Microbial Community Analysis of Digested Liquids Exhibiting Different Methane Production Potential in Methane Fermentation of Swine Feces

• Published in: Applied biochemistry and biotechnology 2020-07, Vol.191 (3), p.1140-1154
• Main Authors: Nakamura, Yoshitaka, Ishibashi, Matsujiro, Kamitani, Yoshinori, Tsurumaru, Hirohito
• Format: Article
• Language: English
• Subjects: Abundance; Acetic acid; Acetic Acid - chemistry; Acetogenesis; Ammonia - chemistry; Animals; Autoclaving; Bacteria; Biochemistry; Biological Oxygen Demand Analysis; Bioreactors; Biotechnology; Chemical oxygen demand; Chemistry; Chemistry and Materials Science; Cultivation; Decomposing organic matter; Decomposition; Fatty Acids, Volatile - analysis; Feces; Fermentation; Hydrogen-Ion Concentration; Liquids; Manure; Methane; Methane - chemistry; Methanogenesis; Methanosarcina - metabolism; Microbiomes; Microbiota; Microorganisms; Nitrogen - chemistry; Organic matter; Relative abundance; RNA, Ribosomal, 16S - genetics; Sewage; Sludge; Sludge digestion; Substrates; Swine; Waste Disposal, Fluid - methods
• ISSN: 0273-2289; 1559-0291
• DOI: 10.1007/s12010-020-03228-7

Batch methane fermentation was conducted using seed sludge collected from six methane fermentation facilities. Swine feces were centrifuged and autoclaved, followed by its use as a substrate for methanogenesis. This “swine feces supernatant medium” facilitates the cultivation of the microbes of the seed sludge, sampling of the digested liquid using a syringe, and subculturing of the digested liquid in a subsequent medium using a syringe. Through 15 subcultures, digested liquids with high and low methane production potential were obtained, which were named “H-DS” and “L-DS,” respectively. On the day 10 of cultivation, chemical oxygen demand (COD) of H-DS significantly decreased by 31% and that of L-DS did not differ significantly compared with that on the day 0 of cultivation. Acetic acid concentration of H-DS (1009 mg/L) was significantly lower than that of L-DS (2686 mg/L). These chemical characteristics indicate that organics decomposition in L-DS was not successful and suggest that H-DS has high relative abundance of bacteria decomposing organic matter and methanogen utilizing acetic acid compared with those in L-DS. Microbial community analysis revealed that Shannon index of H-DS was significantly higher than that of L-DS, and the relative abundance of acetogenic bacteria (e.g., Syntrophomonas ) and acetic acid-utilizing methanogen ( Methanosarcina ) in H-DS was significantly higher than that in L-DS. Thus, the high methane production potential of H-DS might be attributable to the smooth flow from acetogenesis to methanogenesis step in the methane fermentation, compared with the case of L-DS.