title: Alcohol-to-acid ratio and substrate concentration affect product structure in chain elongation reactions initiated by unacclimatized inoculum.
abstract: The objective of the study was to investigate whether the ratio of ethanol to acetate affects yield and product structure in chain elongation initiated by unacclimatized mixed cultures. The effect of varying the substrate concentration, while maintaining the same ratio of alcohol to acid, was also investigated. With a high substrate concentration, an alcohol to acid ratio >2:1 provided sufficient electron donor capacity for the chain elongation reaction. With an ethanol to acetate ratio of 3:1 (300mM total carbon), the highest n-caproate concentration (3033±98mg/L) was achieved during the stable phase of the reaction. A lower substrate concentration (150mM total carbon) gave a lower yield of products and led to reduced carbon transformation efficiency compared with other reaction conditions. The use of unacclimatized inoculum in chain elongation can produce significant amounts of odd-carbon-number carboxylates as a result of protein hydrolysis.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuses, Tongji University, Shanghai 200092, China; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China.
authors.forename: Yuhao
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuses, Tongji University, Shanghai 200092, China; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China. Electronic address: lvfan.rhodea@tongji.edu.cn.
authors.forename: Fan
authors.initials: F
authors.lastname: Lü
authors.affiliation: Centre for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of PR China (MOHURD), China.
authors.forename: Liming
authors.initials: L
authors.lastname: Shao
authors.affiliation: Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China; Centre for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of PR China (MOHURD), China.
authors.forename: Pinjing
authors.initials: P
authors.lastname: He
mesh_terms: D000085:Acetates / Q000737:chemistry; D019149:Bioreactors; D002208:Caproates / Q000737:chemistry; D002244:Carbon / Q000737:chemistry / Q000378:metabolism; D002264:Carboxylic Acids / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis
chemical_list: D000085:Acetates; D002208:Caproates; D002264:Carboxylic Acids; C037652:hexanoic acid; D000431:Ethanol; D002244:Carbon
keywords: Medium-chain carboxylic acids (MCCAs); Odd-carbon-number carboxylates; n-Caproate; n-Caprylate; n-Heptanoate