Anaerobic co-fermentation of straw and manure is widely used for waste treatment and biogas production. However, there is a lack of knowledge on the differences between the straw- and slurry-associated prokaryotic communities, their dynamic changes throughout the co-fermentation process, and their correlations with bioreactor performance. To address these questions, researchers from Chengdu Institute of Biology of CAS investigated the prokaryotic community compositions and the dynamics of prokaryotes during co-fermentation of wheat straw and swine manure using pyrosequencing technique.

Due to the difference in physicochemical nature of straw and slurry, prokaryotic community structure and function throughout the process differentiated. Straw-associated prokaryotic communities were over-represented by the phyla Spirochaetes and Fibrobacteres, while Synergistetes and Euryarchaeota were more abundant in the slurry. The straw-associated candidate class TG3, genera Fibrobacter, Bacteroides, Acetivibrio, Clostridium III, Papillibacter, Treponema, Sedimentibacter and Lutispora may specialize in substrate hydrolysis.

However, sropionate was the most abundant volatile fatty acid in the slurry, and it was probably degraded through syntrophic oxidation by the genera Pelotomaculum, Methanoculleus and Methanosaeta. The protein fermenting bacteria Aminobacterium and Cloacibacillus were much abundant in the slurry, indicating that proteins are important substrates in the co-fermentation.

This study provided a better understanding of the anaerobic co-fermentation process that is driven by the specific and different spatially distributed microbiota in the system, which could be useful information to improve the process performance as well as troubleshooting issues with regard to reactor performance.This research has been published in Applied Microbiology and Biotechnology.