Thesis (M.Sc. (Microbiology)) --University of Limpopo, 2011 / Pterocarpus angolensis seed lectin (PAL), a 28 kDa non glycosylated protein, was initially successfully cloned and expressed in E. coli for ease of high protein production. It was discovered, however, as in similar studies that the recombinant PAL yield in E. coli is low and localized intracellularly. This makes extraction even more difficult because most of the protein is lost either when the cell undergoes lysing or when there is incomplete extraction. As a result of the low yields in E. coli, expression vectors were constructed for pal expression in S. cerevisiae, Y. lipolytica and A. niger. Colony PCR of S. cerevisiae transformants confirmed the presence of pal gene whilst sequencing revealed a 66% homology to native PAL. Expression of recombinant PAL in S. cerevisiae, which was expected to be intracellular, was doubtfully unsuccessful since no signal was detected following Western blot analysis. A pBARMTE1-pal expression vector was successfully constructed and could be used for expression studies in Aspergillus niger, however, it was not used in this study. A pal gene whose codons were optimized for Y. lipolytica was synthesized and successfully cloned and expressed in Y. lipolytica. Gene sequence alignment of native pal and the codon optimized pal showed 81% homology whilst the amino acid alignment showed 100% homology. A 31 kDa, recombinant PAL was successfully expressed in Y. lipolytica. The recombinant PAL was approximately 3 kDa larger than native PAL. It was established that this is due to glycosylation of the recombinant PAL. This recombinant protein was found to be more thermostable than native PAL since it demonstrated haemagglutination activity after 10 minutes of exposure in a boiling water bath and only lost activity after 2 hours of exposure to boiling. This study succeeded in producing a more stable extracellular recombinant PAL which demonstrated biochemical activity that was largely similar to that of native PAL but only differed in carbohydrate specificity and haemagglutinating strengths. / Flemish Interuniversity Council (VLIR-UOS)-Own Initiative Project,the SARBIO- South African Regional Co-operation in Biochemistry, Molecular Biology and Biotechnology, the (CSIR) Council for Scientific and Industrial Research,the (NRF) National Research Foundation,(TBI) The Biovac Institute Foundation, and the (SIDA) Swedish International Agency

Thesis (MScFor)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Kiaat trees in Namibia are threatened by unsustainable harvesting practice. This study’s aim was to estimate the total value of an average Kiaat tree selected for harvesting with a focus on current timber use value, value of an optimally utilised tree, carbon value, and alternative uses of Kiaat trees. To accomplish this aim, the following specific objectives were set: (1) to estimate the total tree volume and optimum utilisable timber volume of an average Kiaat tree; (2) to estimate the amount and value of carbon stored in the above-ground parts of an average Kiaat tree; (3) to determine timber utilisation levels; and (4) to identify alternative use options to reduce timber losses of Kiaat trees. Previous studies on Kiaat in Namibia and elsewhere focused on growth, development and socio-economical aspects of Kiaat trees. A combination of a socio-economic survey and tree volumes and biomass determination was used to collect data. The survey entailed Kiaat products assessment and face-to-face personal interviews with known key-informants in and around Rundu. Loggers with permits to harvest Kiaat trees were asked to harvest 40 Kiaat trees and data collected from each tree before and after felling included: lower-stem diameter, diameter at breast height (DBH), upper-stem diameter, stem length, stump height, recovered merchantable logs lengths and lower-and-upper diameters and lengths of branches greater than 10 cm in diameter. All canopy parts smaller than 10 cm in diameter were directly weighed, sampled and oven-dried at 105°C until constant weight. Volume of different tree parts was calculated and in combination with basic wood density used to calculate the biomass. It was established that a typically harvested Kiaat tree had an above-ground dry volume of 1.63 m3, of which 1.34 m3 (82%) was utilisable timber volume but that only 0.37 m3 (23%) was used and 0.97 m3 (59%) was left behind in the field. Merchantable logs were mainly cut into planks from which finished products - beds, chairs, doors and tables - were made. An average of 10.7 planks were cut per trunk and the local price of planks was N$45.26 at the time of the study. More income is generated from finished products compared to selling loose planks. Canopy parts were mainly cut into woodcrafts – bowls, music drums, and walking sticks. Current timber use value (N$484.73) surpasses carbon value (N$123.74). A further result of the study was that a significantly higher income could be earned for local livelihoods from Kiaat trees in the Kavango Region if trees were optimally used. Carbon trading is a noble conservation initiative, particularly when trees unsuitable for timber are considered. Use of timber trees exclusively for carbon trading is, however, not a viable option in respect of supporting local people’s livelihoods. / AFRIKAANSE OPSOMMING: Kiaatbome in Namibië word bedreig deur onvolhoubare ontginningspraktyke. Die doelwit van die studie was om die totale waarde van ‘n gemiddelde Kiaatboom, wat gekies is vir ontginning, te bepaal met die fokus op huidige houtwaarde, waarde van ‘n optimaal gebruikte boom, koolstofwaarde en alternatiewe gebruike vir Kiaatbome. Om hierdie doelwit te bereik is die volgende spesifieke sub-doelwitte gestel: (1) bepaal die totale boomvolume en optimale bruikbare houtvolume van ‘n gemiddelde Kiaatboom; (2) bepaal die hoeveelheid koolstof wat in die bogrondse dele van ‘n gemiddelde Kiaatboom gestoor word en bereken die monitêrewaarde daarvan; (3) bepaal die houtgebruiksvlakke en houtvermorsing van Kiaatbome; en (4) identifiseer alternatiewe gebruike om die vermorsing van Kiaatbome te verminder. Vorige studies oor Kiaat in Namibië en elders het gefokus op groei, ontwikkeling en sosio-ekonomiese aspekte van Kiaatbome. ‘n Kombinasie van ‘n sosio-ekonomiese opname en boomvolume en biomassa bepalings is gebruik vir die insameling van data. Die opname het ‘n Kiaat produkbepaling en gesig-tot-gesig persoonlike onderhoude met sleutel informante in en om Rundu behels. Boomkappers met permitte om kiaatbome te ontgin is gevra om 40 Kiaatbome te ontgin en data is versamel van elke boom voor en na ontginning. Die data het ingesluit: lae-stam deursnee, deursnee op borshoogte (DBH), bo-stam deursnee, stamlengte, stomphoogte, herwinde bruikbare stomplengte, bo- en onder- deursnee en lengtes van takke wat 10 cm of groter deursnee het. All kroondele 10 cm en kleiner in deursnee is geweeg en ‘n steekproef versamel wat oondroog gemaak is by 105ºC totdat konstante gewig bereik is. Die volume van verskillende boomdele is bereken en in kombinasie met houtdigtheid gebruik om biomassa te bereken. Dit is bereken dat ‘n tipiese geoeste Kiaatboom ‘n bogrondse droë volume van 1.63 m³ het, waarvan 1.34 m³ (82%) bruikbare houtvolume is. Net 0.37 m³ (23%) van die bruikbare houtvolume is egter gebruik en 0.97 m³ (59%) is agtergelaat in die veld. Bruikbare stompe is meestal opgesaag in planke waarvan finale produkte soos beddens, stoele, deure en tafels gemaak is. ‘n Gemiddeld van 10.7 planke is verkry per stomp en die plaaslike prys van planke was N$45.26 gedurende die studie tydperk. Meer inkomste is verkry van finale produkte as van die verkoop van los planke. Kroondele is meestal opgesaag in houtkunswerke soos bakke, musiekdromme en kieries. Die huidige houtwaarde van N$484.73 is meer as die koolstof waarde (N$123.74) van die bome. ‘n Belangrike resultaat van die studie is dat ‘n beduidende groter inkomste gegenereer kan word vir plaaslike lewensbestaan van Kiaatbome in die Kavangostreek as bome optimaal benut word. Koolstofhandel is ‘n edele bewaringskonsep, veral as bome ongeskik vir houtgebruik is soos in die geval van krom bome en jonger bome. Die eksklusiewe gebruik van houtbome vir koolstofhandel is nie ‘n lewensvatbare opsie om plaaslike mense se lewensbestaan te ondersteun nie.

L'objectif est de mieux connaître les bois, surtout denses et tropicaux, utilisés dans les instruments, et de proposer une aide pour la diversification en lien avec des problèmes d'approvisionnement durable. Le travail adopte deux approches complémentaires : caractérisation de la diversité des bois utilisés ou utilisables en facture instrumentale (espèces, propriétés vibratoires) ; étude des déterminants microstructuraux et chimiques (extractibles) des propriétés importantes. Une base de données « espèces ligneuses - usages en facture » est dessinée et a commencé à être implémentée par des informations de factures traditionnelles extra-Européennes. Les propriétés vibratoires élémentaires (module d'élasticité spécifique et coefficient d'amortissement dans la plage de fréquences 200-600Hz) en direction axiale, la teneur en eau à l'équilibre (à 20°C et 65% HR) et les paramètres de couleur CIELab et CIELCh sont déterminées sur 1400 éprouvettes de petites dimensions couvrant 60 espèces et 70 types de bois, dont 70% de feuillus tropicaux. Une moitié est fournie par des facteurs d'instruments, l'autre est présélectionnée sur des critères liant propriétés mécaniques, chimiques et physiques. Les relations entre propriétés sont analysées et les essences classées en groupes de similitude par analyses multivariables. Les extractibles du bois de coeur sont responsables de très faibles amortissements et teneurs en eau sur la majorité des bois tropicaux étudiés. Des modèles prédictifs simples sont proposés qui expliquent sur les essences étudiées de 85 à 90% de la variabilité observée des coefficients d'amortissement. Les relations entre propriétés physico-mécaniques et angle des microfibrilles sur des bois normaux et de compression de 3 résineux sont globalement cohérentes avec la littérature mais les bois de compression ont –à module spécifique donné- de plus faibles amortissements que les bois normaux. Les bois de coeur de deux espèces de Papilionaceae (Pterocarpus soyauxii Taub. ‘Padouk' et P. erinaceus Harms. ‘Vèn') sont comparés à l'état natif puis extraits par différents solvants. Les extraits du Padouk sont -à quantités données- plus efficaces que ceux du Vèn pour diminuer l'amortissement et inversement pour la teneur en eau. Des hypothèses sont émises sur les mécanismes possibles.