Discovery of a Microbial Carrier with High Adsorption Affinity for Syntrophic Long-Chain Fatty Acid-Degrading Microorganisms

Long-chain fatty
acid (LCFA) degradation primarily involves several
species of Syntrophomonas and hydrogenotrophic methanogens,
constituting the rate-limiting step in anaerobic digestion. It is
crucial to augment their abundance to enhance LCFA degradation. Utilizing
microbial carriers presents an effective strategy to maintain the
microorganisms on the surface and prevent their washout from the digester.
In this study, we aimed to identify a suitable microbial carrier with
a superior adsorption capacity for LCFA-degrading microorganisms.
We tested various polymers, poly­(vinyl alcohol) (PVA), polypropylene
(PP), polyethylene glycol (PEG), and polyvinylidene chloride (PVDC),
adding them to the sludge at the concentration of 28.25 g L–1 and incubating with olive oil. The amplicon sequencing analysis
revealed that PVDC retained Syntrophomonas more abundantly
than the other polymers. Remarkably, PVDC predominantly adsorbed LCFA-degrading S. sapovorans and S. zehnderi, whereas medium- to short-chain fatty acid-degrading S. wolfei was abundant in the sludge. Moreover, hydrogenotrophic Methanospirillum hungatei was detected at 2.3–9.5
times higher abundance on PVDC compared to the sludge. Further analysis
indicated that not only these LCFA-degrading syntrophic microbial
communities but also Propionispira and Anaerosinus, which are capable of lipid hydrolysis and glycerol degradation,
became dominant on PVDC. Actually, chemical analysis confirmed that
adding PVDC promoted the olive oil degradation. These results underscore
the potential of PVDC in promoting anaerobic LCFA degradation.