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

Long-chain fatty\nacid (LCFA) degradation primarily involves several\nspecies of <i>Syntrophomonas</i> and hydrogenotrophic methanogens,\nconstituting the rate-limiting step in anaerobic digestion. It is\ncrucial to augment their abundance to enhance LCFA degradation. Utilizing\nmicrobial carriers presents an effective strategy to maintain the\nmicroorganisms on the surface and prevent their washout from the digester.\nIn this study, we aimed to identify a suitable microbial carrier with\na superior adsorption capacity for LCFA-degrading microorganisms.\nWe tested various polymers, poly­(vinyl alcohol) (PVA), polypropylene\n(PP), polyethylene glycol (PEG), and polyvinylidene chloride (PVDC),\nadding them to the sludge at the concentration of 28.25 g L<sup>–1</sup> and incubating with olive oil. The amplicon sequencing analysis\nrevealed that PVDC retained <i>Syntrophomonas</i> more abundantly\nthan 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\ntimes higher abundance on PVDC compared to the sludge. Further analysis\nindicated that not only these LCFA-degrading syntrophic microbial\ncommunities but also <i>Propionispira</i> and <i>Anaerosinus</i>, which are capable of lipid hydrolysis and glycerol degradation,\nbecame dominant on PVDC. Actually, chemical analysis confirmed that\nadding PVDC promoted the olive oil degradation. These results underscore\nthe potential of PVDC in promoting anaerobic LCFA degradation.