Feeding strategy determine flexible biogas via shaping microbial abundance and interaction in anaerobic digestion

The optimization of anaerobic digestion systems for enhanced biogas production is reliant on the manipulation of feeding regimes and organic loading. However, the impact of these operations on the microbiota remains unclear. Here, the effects of three distinct feeding regimes (once daily, every 2nd day, and every 3rd day) with two different loading amounts (300 g and 500 g) were investigated in 2 continuously stirred tank reactors treating swine manure. Results indicated that the high organic loading (500 g daily feeding) resulted in increased biogas and methane production, albeit with reduced archaeal alpha diversity. Furthermore, a significant alteration in species distribution was observed with sudden feeding regime changes (300 g every 2nd day) and higher organic loading. Wherein, the core species determined the methane production regarding the different organic loading. The resultant species turnover likely drove the increased biogas production while species loss contributed to the fluctuation of biogas production in intermittent feeding regimes. Despite a decrease in positive connections with high organic loading, the connectivity of Methanosarcinaceae with bacteria increased, thus ensuring higher biogas production. In conclusion, the present study underscores the association between feeding strategies and elevated levels of organic loading with regards to the interdependence between methanogenic microorganisms and keystone bacterial populations. As a consequence, this interplay exerts a discernible influence on the biogas production process.