@article{202460f9a038470cb3374c2547872ec9,
title = "Increased anode respiration enhances utilization of short-chain fatty acid and lipid wet-extraction from Scenedesmus acutus biomass in electro-selective fermentation",
abstract = "Electro-selective fermentation (ESF) can improve lipid extraction from Scenedesmus acutus biomass using green solvents like hexane and 1:1 hexane: isopropanol, but accumulation of short-chain fatty acids (SCFAs) wastes useable electrons. To eliminate the electron loss, we designed a flat-plate microbial electrolytic cell (MEC) to have a large anode area for a biofilm of anode respiring bacteria (ARB) that oxidize the SCFAs and generate current that produces H2 gas at the cathode. In 9-day batch tests of ESF in the flat-plate MEC, 18% of the total electrons in the feeding biomass were scavenged by the ARB biofilm and converted to current, leaving minimal concentrations of SCFAs. Extraction with two solvents — 1:1 hexane:isopropanol and 100% hexane – was evaluated at the end of the 9-day experiments. 30% of the total lipids became hexane-extractable with ESF, compared to <1% in the feeding biomass. Furthermore, hexane had 100% selectivity towards saturated long-chain fatty acids (LCFAs), which are superior for biofuel production. Thus, ESF improved the quantity and quality of extractable FAME-based biofuel from S. acutus, while directing electron equivalents in SCFAs to current and H2 generation at the cathode.",
keywords = "Electro-selective fermentation, Lipids, Scenedesmus, Selectivity, Short-chain fatty acids, Solvents",
author = "Yuanzhe Liu and Lai, {Yen Jung Sean} and Rittmann, {Bruce E.}",
note = "Funding Information: This project is supported by the U.S. National Scientific Foundation (award number 1509933 ). We thank Dr. John McGowen at the Arizona Center of Algal Technology and Innovation (AzCATI) for providing the algal biomass, Dr. Everett Eustance for his excellence at maintaining Photo-Bio Reactors, Mr. David Lowry at the Electron microscopy facility of the School of Life Sciences at Arizona State University for his expertise at Transmission Electronic Microscopy, and Dr. Juan Maldonado Ortiz at the Center for Microbiome Sequencing for his expertise in gene amplification and sequencing. Funding Information: SCFA concentrations, expressed in mg COD/L, were monitored throughout the batch experiment and are summarized in Fig. 4, along with cumulative Coulombs collected. Acetate, propionate, butyrate, and valerate, which were the only significant SCFAs, increased and then decreased over time, although each with its own timing. Acetate reached its peak on day 1, ?150?mg COD/L; valerate reached its peak on the same day as acetate, ?220?mg COD/L. For propionate and butyrate, the peak concentrations were ?550 and ?390?mg COD/L, at days 2 and 5 respectively. The fast depletion of acetate supports that it was rapidly oxidized by ARB, a well-known phenomenon [22,36,37]. The slight and brief accumulation of propionate and butyrate implies that they also were substrates for the ARB ? fermenter syntrophic pair. Geobacter, a common ARB, cannot directly utilize butyrate [38], which support that butyrate was first fermented to acetate, then oxidized by ARB, leading to the observed low acetate concentration in the system.This project is supported by the U.S. National Scientific Foundation (award number 1509933). We thank Dr. John McGowen at the Arizona Center of Algal Technology and Innovation (AzCATI) for providing the algal biomass, Dr. Everett Eustance for his excellence at maintaining Photo-Bio Reactors, Mr. David Lowry at the Electron microscopy facility of the School of Life Sciences at Arizona State University for his expertise at Transmission Electronic Microscopy, and Dr. Juan Maldonado Ortiz at the Center for Microbiome Sequencing for his expertise in gene amplification and sequencing.",
year = "2020",
month = apr,
doi = "10.1016/j.renene.2019.10.043",
language = "English (US)",
volume = "148",
pages = "374--379",
journal = "Renewable Energy",
issn = "0960-1481",
publisher = "Elsevier BV",
}