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Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation
Dissertation (MEng)--University of Pretoria, 2013.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2014
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| _version_ | 1867613723142651904 |
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| access_status_str | Open Access |
| author2 | Nicol, Willie |
| author_browse | Nicol, Willie |
| author_facet | Nicol, Willie |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/40826 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:40:40.528Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/40826 Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation Nicol, Willie michael.bradfield@tuks.co.za Bradfield, M.F.A. (Michael Ford Alexander) Actinobacillus succinogenes Biofilm Corn steep liquor Metabolic flux analysis Succinic acid UCTD Dissertation (MEng)--University of Pretoria, 2013. Continuous fermentations were performed in a novel external-recycle, biofilm reactor using D-glucose and CO2 as carbon substrates. Corn steep liquor (CSL) and yeast extract (YE) served as nitrogen sources. In anaerobic fermentations using medium containing CSL and YE, succinic acid (SA) yields were found to be an increasing function of glucose consumption. The ratio of SA to the major by-product, acetic acid (YAASA), increased from 2.4 g g-1 at a glucose consumption of 15 g L-1, to 5.7 g g-1 at a glucose consumption of 46 g L-1. For medium containing no CSL, YAASA remained near 1.97 g g-1, exceeding this for cases where biofilm grown on CSL-containing medium was present. The ratio of formic acid to acetic acid (YAAFA), for CSL-containing medium, decreased from an equimolar value (0.77 g g-1) at a glucose consumption of 10 g L-1 to zero at 46 g L-1 glucose consumed. In contrast, YAAFA for YE-only medium remained at 0.77 g g-1. Therefore, pyruvate was metabolised solely by pyruvate-formate lyase when no CSL was present. The highest SA yield obtained on glucose, SA titre and SA productivity were 0.91 g g-1, 48.5 g L-1 and 9.4 g L-1 h-1, respectively, all for medium containing CSL. Medium that included CSL significantly outperformed medium that excluded CSL, achieving 64%, 21% and 203% greater SA titres, yields on glucose and productivities respectively. Metabolic flux analyses based on the established C3 and C4 metabolic pathways of Actinobacillus succinogenes revealed that the increase in YAASA, for CSL-containing fermentations, could not be attributed to the decrease in formate and biomass formation, and that an additional source of reducing power was present. The fraction of reducing power (NADH) unaccounted for increased with glucose consumption, suggesting that the maintenance or non-growth metabolism encountered at higher SA titres differs from the growth metabolism. It is postulated that the additional reducing power originates from an active pentose phosphate pathway in non-growing cells or from an undetected component(s) in the fermentation medium. No major metabolic flux variations were found in fermentations that excluded CSL. gm2014 Chemical Engineering unrestricted 2014-07-17T12:10:27Z 2014-07-17T12:10:27Z 2014-04-08 2013 Dissertation Bradfield, MFA 2013, Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/40826> E14/4/286/gm http://hdl.handle.net/2263/40826 en © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Actinobacillus succinogenes Biofilm Corn steep liquor Metabolic flux analysis Succinic acid UCTD Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title | Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title_full | Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title_fullStr | Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title_full_unstemmed | Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title_short | Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation |
| title_sort | continuous production of succinic acid by actinobacillus succinogenes steady state metabolic flux variation |
| topic | Actinobacillus succinogenes Biofilm Corn steep liquor Metabolic flux analysis Succinic acid UCTD |
| url | http://hdl.handle.net/2263/40826 |