title: Inhibition of residual n-hexane in anaerobic digestion of lipid-extracted microalgal wastes and microbial community shift.
abstract: Converting lipid-extracted microalgal wastes to methane (CH4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C6H14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (∼10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH4 yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes.
authors.affiliation: Department of Civil and Environmental Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Korea.
authors.forename: Yeo-Myeong
authors.initials: YM
authors.lastname: Yun
authors.affiliation: Department of Civil and Environmental Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Korea.
authors.forename: Hang-Sik
authors.initials: HS
authors.lastname: Shin
authors.affiliation: Water Resources and Environment Research Department, Korea Institute of Civil Engineering and Building Technology, 283 Daehwa-dong, Ilsanseo-gu, Goyang-si, Gyeonggi-do, 411-712, Korea.
authors.forename: Chang-Kyu
authors.initials: CK
authors.lastname: Lee
authors.affiliation: Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 102 Gajeong-ro, Yuseong-gu, Daejeon, 305-343, Korea.
authors.forename: You-Kwan
authors.initials: YK
authors.lastname: Oh
authors.affiliation: Department of Environmental Engineering, Chonbuk National University, 567 Baekjedae-ro, Deokjin-gu, Jeonju, Jeonbuk, 561-756, Korea. hyunwoo@jbnu.ac.kr.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Kim
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000187:drug effects / Q000235:genetics; D056804:Biofuels / Q000032:analysis; D057919:Biological Oxygen Demand Analysis; D048408:Chlorella vulgaris / Q000737:chemistry*; D005285:Fermentation; D006586:Hexanes / Q000737:chemistry* / Q000494:pharmacology; D008055:Lipids; D008697:Methane / Q000032:analysis; D017017:Methanococcus / Q000187:drug effects / Q000235:genetics; D058086:Microalgae / Q000737:chemistry* / Q000378:metabolism; D058889:Molecular Typing; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D014866:Waste Products
chemical_list: D056804:Biofuels; D006586:Hexanes; D008055:Lipids; D012336:RNA, Ribosomal, 16S; D014866:Waste Products; C026385:n-hexane; D008697:Methane
keywords: Anaerobic digestion; Inhibition; Lipid-extracted microalgal wastes; Next-generation sequencing; n-Hexane