Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Effect of nutrient limitation in chemostat cultures on amino acid excretion in Clostridium thermocellum
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
2019 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Introduction: Clostridium thermocellum is considered a model organism forconsolidated bioprocessing, due to its ability to hydrolyze lignocellulosicbiomass more efficiently than many other organisms and to produce ethanol.In order to meet the industrial requirements of ethanol yield and titer, metabolicengineering efforts have been made resulting in a strain that successfullydisplays increased ethanol yield with reduced amount of some byproducts.However, the ethanol yield in this engineered strain still does not meet theindustrial requirements and significant amounts of amino acids are stillproduced. To attempt to decrease the level of amino acid excretion intended toimprove the ethanol yield in C. thermocellum, it is essential to understand itsmetabolism and how it is affected by different cultivation conditions and mediumcompositions. This study aimed to gain an insight in how carbon- and nitrogenlimitation affect amino acid excretion in C. thermocellum, with the hypothesisthat excess of carbon and nitrogen yields more amino acid excretion.

Methods: Mass-balance based calculations of rates and yields were used toanalyze the metabolism of a wild-type of C. thermocellum (DSM 1313) grownanaerobically in carbon- or nitrogen-limiting chemostats. For this, Low-Carbonmedium containing, respectively, cellobiose (5 g/L) and urea (0.15 g/L) as thelimiting nutrient was used. Both cultivations were performed at 55 °C, pH 7.0and 400 RPM shaking at a dilution rate of 0.1 h-1.

Conclusion:  Considering yields of total amino acids excreted in bothlimitations, it was hypothesized that C. thermocellum exploited the amino acidexcretion to maintain carbon balance around the pyruvate node caused byexcess of the carbon. Based on yield of valine excreted in particular, it washypothesized that amino acid excretion was used to maintain redox balance inthe metabolism of C. thermocellum, where malate shunt could play a major role.However, results of the Carbon-limitation did not allow any conclusion ofnitrogen excess having an effect on amino acid excretion in C. thermocellum.

Place, publisher, year, edition, pages
2019. , p. 27
Keywords [en]
Biotechnology, ethanol, Clostridium, chemostat, nitrogen
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-259545OAI: oai:DiVA.org:kth-259545DiVA, id: diva2:1352060
Educational program
Master of Science in Engineering - Biotechnology
Supervisors
Examiners
Available from: 2019-09-19 Created: 2019-09-17 Last updated: 2019-09-19Bibliographically approved

Open Access in DiVA

fulltext(695 kB)2 downloads
File information
File name FULLTEXT01.pdfFile size 695 kBChecksum SHA-512
742205aaa44f9979295949402923f5aadca9d8cf9c9df2f9545fc07376f5077614f646498691ea7942e5cd3ef6cad0cb86d50abc4c4ff08d00e41e905bc83ec6
Type fulltextMimetype application/pdf

By organisation
Industrial Biotechnology
Industrial Biotechnology

Search outside of DiVA

GoogleGoogle Scholar
Total: 2 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 14 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf