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Controlling Ethanol Use in Chain Elongation by CO2 Loading Rate

By M. Roghair, Tim Hoogstad, D.P.B.T.B. Strik, C.M. Plugge, P.H.A. Timmers, R.A. Weusthuis, M.E. Bruins and C.J.N. Buisman

Abstract

Chain elongation is an open-culture biotechnological<br/>process which converts volatile fatty acids (VFAs) into<br/>medium chain fatty acids (MCFAs) using ethanol and other<br/>reduced substrates. The objective of this study was to<br/>investigate the quantitative effect of CO2 loading rate on<br/>ethanol usages in a chain elongation process. We supplied<br/>different rates of CO2 to a continuously stirred anaerobic<br/>reactor, fed with ethanol and propionate. Ethanol was used to<br/>upgrade ethanol itself into caproate and to upgrade the<br/>supplied VFA (propionate) into heptanoate. A high CO2<br/>loading rate (2.5 LCO2·L−1·d−1) stimulated excessive ethanol<br/>oxidation (EEO; up to 29%) which resulted in a high caproate production (10.8 g·L−1·d−1). A low CO2 loading rate (0.5 LCO2·<br/>L−1·d−1) reduced EEO (16%) and caproate production (2.9 g·L−1·d−1). Heptanoate production by VFA upgrading remained<br/>constant (∼1.8 g·L−1·d−1) at CO2 loading rates higher than or equal to 1 LCO2·L−1·d−1. CO2 was likely essential for growth of<br/>chain elongating microorganisms while it also stimulated syntrophic ethanol oxidation. A high CO2 loading rate must be selected<br/>to upgrade ethanol (e.g., from lignocellulosic bioethanol) into MCFAs whereas lower CO2 loading rates must be selected to<br/>upgrade VFAs (e.g., from acidified organic residues) into MCFAs while minimizing use of costly ethanol

Topics: Sectie Milieutechnologie, Milieutechnologie, Biobased Chemistry and Technology, Biobased Chemistry and Technology, WIMEK, Laboratorium voor Microbiologie, Microbiologie, VLAG, Leerstoelgroep Bioprocestechnologie, Bioprocestechnologie, FBR Bioconversion, BBP Bioconversion, Sub-department of Environmental Technology, Environmental Technology, Biobased Chemistry and Technology, Biobased Chemistry and Technology, WIMEK, Microbiological Laboratory, Microbiology, VLAG, Bioprocess Engineering, Bioprocess Engineering, FBR Bioconversion, BBP Bioconversion
Year: 2018
DOI identifier: 10.1021/acs.est.7b04904
OAI identifier:
Provided by: NARCIS
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