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Abstract (Expand)

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(-1) of enzyme loading, pH at 5.5, butanol kept at 10.0 g L(-1) ), 34.7 g L(-1) BB was obtained with complete consumption of 50 g L(-1) glucose 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. (c) 2017 Wiley Periodicals, Inc.

Authors: Z. T. Zhang, S. Taylor, Y. Wang

Date Published: No date defined

Publication Type: Not specified

Abstract (Expand)

The recovery of 1-butanol from fermentation broth is energy-intensive since typical concentrations in fermentation broth are below 20 g L(-1). To prevent butanol inhibition and high downstream processing costs, we aimed at producing butyl esters instead of 1-butanol. It is shown that it is possible to perform simultaneously clostridial fermentation, esterification of the formed butanol to butyl butyrate, and extraction of this ester by hexadecane. The very high partition coefficient of butyl butyrate pulls the esterification towards the product side even at fermentation pH and relatively low butanol concentrations. The hexadecane extractant is a model diesel compound and is nontoxic to the cells. If butyl butyrate enriched diesel can directly be used as car fuel, no product recovery is required. A proof-of-principle experiment for the one-pot bio-ester production from glucose led to 5 g L(-1) butyl butyrate in the hexadecane phase. The principle may be extended to a wide range of esters, especially to longer chain ones.

Authors: C. van den Berg, A. S. Heeres, L. A. van der Wielen, A. J. Straathof

Date Published: No date defined

Publication Type: Not specified

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