Bioaugmentation with methanogens cultured in a micro-aerobic microbial community for overloaded anaerobic digestion recovery. (August 2022) - Hua, Binbin
Abstract: Anaerobic digestion (AD) is widely used for conversion of waste materials into biogas, but inhibition of methane production caused by overloading can be a major problem. The micro-aerobic microbial community MC1 was used to successfully culture methanogens, Methanosarcina acetivorans C2A and Methanosaeta thermophila NBRC 101360. The maximum 16S rRNA gene concentrations of Methanosarcina acetivorans C2A and Methanosaeta thermophila NBRC101360 were 1.06 × 10 6 and 1.35 × 10 3 copies/mL, respectively. The five key bacteria in MC1 were quantified to assess the effect of inoculation on the abundances of the bacteria in the mixed culture. The original MC1 total 16S rRNA gene concentration was 1.93 × 10 8 copies/mL, and the total 16S rRNA gene concentration had increased to 4.79 × 10 9 copies/mL on day 9 (p < 0.05). The proportions of the key strains in MC1+MST had changed by day 9. Cells were harvested and used to bioaugment and increase the pH values of the high- and medium-temperature anaerobic systems. After bioaugmentation, thermophilic AD recovered well. The cumulative amounts of gas produced were 44.78% and 28.28% higher in the MC1+MST and MC1 groups, respectively, than the sterilized control. The MC1+MST group gave better results than the chemical addition control group (CaCO3 ). There was no clear effect of bioaugmentation in mesophilic AD. When compared with traditional pure culture of methanogens as inoculants, methanogen cultivation in MC1 was simple and there was no need to separate and purify the target strains. This simplified methanogenic bioaugmentation agent was useful to study the mechanism of bioaugmentation for the recovery from low pH inhibition, showing the potential for practical application. Graphical abstract: Image 1 Highlights: MC1 provided the necessary conditions for growth of acetoclastic methanogens. Compared with MC1, the proportions of the key strains changed in MC1+MST. MC1-grown methanogens accelerated the recovery of the AD process. By augmented MC1+MST, biogas production increased by 44.78%. MC1 provided a simple procedure for cultivating bioaugmentation seeds.