Saccharification and fermentation of Sugar Cane bagasse by Klebsiella oxytoca P2 containing chromosomally integrated genes encoding the Zymomonas mobilis ethanol pathway

Abstract

Pretreatment of sugar cane bagasse is essential for a simultaneous saccharification and fermentation (SSF) process which uses recombinant Klebsiella oxytoca strain P2 and Genencor Spezyme CE. Strain P2 has been genetically engineered to express Zymomonas mobilis genes encoding the ethanol pathway and retains the native ability to transport and metabolize cellobiose (minimizing the need for extracellular cellobiase). In SSF studies with this organism, both the rate of ethanol production and ethanol yield were limited by saccharification at 10 and 20 filter papaer units (FPU) g(-1) acid-treated bagasse. Dilute slurries of biomass were converted to ethanol more efficiently (over 72% of theoretical yield) in simple batch fermentations than slurries containing high solids albeit with the production of lower levels of ethanol. With high solids (i.e., 160 g acid-treated bagasse L(-1)), a combination of 20 FPU cellulase g(-1) bagasse, preincubation under saccharification conditions, and additional grinding (to reduce particle size) were required to produce ca. 40 g ethanol L(-1). Alternatively, almost 40 g ethanol L(-1) was produced with 10 FPU cellulase g(-1) bagasse by incorporating a second saccharification step (no further enzyme addition) followed by a second inoculation and short fermentation. In this way, a theoretical ethanol yield of over 70% was achieved with the production of 20 g ethanol 800 FPU(-1) of commercial cellulase. (c) 1994 John Wiley & Sons, Inc.

Ethanolic fermentation of sucrose, sugarcane juice and molasses by Escherichia coli strain ko11 and Klebsiella oxytoca strain P2

“…Ethanol is a pure substance of known composition, whereas gasoline is a mixture of different compounds. Alcohol is also a more secure energy source because it is renewable (11,23) and can be produced anywhere in the world from biomass.…”

“…The efficiency of KO11 and P2 in conversion of various substrates to ethanol, including simple sugars (5,16,21,22,29), starch (15), and hydrolyzed lignocellulose (2,3,11,12,13) has been determined. In this study we examined growth and ethanol fermentation of sucrose, sugarcane juice and molasses by these recombinants.…”

Advances in consolidated bioprocessing systems for bioethanol and butanol production from biomass: a comprehensive review

“…Previously, recombinant strains of K. oxytoca containing Z. mobilis pdc (pyruvate decarboxylase) and adhB (alcohol dehydrogenase) genes have been developed. These strains are able to direct the metabolism of pyruvate to ethanol, but for efficient ethanol production they need cellulase to be added to the cellulosic materials, which imposes additional cost on the ethanol production process (Ohta et al, 1991b;Doran and Ingram, 1993;Bothast et al, 1994;Doran et al, 1994;Brooks and . Ingram, 1995;Golias et al, 2002).…”

Thermodynamic Characterization of <i>Saccharomyces cerevisiae</i> Catalyzed Fermentation of Cane Sugar

“…The desire to harness other primary sources such as sugars from varying effluents which are viably recoverable and fermented to primary alcohols is regaining global interest. Primary alcohols can easily be blended with gasoline as gasohol or combusted directly to power piston engines [13]. Moreover there is growing concern about depleting reserves of fossil fuels as well as global concern for environmental degradation attributed to CO x , SO x and NO x released when fossil fuels are combusted.…”