative metagenomic sequencing revealed that the diversity of FP enhanced as the complexity of hydrolysates increased, and the disturbance of FP was greater in early-intermediate than intermediate-final period. Sporocytophaga myxococcoides and Cohnella sp. CIP 111063 dominated the synergistic degradation of cellulose in early-intermediate and intermediate-late stages, respectively. Totally, 432 genes were annotated to cellulolytic pathways, and 363 and 231 unannotated genes were speculated to be related to the degradation of cellulose to cellodextrin/cello-oligosaccharide and cellobiose, respectively. Finally, according to the temporal changes in hydrolysates, community structure and gene abundances, a dynamic cellulose-degrading pathway was designed, which involved key cellulolytic species and enzymes in FP. Conclusions The cellulose-degrading pathway was established based on the dynamic analysis in microbiota FP, suggesting the collaboration and competition between species during cellulose degradation. Our work should provide a new perspective for the subsequent identification of key cellulolytic strains and enzymes and clarification the mechanism of cellulose biodegradation.