Production of recombinant bacterial endoglucanase as a co-product with ethanol during fermentation using derivatives of Escherichia coli KO11
✍ Scribed by B. E. Wood; D. S. Beall; L. O. Ingram
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 288 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
This study demonstrates a new approach to reduce the amount of fungal cellulase required for the conversion of cellulose into ethanol. Escherichia coli KO11, a biocatalyst developed for the fermentation of hemicellulose syrups, was used to produce recombinant endoglucanase as a co-product with ethanol. Seven different bacterial genes were expressed from plasmids in KO11. All produced cell-associated endoglucanase activity. KO11(pLOI1620) containing Erwinia chrysanthemi celZ (EGZ) produced the highest activity, 3,200 IU endo- glucanase/L fermentation broth (assayed at pH 5.2 and 35°C). Recombinant EGZ was solubilized from harvested cells by treatment with dilute sodium dodecyl sulfate (12.5 mg/ml, 10 min, 50°C) and tested in fermentation experiments with commercial fungal cellulase (5 filter paper units/g cellulose) and purified cellulose (100 g/L). Using Klebsiella oxytoca P2 as the biocatalyst, fermentations supplemented with EGZ as a detergent-lysate of KO11(pLOI1620) produced 14%-24% more ethanol than control fermentations supplemented with a detergentlysate of KO11(pUC18). These results demonstrate that recombinant bacterial endoglucanase can function with fungal cellulase to increase ethanol yield during the simultaneous saccharification and fermentation of cellulose.