Fungal dynamics and potential functions during anaerobic digestion of food waste

Fungi could play an important role during anaerobic digestion (AD), but have received less attention than prokaryotes. Here, AD bioreactors of food waste were performed to explore fungal succession and their potential ecological and engineering value. We found that similar patterns in fungal biomass and diversity, decreasing from the initial time point (Day 0) to the lowest value within 3-6 days and then started to rise and stabilized between 9 and 42 days. Throughout the entire AD process, variations in fungal community composition were observed and dominant fungal taxa have the potential ability to degrade complex organic matter and alleviate fatty acid and ammonia accumulation. Furthermore, we found that deterministic processes gradually dominated fungal assembly succession (up to 84.85% at the final stage), suggesting changing environmental status responsible for fungal community dynamics and specifically, fungal community structure, diversity and biomass were regulated by different environmental variables or the same variables with opposite effects. AD bioreactors could directionally select specific fungal taxa over time, but some highly abundant fungi could not be mapped to any fungal species with defined function in the reference database, so function prediction relying on PICRUSt2 may underestimate fungal function in AD systems. Collectively, our study confirmed fungi have important ecological and engineering values in AD systems.

Automated summary

This study investigated fungal succession and their ecological and engineering value in anaerobic digestion (AD) systems using food waste. The results showed that fungal biomass and diversity followed a similar pattern, decreasing from the initial time point and then rising and stabilizing. The dominant fungal taxa had the potential to degrade complex organic matter and alleviate fatty acid and ammonia accumulation. The fungal community structure and composition changed during the AD process, and the assembly succession was mainly determined by environmental changes. AD bioreactors could select specific fungal taxa over time, but function prediction based on existing databases may underestimate fungal function. Overall, fungi have important ecological and engineering values in AD systems.