title: In situ esterification and extractive fermentation for butyl butyrate production with Clostridium tyrobutyricum.
abstract: Butyl butyrate (BB) is a valuable chemical that can be used as flavor, fragrance, extractant, and so on in various industries. Meanwhile, BB can also be used as a fuel source with excellent compatibility as gasoline, aviation kerosene, and diesel components. The conventional industrial production of BB is highly energy-consuming and generates various environmental pollutants. Recently, there have been tremendous interests in producing BB from renewable resources through biological routes. In this study, based on the fermentation using the hyper-butyrate producing strain Clostridium tyrobutyricum ATCC 25755, efficient BB production through in situ esterification was achieved by supplementation of lipase and butanol into the fermentation. Three commercially available lipases were assessed and the one from Candida sp. (recombinant, expressed in Aspergillus niger) was identified with highest catalytic activity for BB production. Various conditions that might affect BB production in the fermentation have been further evaluated, including the extractant type, enzyme loading, agitation, pH, and butanol supplementation strategy. Under the optimized conditions (5.0 g L-1of enzyme loading, pH at 5.5, butanol kept at 10.0 g L-1), 34.7 g L-1BB was obtained with complete consumption of 50 g L-1glucose as the starting substrate. To our best knowledge, the BB production achieved in this study is the highest among the ever reported from the batch fermentation process. Our results demonstrated an excellent biological platform for renewable BB production from low-value carbon sources. Biotechnol. Bioeng. 2017;114: 1428-1437. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Biosystems Engineering, Auburn University, 215 Tom E. Corley Building, Auburn, Alabama 36849.
authors.forename: Zhong-Tian
authors.initials: ZT
authors.lastname: Zhang
authors.affiliation: Department of Biosystems Engineering, Auburn University, 215 Tom E. Corley Building, Auburn, Alabama 36849.|Center for Bioenergy and Bioproducts, Auburn University, Auburn, Alabama.
authors.forename: Steven
authors.initials: S
authors.lastname: Taylor
authors.affiliation: Department of Biosystems Engineering, Auburn University, 215 Tom E. Corley Building, Auburn, Alabama 36849.|Center for Bioenergy and Bioproducts, Auburn University, Auburn, Alabama.
authors.forename: Yi
authors.identifier: 0000-0002-0192-3195
authors.initials: Y
authors.lastname: Wang
mesh_terms: D061249:Batch Cell Culture Techniques / Q000379:methods; D019149:Bioreactors / Q000382:microbiology*; D000440:Butanols / Q000378:metabolism*; D002087:Butyrates / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D048014:Clostridium tyrobutyricum / Q000502:physiology*; D003247:Conservation of Natural Resources / Q000379:methods; D004951:Esterification / Q000502:physiology; D005285:Fermentation; D008049:Lipase / Q000378:metabolism*; D059625:Liquid-Liquid Extraction / Q000379:methods
chemical_list: D000440:Butanols; D002087:Butyrates; C022793:n-butyl n-butyrate; D008049:Lipase
keywords: butyl butyrate; butyrate; equilibrium constant; esterification; extractive fermentation Clostridium tyrobutyricum