Enhancing the resistance of anaerobic fungus Piromyces sp. F1 to nitrovin by co-culture with Methanobrevibacter thaueri F1

Abstract:

[Background] Anaerobic fungi can be inhibited by nitrovin. The presence of associated methanogens enhances the growth of anaerobic fungi and the decomposition of lignocellulose by anaerobic fungi. However, few studies have investigated the effect of the co-cultured methanogens on stress resistance of anaerobic fungi. [Objective] The objective of this study was to investigate the effect of associated methanogen on the resistance of anaerobic fungus to nitrovin. [Methods] Mono-culture of anaerobic fungus Piromyces sp. and co-culture of Piromyces sp. and Methanobrevibacter thaueri were inoculated into fresh media with rice straw as substrate, respectively. Nitrovin hydrochloride was added to the final concentrations of 0, 5, 10 and 25 mg/L-nitrovin. Bottles were incubated at 39 °C for 96 h without shaking. Gas production and methane production were measured at intervals. At the end of fermentation, the pH was determined immediately upon removing crimp-seals and stoppers. Samples were collected for the analysis of in vitro digestibility of dry matter, digestibility of neutral detergent fiber, digestibility of acid detergent solution and digestibility of acid detergent fiber. The water-soluble end-products including formate, lactate and acetate were measured as well. [Results] In the mono-culture, nitrovin (5, 10 and 25 mg/L) significantly reduced the fermentation activity of anaerobic fungus (P<0.05). In the co-culture, no significant difference was observed when adding 5 mg/L nitrovin (P>0.05). However, the fermentation activity was significantly depressed at the concentrations of 10 and 25 mg/L. At the concentrations of 5 and 10 mg/L nitrovin, the fermentation activity of the co-culture was significantly higher than the mono-culture (P<0.05). [Conclusion] A dose effect of nitrovin on the fermentation of anaerobic fungal mono-culture and co-culture was observed. The presence of associated methanogen enhanced the resistance of anaerobic fungus to nitrovin when the concentration of nitrovin was less than 25 mg/L.