Isolation and biomethane production characterization of a novel co-culture of anaerobic fungus and methanogen

Abstract:

[Background] Exploiting biomethane resources is an effective way to alleviate the shortage of fossil fuel supply nowadays. At the same time, the methods of lignocellulosic biomass pretreatment and methane production need to be innovated for sustainable development. The co-cultivation of anaerobic fungi and methanogens enables dual pretreatment of lignocellulosic biomass and methane production by rhizoid invasion and fiber-degrading enzymes. However, only one culture of anaerobic fungi isolated from camel gut has been reported in the world. [Objective] To isolate and identify the novel co-culture of anaerobic fungus and methanogen from the rumen contents of Xinjiang Bactrian camels, and investigate its application potential in degrading lignocellulosic biomass and producing biomethane. [Methods] The co-culture of anaerobic fungus and methanogen was isolated by Hungate rolling-tube technique from camel gastrointestinal tract and then identified based on the morphological and molecular characteristics. Further, the biomethane production, degradation efficiency, and primary metabolites of the co-culure were determined by anaerobic fermentation with five substrates (rice straw, reed, Broussonetia papyrifera leaves, alfalfa stalk, and Melilotus officinalis). [Results] The co-culture CR1 of anaerobic fungus and methanogen was composed of Oontomyces sp. CR1 and Methanobrevibacter sp. CR1, which had high xylanase activity (21.64 IU/mL) and biomethane production (143.39 mL/g-DM) when degrading rice straw. Furthermore, CR1 had better methane production property than the anaerobic fungal co-cultures isolated from other animals. [Conclusion] The co-culture CR1 of anaerobic fungus and methanogen is a novel degrading strain with high efficiency, which has a promising application prospect in the production of biomethane from lignocellulosic biomass.