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Development of Industrial‐Medium‐Required Elimination of the 2,3‐Butanediol Fermentation Pathway To Maintain Ethanol Yield in an Ethanologenic Strain of Klebsiella oxytoca
Author(s) -
Wood Brent E.,
Yomano L. P.,
York S. W.,
Ingram L. O.
Publication year - 2005
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp050100e
Subject(s) - 2,3 butanediol , acetoin , klebsiella oxytoca , corn steep liquor , fermentation , chemistry , bioconversion , food science , ethanol , ethanol fuel , cellulosic ethanol , ethanol fermentation , yield (engineering) , biomass (ecology) , sorbitol , biochemistry , biofuel , microbiology and biotechnology , cellulose , biology , agronomy , materials science , escherichia coli , klebsiella pneumoniae , metallurgy , gene
Fermentation efficiency and nutrient costs are both significant factors in process economics for the microbial conversion of cellulosic biomass to commodity chemicals such as ethanol. In this study, we have developed a more industrial medium (OUM1) composed of 0.5% corn steep liquor (dry weight basis) supplemented with mineral salts (0.2%), urea (0.06%), and glucose (9%). Although the growth of strain P2 was vigorous in this medium, approximately 14% of substrate carbon was diverted into 2,3‐butanediol and acetoin under the low pH conditions needed for optimal cellulase activity during simultaneous saccharification. Deleting the central region of the budAB genes encoding α‐acetolactate synthase and α‐acetolactate decarboxylase eliminated the butanediol and acetoin coproducts and increased ethanol yields by 12%. In OUM1 medium at pH 5.2, strain BW21 produced over 4% ethanol in 48 h (0.47 g ethanol per g glucose). Average productivity (48 h), ethanol titer, and ethanol yield for BW21 in OUM1 medium (pH 5.2) exceeded that of the parent (strain P2) in rich laboratory medium (Luria broth).