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Anaerobic digestion technology is widely used to treat various organic wastes such as straw, manure, garbage, sewage, etc.
, and to produce renewable energy biogas, which is recognized as one of
the most effective carbon neutral technologies.
In the anaerobic digestion process, propionic acid is an important intermediate metabolite, because the Gibbs free energy in the process of propionic acid degradation is positive, in high-load anaerobic digestion, propionic acid is the easiest to accumulate, eventually leading to reactor instability or even collapse
.
Propionic acid oxidizing bacteria are the main microorganisms that oxidize propionic acid to acetic acid and H2/CO2, which are subsequently converted to CH4 by methanogenic bacteria
。 Therefore, enhancing the interaction between propionic acid oxidizing bacteria and methanogenic bacteria and enhancing the degradation of propionic acid to produce methane is essential
for the stability of anaerobic digestion.
In order to better understand this mutual operation mechanism and enrich the high-concentration propionic acid reciprocating methanogenic bacteria strain to improve the anaerobic digestion efficiency and reactor load, the biomass energy project team of the Chengdu Institute of Biology, Chinese Academy of Sciences used biogas engineering fermentation broth as the inoculum, selected propionic acid as the only substrate of the anaerobic digestion system, and used daily one-time acid addition to increase the propionic acid load from 0.
2 g/(L· d) Gradually increase to 2.
7 g/(L· d)
。 At 2.
7 g/(L· d) When loaded, propionic acid accumulates seriously in the system and the stability of the system is reduced
.
By stopping acid feeding, system stability is gradually restored
.
After that, the acid feeding method was changed, and the medical syringe pump was used to slowly feed the acid, and the system load was raised to 2.
4 g/(L·d) again, and the system operated stably without propionic acid accumulation
.
Microbial community diversity analysis showed that the microbial communities and interactive microorganisms of the system were different in different propionic acid loading stages and different
injection methods.
And in the slow acid progression stage, the structure of the system microbial community is more stable, and the main interactive microorganisms are Syntrophobacter and Methanosaeta
。 Functional gene prediction revealed that when the propionic acid shock is strong, the hydrogen-based methanogenic pathway is the main methanogenic metabolic pathway of the system, which can quickly reduce the partial pressure of hydrogen and enhance the stability of
the system.
However, when the injection method is changed to slow acid feeding, due to the reduction of the shock load of the system, the system switches to a milder acetic acid methane production pathway
.
This research was supported by the National Key Research and Development Program of China (2019YFD1100603).
Related scientific research results "The microbial and functional reconstruction of instable syntrophic propionate-oxidizing methanogenesis by system recovering and injection modes changing" With researcher Li Dong and joint master's student Meng Xianghui as the co-first author, assistant researcher Cao Qin as the corresponding author, it was published in the Chemical Engineering Journal.
Original link
Control diagram
