Tracking the cellulolytic activity of Clostridium thermocellum biofilms

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dc.contributor.authorDumitrache, Alexandruen_ZA
dc.contributor.authorWolfaardt, Gideon M.en_ZA
dc.contributor.authorAllen, David Granten_ZA
dc.contributor.authorLiss, Steven N.en_ZA
dc.contributor.authorLynd, Lee R.en_ZA
dc.date.accessioned2015-08-12T12:48:14Z
dc.date.available2015-08-12T12:48:14Z
dc.date.issued2013-11-29
dc.descriptionThe original publication is available at https://biotechnologyforbiofuels.biomedcentral.com/en
dc.description.abstractBackground: Microbial cellulose conversion by Clostridium thermocellum 27405 occurs predominantly through the activity of substrate-adherent bacteria organized in thin, primarily single cell-layered biofilms. The importance of cellulosic surface exposure to microbial hydrolysis has received little attention despite its implied impact on conversion kinetics. Results: We showed the spatial heterogeneity of fiber distribution in pure cellulosic sheets, which made direct measurements of biofilm colonization and surface penetration impossible. Therefore, we utilized on-line measurements of carbon dioxide (CO2) production in continuous-flow reactors, in conjunction with confocal imaging, to observe patterns of biofilm invasion and to indirectly estimate microbial accessibility to the substrate’s surface and the resulting limitations on conversion kinetics. A strong positive correlation was found between cellulose consumption and CO2 production (R2 = 0.996) and between surface area and maximum biofilm activity (R2 = 0.981). We observed an initial biofilm development rate (0.46 h-1, 0.34 h-1 and 0.33 h-1) on Whatman sheets (#1, #598 and #3, respectively) that stabilized when the accessible surface was maximally colonized. The results suggest that cellulose conversion kinetics is initially subject to a microbial limitation period where the substrate is in excess, followed by a substrate limitation period where cellular mass, in the form of biofilms, is not limiting. Accessible surface area acts as an important determinant of the respective lengths of these two distinct periods. At end-point fermentation, all sheets were digested predominantly under substrate accessibility limitations (e.g., up to 81% of total CO2 production for Whatman #1). Integration of CO2 production rates over time showed Whatman #3 underwent the fastest conversion efficiency under microbial limitation, suggestive of best biofilm penetration, while Whatman #1 exhibited the least recalcitrance and the faster degradation during the substrate limitation period. Conclusion: The results showed that the specific biofilm development rate of cellulolytic bacteria such as C. thermocellum has a notable effect on overall reactor kinetics during the period of microbial limitation, when ca. 20% of cellulose conversion occurs. The study further demonstrated the utility of on-line CO2 measurements as a method to assess biofilm development and substrate digestibility pertaining to microbial solubilization of cellulose, which is relevant when considering feedstock pre-treatment options. en_ZA
dc.description.urihttps://biotechnologyforbiofuels.biomedcentral.com/articles/10.1186/1754-6834-6-175
dc.description.versionPublishers versionen
dc.format.extent13 pages : illustrationsen_ZA
dc.identifier.citationDumitrache, A, Wolfaardts, GM, Allen, DG, LIss, SN & Lynd, LR. 2013. Tracking the cellulolytic activity of Clostridium thermocellum biofilms. Biotechnology for Biofuels, 6:175, https://doi.org/10.1186/1754-6834-6-175.en
dc.identifier.issn1754-6834 (online)en_ZA
dc.identifier.otherdoi:10.1186/1754-6834-6-175en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/97385
dc.language.isoen_ZAen_ZA
dc.publisherBioMed Centralen_ZA
dc.rights.holderAuthors retain copyrighten_ZA
dc.subject.lcshBiofilms -- Analysisen_ZA
dc.subject.lcshClostridium thermocellumen_ZA
dc.subject.lcshCellulose -- Microbiologyen_ZA
dc.subject.lcshBiofilms -- Measurementen_ZA
dc.subject.lcshBiofilm kineticsen_ZA
dc.subject.lcshCarbon dioxide productionen_ZA
dc.titleTracking the cellulolytic activity of Clostridium thermocellum biofilmsen_ZA
dc.typeArticleen_ZA
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