Microbial community succession associated with corn straw degradation in a bacterium consortium

Abstract:

[Objective] The aim was to attain the optimal conditions for the degradation of corn straw by microbial lignin-degradation consortium and define the functional microbes that are important for the degradation of corn straw. [Methods] Based on the results of single factor experiments, such as culture temperature, pH, media loading quantity and inoculation concentration, the response surface method was adopted to optimize the culture conditions for the degradation of corn straw by the consortium. The changes of community structure in different stages of degradation were analyzed by high-throughput sequencing of bacterial 16S rRNA amplicons. [Results] The optimum degradation conditions were as follows:fermentation temperature 32℃, pH 8.2, loading volume 40%, inocula concentration 10%, under which the degradation rate of lignin was up to 44.5%. Compared with the non-optimized treatment, the increased rate of lignin degradation was 13.3%. At the phylum level, Proteobacteria, Bacteroidetes and Firmicutes were dominant. The dominant genera included Proteiniphilum (11.9%), Sphaerochaeta (8.4%), Ruminofilibacter (8.4%), Pannonibacter (6.7%), Pseudomonas (6.1%) and Rhizobium (5.7%) in initial stage. In the peak stage of lignin degradation, the abundance of Anaerocolumna (24.0%), Caenispirillum (9.2%) and Thauera (7.0%) increased significantly, it was 16.5, 3.0 and 5.9 times higher than that at the initial stage of degradation. Meanwhile, the abundance of Ruminofilibacter (10.9%) was still very high and ranks second. The mainly dominant genera at the end of degradation were Ruminofilibacter (25.4%), Pseudomonas (9.7%), Sphaerochaeta (8.8%), Caenispirillum (8.4%), Pannonibacte (4.3%), Thauera (4.0%) and Desulfomicrobium (3.4%). [Conclusion] The optimal conditions of corn straw degradation and the dynamic changes of bacterial consortium structure were clarified. Pseudomonas, Pannonibacter, Thauera, Ruminofilibacter and Anaerocolumna were main bacteria that have played an important role in the process of corn straw degradation.