Microecological insight into the microbial structure, key cellulolytic community, and microbial interaction during cellulose degradation in high-diversity and low-diversity communities

Inadequate management of lignocellulosic waste poses a risk of substantial environmental pollution. Enriched microbial communities selected from environmental samples can effectively contribute to lignocellulose degradation. Utilizing a lower diversity but equally effective microbial community can enhance the control and efficiency of industrial operations. However, the mechanisms of cellulose degradation and functional microbial interactions within microbial communities with reduced diversity remain unclear. In this study, high-diversity and low-diversity lignocellulose-degrading communities were constructed using the dilution-to-stimulation and dilution-to-extinction methods. The enzymatic activity, community composition, degradation pathways, key functional microbes, and microbial co-occurrence network during cellulose degradation were analyzed in both high-diversity and low-diversity communities at the DNA and RNA level. Results showed that the low-diversity community exhibited a higher substrate degradation rate than the higher-diversity community. The activity of FPase and CMCase in the low-diversity community was significantly higher. <i>Sphingobacterium</i>, <i>Pseudoxanthomonas</i>, and <i>Devosia</i> were key players in the high-diversity community. <i>Cellulomonas</i> played a significant role in the low-diversity community. Reducing community diversity strengthens the cooperation among functional microbes. This study can guide the design of functional microbial synthetic communities and also can help to expand the ecological understanding of lignocellulosic waste degradation in synthetic microbial systems.IMPORTANCEMicrobial community diversity is pivotal in the degradation of lignocellulose. Nonetheless, reducing microbial diversity does not invariably result in decreased degradation efficiency. The utilization of low-diversity communities offers several advantages in industrial applications. Previous studies on lignocellulose-degrading functional microbial communities with low diversity have predominantly concentrated on community composition, with limited investigation into functionality and microbial interaction mechanisms. In this study, we constructed microbial communities with high and low diversity to investigate their efficiency in lignocellulose degradation and to elucidate the microbial ecological mechanisms. Our findings indicate that communities with low diversity decreased microbial competition and altered the composition of key functional microbes during the lignocellulose degradation process, thereby enhancing the efficiency of lignocellulose degradation. Investigating the microbial ecological mechanisms underlying lignocellulose degradation in both high- and low-diversity microbial communities can aid in the design of synthetic functional microbial communities and significantly contribute to the bioconversion of lignocellulosic waste.