Improving syntrophic metabolism of propanol for biomethane production with carbon cloth replacing microbial nanowires

Abstract

In order to promote direct electron transfer between Geobacter metallireducens and Geobacter sulfurreducens, electroconductive interspecies nanowires were replaced by carbon cloth with low electrical resistivity and high surface area to improve propanol metabolism for CH4 production. Scanning electron microscopy images showed that numerous nanowires existed in syntrophic cocultures, whereas none were observed with carbon cloth. Conducting-probe atomic force microscopy detected that interspecies nanowires had an average electrical resistivity of 0.35Ω·cm, which was much higher than that (0.0016Ω·cm) of carbon cloth. The 76.2% microorganisms concentrated in biofilms of carbon cloth with surface area of 8.4m2/g, which promoted direct interspecies electron transfer. Fourier transform infrared spectra indicated that most polysaccharides metabolite from microorganisms in biofilms dissolved in supernatant. The propanol degradation rate improved by 25% with 4.0g/L carbon cloth to promote CH4 yield by 48.6% (to 194.1mL/g propanol) and production rate by 42.9% (to 37.3mL/g propanol/d).