Enrichment of a solventogenic anaerobic sludge converting carbon monoxide and syngas into acids and alcohols

• Published in: Bioresource technology 2019-01, Vol.272, p.130-136
• Main Authors: Chakraborty, Samayita, Rene, Eldon R., Lens, Piet N.L., Veiga, María C., Kennes, Christian
• Format: Article
• Language: English
• Subjects: 1-Butanol - metabolism; Acetic Acid - metabolism; Biomass; Bioreactors; Butanol; Butyrates - metabolism; Caproates - metabolism; Carbon Monoxide - metabolism; Ethanol; Ethanol - metabolism; Gases - metabolism; Hexanol; Sewage - microbiology; Solventogenesis; Volatile fatty acids
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2018.10.002

[Display omitted] •A rich medium (yeast extract) and high pH (≥6) favours biomass growth on C1-gases.•Mainly fatty acids (C2–C6) but also some alcohols accumulate during biomass growth.•Production of fatty acids stopped once biomass growth levelled off.•After reaching maximum biomass accumulation fatty acids were converted to alcohols. An anaerobic granular sludge was acclimatized to utilise CO in a continuously gas-fed stirred tank bioreactor by applying operating conditions expected to stimulate solventogenesis, i.e. the production of alcohols, and allowing to enrich for solventogenic populations. A cycle of high (6.2) and low (4.9) pH was applied in order to produce volatile fatty acids first at high pH, followed by their bioconversion into alcohols at low pH. The addition of yeast extract stimulated biomass growth, but not necessarily solventogenesis. The highest concentrations of metabolites achieved were 6.18 g/L acetic acid (30th day), 1.18 g/L butyric acid (28th day), and 0.423 g/L hexanoic acid (32nd day). Subsequently, acids were metabolized at lower pH, producing alcohols at concentrations of 11.1 g/L ethanol (43rd day), 1.8 g/L butanol (41st day) and 1.46 g/L hexanol (42nd day), confirming the successful enrichment strategy. Similarly, the enriched sludge could also convert syngas into acids and alcohols.