Engineering Thermotolerant Biocatalysts for Biomass Conversion to Products Page: 3 of 109
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
The main objective of this study is to identify thermotolerant facultative anaerobic
bacteria that can ferment all the sugars that can be derived from lignocellulosic biomass
to ethanol at 50 C and pH 5.0 that has been reported to be near optimal for the activity of
commercial fungal cellulases being developed for simultaneous saccharification and
fermentation of cellulose to ethanol. Since such a bacterium has not been described in the
literature, we have embarked on isolating a bacterium from nature that can be engineered
to ferment the biomass-derived sugars to ethanol. From about 77 environmental samples
we have isolated bacteria that can grow both aerobically and anaerobically at 50 C and
pH 5.0 in media containing xylose as the primary carbon source. From a total of 380
bacterial isolates we have identified strains 17C5, 36D1 and P4-102B for further study
based on their growth and fermentation characteristics. Based on 16S rRNA(DNA)
sequence the three bacterial isolates (strains 17C5, 36D1 and P4-102B) were identified as
Bacillus coagulans that forms a diverse group of sporogenic lactic acid bacteria.
Task A. Physiological characterization of thermotolerant Bacillus coagulans
Bacillus coagulans strains 17C5, 36D1 and P4-102B fermented glucose, xylose,
cellobiose, sucrose, mannose, arabinose, galactose as well as other minor sugars that are
present in lignocellulosic biomass in both rich medium as well as in mineral salts medium
supplemented with corn steep liquor (0.5 % w/v). B. coagulans strains failed to grow in
mineral salts medium without organic supplements that can be met with corn steep liquor.
Metabolic information obtained from genome sequence and annotation being developed
as a part of this study is expected to provide information on the nutrient requirement
based on missing metabolic pathways.
The primary product of fermentation of B. coagulans was L(+)-lactic acid and the
optical purity of lactic acid was normally higher than 95% in the three isolates.
Depending on the growth condition, medium composition, etc., the optical purity of L(+)-
lactic acid in the fermentation broth reached 100%. Both strains 36D1 and P4-102B carry
a gene that encodes the lactate dehydrogenase (d-LDH) that catalyzes D(-)-lactic acid
production. However, this gene (d-ldh) appears to be inactive although upon cloning and
insertion into E. coli this d-LDH from B. coagulans catalyzed the production of D(-)-
lactic acid suggesting that the d-ldh gene is not expressed in B. coagulans. In addition to
lactic acid, B. coagulans also produced small amount of acetate, ethanol, formate and
succinate. Presence of formate in the fermentation broth suggests the presence of
pyruvate formate-lyase (PFL) activity in the cell. Formate production was higher during
xylose fermentation compared to glucose fermentation, as expected due to higher energy
demand during anaerobic growth on xylose.
Lactate yield from glucose during fermentation was higher than 85% for all the tested
isolates of this study. The lactate yield from the pentose sugar xylose was about 80-85%
for these isolates. This higher lactate to xylose ratio is different from the values reported
for pentose-fermenting lactic acid bacteria. These non-sporulating lactic acid bacteria,
such as Lactobacillus and Lactococcus, produce lactate and acetate in equimolar amounts
Here’s what’s next.
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
K. T. Shanmugam, L. O. Ingram and J. A. Maupin-Furlow. Engineering Thermotolerant Biocatalysts for Biomass Conversion to Products, report, May 20, 2010; United States. (https://digital.library.unt.edu/ark:/67531/metadc935535/m1/3/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.