Abstract
Size distributions and glucose and pH profiles of aggregates of the d-(-)-lactic acid-producing organism Bacillus laevolacticus were measured. The organisms were grown in continuous culture with a medium glucose concentration of either 280 or 110 mM. A maximal aggregate diameter of 2.2 mm, with a Sauter mean of 1.46 mm, was determined for the former culture condition, whereas aggregates from a culture with 110 mM glucose input had a maximal diameter of 1.9 mm (Sauter mean of 1.07 mm). A pH gradient of approximately 2 U was observed for large aggregates (above 1.5 mm). In smaller aggregates (0.75 mm), the pH value in the interior part was approximately 0.4 U lower than that in the culture fluid. It could be concluded that, in cultures with the high glucose input, lactic acid accumulated within the aggregates to such an extent that metabolism in the central region of the larger aggregates could not proceed further. In these cultures, approximately 90% of the total biomass was active. In aggregates from cultures with a low glucose input, glucose only partly penetrated the larger-sized aggregates, and the activity of this culture was reduced to approximately 70% of the biomass. These aggregates were found to decrease in size after prolonged periods of cultivation. It is suggested that this is caused by glucose depletion in the interior of the aggregates. It is concluded that the availability of glucose is an important factor in determining the size of aggregates of B. laevolacticus.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Beeftink H. H., Staugaard P. Structure and dynamics of anaerobic bacterial aggregates in a gas-lift reactor. Appl Environ Microbiol. 1986 Nov;52(5):1139–1146. doi: 10.1128/aem.52.5.1139-1146.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Costerton J. W., Irvin R. T., Cheng K. J. The bacterial glycocalyx in nature and disease. Annu Rev Microbiol. 1981;35:299–324. doi: 10.1146/annurev.mi.35.100181.001503. [DOI] [PubMed] [Google Scholar]
- Cronenberg C. C., van den Heuvel J. C. Determination of glucose diffusion coefficients in biofilms with micro-electrodes. Biosens Bioelectron. 1991;6(3):255–262. doi: 10.1016/0956-5663(91)80011-l. [DOI] [PubMed] [Google Scholar]
- Herbert D., Phipps P. J., Tempest D. W. The chemostat: design and instrumentation. Lab Pract. 1965 Oct;14(10):1150–1161. [PubMed] [Google Scholar]