Conversion of xylan to ethanol by ethanologenic strains of Escherichia coli and Klebsiella oxytoca

Journal Article · Wed Apr 01 04:00:00 EST 1992 · Applied and Environmental Microbiology; (United States)

OSTI ID:7042304

Burchhardt, G; Ingram, L O ^[1]

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1. Univ. of Florida, Gainesville (United States)

A two-stage process was evaluated for the fermentation of polymeric feedstocks to ethanol by a single, genetically engineered microorganism. The truncated xylanase gene (xynZ) from the thermophilic bacterium Clostridium thermocellum was fused with the N terminus of lacZ to eliminate secretory signals. This hybrid gene was expressed at high levels in ethanologenic strains of Escherichia coli KO11 and Klebsiella oxytoca M5A1(pLOI555). Large amounts of xylanase (25 to 93 mU/mg of cell protein) accumulated as intracellular products during ethanol production. Cells containing xylanase for saccharification. After cooling, the hydrolysate was fermented to ethanol with the same organism (30C), thereby replenishing the supply of xylanase for a subsequent saccharification. Recombinant E. coli metabolized only xylose, while recombinant K. oxytoca M5A1 metabolized xylose, xylobiose, and xylotriose but not xylotetrose. Derivatives of this latter organism produced large amounts of intracellular xylosidase, and the organism is presumed to transport both xylobiose and xylotriose for intracellular hydrolysis. By using recombinant M5A1, approximately 34% of the maximal theoretical yield of ethanol was obtained from xylan by this two-stage process. The yield appeared to be limited by the digestability of commercial xylan rather than by a lack of sufficient xylanase or by ethanol toxicity. In general form, this two-stage process, which uses a single, genetically engineered microorganism, should be applicable for the production of useful chemicals from a wide range of biomass polymers.

• OSTI ID: 7042304
• Journal Information: Applied and Environmental Microbiology; (United States), Journal Name: Applied and Environmental Microbiology; (United States) Vol. 58:4; ISSN 0099-2240; ISSN AEMID
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
090900* -- Biomass Fuels-- Processing-- (1990-)
ALCOHOLS
BACTERIA
BIOCONVERSION
BIOSYNTHESIS
BIOTECHNOLOGY
CARBOHYDRATES
CHEMICAL REACTIONS
CLOSTRIDIUM
CLOSTRIDIUM THERMOCELLUM
DECOMPOSITION
DNA
ENZYMES
ESCHERICHIA COLI
ETHANOL
FERMENTATION
GENETIC ENGINEERING
GLYCOSYL HYDROLASES
HEMICELLULOSE
HYDROLASES
HYDROLYSIS
HYDROXY COMPOUNDS
KLEBSIELLA
LYSIS
METABOLISM
MICROORGANISMS
NUCLEIC ACIDS
O-GLYCOSYL HYDROLASES
ORGANIC COMPOUNDS
POLYSACCHARIDES
PROTEINS
RECOMBINANT DNA
SACCHARIDES
SACCHARIFICATION
SOLVOLYSIS
SYNTHESIS
XYLANASE
XYLANS