http://hdl.handle.net/10204/891 2013-06-19T09:25:19Z http://hdl.handle.net/10204/6697 Title: The soil and plant determinants of community structures of the dominant actinobacteria in Marion Island terrestrial habitats, Sub-Antarctica Authors: Sanyika, TW; Stafford, W; Cowan, DA Abstract: Marion Island is a Sub-Antarctic island made up of distinct ecological habitats based on soil physiochemical, plant cover and physical characteristics. The microbial diversity and ecological determinants in this harsh Sub-Antarctic environment are largely uncharacterized. Actinobacteria have diverse ecological functions related to soil and plant functioning. This study was aimed at characterizing the diversity and community structures of the dominant actinobacteria in the distinct habitats and to identify their determinant soil and plant characteristics. Using the 16S rRNA gene, the denaturing gradient gel electrophoresis patterns and clone library diversity were correlated with the soil and plant characteristics. Multivariate statistical methods were also used to identify determinant soil and plant characteristics. Salinity and pH were the most important soil determinants, and a number of important site-specific plant species may have been important. The Coastal Fellfield Habitat was dominated by sequences of the suborders Micrococcineae (44%) and Propionibacterineae (18%), with salinity identified as the principal determinant. The Cotula Herbfield Habitat was dominated by Frankineae (37%) and Streptosporangineae (38%), which were correlated with organic nutrient concentrations. The Wet Mire Habitat was dominated by Acidimicrobineae (61%), with moisture and organic carbon content as principal components. Culture-dependent studies were complementary to culture-independent studies with the majority of actinobacteria isolated not identified in 16S rRNA gene clone libraries. This study demonstrates how the soil physiochemical characteristics and plant species independently determine the community structures of the dominant actinobacteria in distinct ecological habitats. These factors subsequently influence their ecological adaptation, roles and functions. Description: Copyright: 2012 Springer Verlag. This is an ABSTRACT ONLY. The definitive version is published in Polar Biology, vol. 35(8), pp 1129-1141 2012-08-01T00:00:00Z http://hdl.handle.net/10204/6497 Title: Enzymatic synthesis of 5-methyluridine by transglycosylation of guanosine and thymine Authors: Visser, DF; Gordon, GER; Bode, ML; Mathiba, K; Brady, D Abstract: 5-Methyluridine (5-MU) is an intermediate in the synthesis of ß-thymidine and the antiretroviral drugs stavudine (d4T) and zidovudine (AZT)1-3. The enzymatic preparation of 5-MU involves transglycosylation4-6 and avoids the formation of unwanted isomers. The overall transglycosylation reaction effectively converts one nucleoside into another through exchange of the heterocyclic base in the presence of nucleoside phosphorylases. Description: Copyright: 2012 John Wiley & Sons. This is an ABSTRACT ONLY. 2012-05-01T00:00:00Z http://hdl.handle.net/10204/6370 Title: Immobilisation and characterisation of biocatalytic co-factor recycling enzymes, glucose dehydrogenase and NADH oxidase, on aldehyde functional ReSynTM polymer microspheres Authors: Twala, BV; Sewell, BT; Jordaan, J Abstract: The use of enzymes in industrial applications is limited by their instability, cost and difficulty in their recovery and re-use. Immobilisation is a technique which has been shown to alleviate these limitations in biocatalysis. Here we describe the immobilisation of two biocatalytically relevant co-factor recycling enzymes, glucose dehydrogenase (GDH) and NADH oxidase (NOD) on aldehyde functional ReSynTM polymer microspheres with varying functional group densities. The successful immobilisation of the enzymes on this new high capacity microsphere technology resulted in the maintenance of activity of 40% for GDH and a maximum of 15.4% for NOD. The microsphere variant with highest functional group density of ~3500 mol g-1 displayed the highest specific activity for the immobilisation of both enzymes at 33.22 U mg-1 and 6.75 U mg-1 for GDH and NOD with respective loading capacities of 51% (0.51 mg mg-1) and 129% (1.29 mg mg-1). The immobilised GDH further displayed improved activity in the acidic pH range. Both enzymes displayed improved pH and thermal stability with the most pronounced thermal stability for GDH displayed on ReSynTM A during temperature incubation at 65 C with a 13.59 fold increase, and NOD with a 2.25-fold improvement at 45 C on the same microsphere variant. An important finding is the suitability of the microspheres for stabilisation of the multimeric protein GDH. Description: Copyright: 2012 Elsevier. This is a pre-print version of the work. The definitive version is published in Enzyme and Microbial Technology, Vol. 50, pp 331-336. 2012-03-01T00:00:00Z http://hdl.handle.net/10204/6212 Title: Isolation and screening of microorganisms from a gari fermentation process for starter culture development Authors: Edward, VA; Egounlety, M; Huch, M; Van Zyl, PJ; Singh, S; Nesengani, ND; Haakuria, VM; Franz, CMAP Abstract: Cassava (Manihot esculenta Crantz), is used for the production of a variety of West African foods and ranks fourth in the list of major crops in developing countries after rice, wheat and maize. Gari is one of the most popular foods produced from cassava. Cassava may contain high levels of linamarin, a cyanogenic glucoside, which in its natural state is toxic to man. Therefore, some processing methods that can enhance the detoxification of cassava and lead to the improvement of the quality and hygienic safety of the food are vitally important for less toxic products to be obtained. Quality, safety and acceptability of traditional fermented foods may be improved through the use of starter cultures. There has been a trend recently to isolate wild-type strains from traditional products for use as starter cultures in food fermentation. A total of 74 bacterial strains and 21 yeast strains were isolated from a cassava mash fermentation process in a rural village in Benin, West Africa. These strains were assessed, together with 26 strains isolated at the Council for Scientific and Industrial Research (CSIR) from cassava samples sent from Benin previously, for phenotypic and technological properties. 24 presumptive lactic acid bacteria (LAB) were selected for further phenotypic, genotypic and technological characterization. Description: Copyright: 2012 Academic Journals 2012-08-01T00:00:00Z