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One-step production of lactate from cellulose as the sole carbon source without any other organic nutrient by recombinant cellulolytic Bacillus subtilis

Paper ID Volume ID Publish Year Pages File Format Full-Text
31633 44826 2011 9 PDF Available
Title
One-step production of lactate from cellulose as the sole carbon source without any other organic nutrient by recombinant cellulolytic Bacillus subtilis
Abstract

Although intensive efforts have been made to create recombinant cellulolytic microorganisms, real recombinant cellulose-utilizing microorganisms that can produce sufficient secretory active cellulase, hydrolyze cellulose, and utilize released soluble sugars for supporting both cell growth and cellulase synthesis without any other organic nutrient (e.g., yeast extract, peptone, amino acids), are not available. Here we demonstrated that over-expression of Bacillus subtilis endoglucanase BsCel5 enabled B. subtilis to grow on solid cellulosic materials as the sole carbon source for the first time. Furthermore, two-round directed evolution was conducted to increase specific activity of BsCel5 on regenerated amorphous cellulose (RAC) and enhance its expression/secretion level in B. subtilis. To increase lactate yield, the alpha-acetolactate synthase gene (alsS) in the 2,3-butanediol pathway was knocked out. In the chemically defined minimal M9/RAC medium, B. subtilis XZ7(pBscel5-MT2C) strain (ΔalsS), which expressed a BsCel5 mutant MT2C, was able to hydrolyze RAC with cellulose digestibility of 74% and produced about 3.1 g/L lactate with a yield of 60% of the theoretical maximum. When 0.1% (w/v) yeast extract was added in the M9/RAC medium, cellulose digestibility and lactate yield were enhanced to 92% and 63% of the theoretical maximum, respectively. The recombinant industrially safe cellulolytic B. subtilis would be a promising consolidated bioprocessing platform for low-cost production of biocommodities from cellulosic materials.

Keywords
Bacillus subtilis; Cellulase engineering; Consolidated bioprocessing; Endoglucanase; Lactate; Metabolic engineering; Directed evolution
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One-step production of lactate from cellulose as the sole carbon source without any other organic nutrient by recombinant cellulolytic Bacillus subtilis
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Publisher
Database: Elsevier - ScienceDirect
Journal: Metabolic Engineering - Volume 13, Issue 4, July 2011, Pages 364–372
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us