(R)-phenylacetylcarbinol or R-PAC is a chiral precursor for the synthesis of pharmaceuticals ephedrine and pseudoephedrine. PAC is produced through biotransformation of pyruvate and benzaldehyde catalyzed by pyruvate decarboxylase (PDC) enzyme. The present research project aims at characterizing a two-phase aqueous/organic process for enzymatic PAC production. In a comparative study of several selected yeast PDCs, the highest PAC formation was achieved in systems with relatively high benzaldehyde concentrations when using C. utilis PDC. C. tropicalis PDC was associated with the lowest by-product acetoin formation although it also produced lower PAC concentrations. C. utilis PDC was therefore selected as the biocatalyst for the development of the two-phase PAC production. From an enzyme stability study it was established that PDC deactivation rates in the twophase aqueous/octanol-benzaldehyde system were affected by: (1) soluble octanol and benzaldehyde in the aqueous phase, (2) agitation rate, (3) aqueous/organic interfacial area, and (4) initial enzyme concentration. PDC deactivation was less severe in the slowly stirred phase-separated system (low interfacial area) compared to the rapidly stirred emulsion system (high interfacial area), however the latter system was presumably associated with a faster rate of organic-aqueous benzaldehyde transfer. To find a balance between maintaining enzyme stability while enhancing PAC productivity, a two-phase system was designed to reduce the interfacial contact by decreasing the organic to aqueous phase volume ratio. Lowering the ratio from 1:1 to 0.43:1 resulted in increased overall PAC production at 4??C and 20??C (2.5 M MOPS, partially purified PDC) with a higher concentration at the higher temperature. The PAC was highly concentrated in the organic phase with 212 g/L at 0.43:1 in comparison to 111 g/L at 1:1 ratio at 20??C. The potential of further two-phase process simplification was evaluated by reducing the expensive MOPS concentration to 20 mM (pH controlled at 7.0) and employment of whole cell PDC. It was found that 20??C was the optimum temperature for PAC production in such a system, however under these conditions lowering the phase ratio resulted in decreased overall PAC production. Two-phase PAC production was relatively low in 20 mM MOPS compared to biotransformations in 2.5 M MOPS. Addition of 2.5 M dipropylene glycol (DPG) into the aqueous phase with 20 mM MOPS at 0.25:1 ratio and 20??C improved the production with organic phase containing 95 g/L PAC. Although the productivity was lower, the system may have the benefit of a reduction in production cost.

Agriculture, industry and medicine are being altered by new biological technologies. Today's students are the citizens who will make decisions about associated ethical issues. They need to have the knowledge that will enable them to make informed choices. Hence biotechnology has an important place in science education. The aims of the research were to: 1/describe the state of biotechnology teaching in NSW; 2/determine whether teachers in NSW do not teach biotechnology because they do not have the necessary knowledge and experience; 3/identify other reasons why NSW teachers choose not to teach biotechnology; 4/describe problems encountered in teaching biotechnology in NSW; 5/suggest ways in which the problems encountered in the teaching of biotechnology can be overcome. Quantitative and qualitative methods were used in a complementary way to investigate these aims. In a sample of teachers surveyed, many reported that they chose not to teach biotechnology because they did not have adequate knowledge and experience. Other obstacles were identified. These were: 1/ the difficulty of the subject matter; 2/ the lack of practical work; 3/ lack of a program for biotechnology in junior science. The results of this trial suggested that a biotechnology unit should be developed in collaboration with the teacher and that time needs to be made available for school based program development. / Master of Education (Hons)

(R)-phenylacetylcarbinol or R-PAC is a chiral precursor for the synthesis of pharmaceuticals ephedrine and pseudoephedrine. PAC is produced through biotransformation of pyruvate and benzaldehyde catalyzed by pyruvate decarboxylase (PDC) enzyme. The present research project aims at characterizing a two-phase aqueous/organic process for enzymatic PAC production. In a comparative study of several selected yeast PDCs, the highest PAC formation was achieved in systems with relatively high benzaldehyde concentrations when using C. utilis PDC. C. tropicalis PDC was associated with the lowest by-product acetoin formation although it also produced lower PAC concentrations. C. utilis PDC was therefore selected as the biocatalyst for the development of the two-phase PAC production. From an enzyme stability study it was established that PDC deactivation rates in the twophase aqueous/octanol-benzaldehyde system were affected by: (1) soluble octanol and benzaldehyde in the aqueous phase, (2) agitation rate, (3) aqueous/organic interfacial area, and (4) initial enzyme concentration. PDC deactivation was less severe in the slowly stirred phase-separated system (low interfacial area) compared to the rapidly stirred emulsion system (high interfacial area), however the latter system was presumably associated with a faster rate of organic-aqueous benzaldehyde transfer. To find a balance between maintaining enzyme stability while enhancing PAC productivity, a two-phase system was designed to reduce the interfacial contact by decreasing the organic to aqueous phase volume ratio. Lowering the ratio from 1:1 to 0.43:1 resulted in increased overall PAC production at 4??C and 20??C (2.5 M MOPS, partially purified PDC) with a higher concentration at the higher temperature. The PAC was highly concentrated in the organic phase with 212 g/L at 0.43:1 in comparison to 111 g/L at 1:1 ratio at 20??C. The potential of further two-phase process simplification was evaluated by reducing the expensive MOPS concentration to 20 mM (pH controlled at 7.0) and employment of whole cell PDC. It was found that 20??C was the optimum temperature for PAC production in such a system, however under these conditions lowering the phase ratio resulted in decreased overall PAC production. Two-phase PAC production was relatively low in 20 mM MOPS compared to biotransformations in 2.5 M MOPS. Addition of 2.5 M dipropylene glycol (DPG) into the aqueous phase with 20 mM MOPS at 0.25:1 ratio and 20??C improved the production with organic phase containing 95 g/L PAC. Although the productivity was lower, the system may have the benefit of a reduction in production cost.

Thesis (M.Ed.) (Hons.) -- University of Western Sydney, Nepean, 1999. / Submitted for the degree of Master of Education (Hons.), University of Western Sydney, Nepean. Bibliography : p. 120-126.

Thesis (Ph. D.)--Open University. BLDSC no. DX186045.

Thesis (Ph.D.)--York University, 2003. Graduate Programme in Environmental Studies. / Typescript. Includes bibliographical references (leaves 415-441). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99137

Thesis (MSc (Botany and Zoology. Plant Biotechnology))--University of Stellenbosch, 2005. / Sugarcane (Saccharum spp) is an important crop worldwide and is cultivated for the high level of sucrose in its mature internodes. Because of the exhaustion of the genetic potential in the commercial sugarcane germplasm conventional breeding has not lately been able to enhance sucrose content. Currently there is a concerted effort to improve culm sucrose content by genetic engineering which will require appropriate transgenes and promoters. One of the major constraints to genetic engineering of sugarcane is the lack of stable promoters required to drive tissue- or organ-specific expression of transgenes. Tissue and developmental stage specific promoters allow targeting of transgene activity and in doing so reduce the impact on non-target tissues. These promoters could also be advantageous to manipulate certain aspects of sucrose metabolism specifically in mature culm tissue. In addition, no promoters are currently freely available to the South African Sugar Industry for use in their transgenic program. The primary goal of this project was therefore to isolate a mature tissue-specific promoter for use in transgenic sugarcane plants. The approach followed was firstly, to identify an endogenous gene expressed in the desired pattern, and then to isolate the corresponding promoter from the sugarcane genome. cDNA macroarrays were initially used to identify differentially expressed sequences. The tissue specificity of potential clones was confirmed using RNA blot analysis. Two clones (c23-a and c22-a) were isolated and confirmed to be mature culm specific. Clone c22-a (putative dirigent-like protein) was selected for promoter isolation based on its culm tissue specific expression pattern and its proximity to the 5’ end of the gene. Furthermore, to confirm the activity of this promoter in the storage parenchyma cells, the exact cellular localisation of the transcript in the mature tissue was determined through in situ hybridisation. In situ hybridisation results confirmed the presence of the transcript in the parenchyma cells of mature culm tissue only. Moreover, the transcript is present in high concentrations in the parenchyma tissues surrounding the vascular bundles and parenchyma cells of the vascular complex. The selected dirigent-like gene was sequenced to allow the design of primers that could be used for the isolation of the corresponding promoter region using a long-range inverse PCR (LR-iPCR) method. Using these we have successfully isolated two highly homologous promoter regions of the dirigent like gene of respectively 1151 and 985 base pairs. In silico analyses confirmed the presence of various transcription motifs, including a TATA-box. However, experimental verification is needed to fully assess the functionality of these promoter regions. Verifying the activity of the isolated promoters through transient expression analysis proved to be problematic because of their highly mature culm specificity. Both constructs are therefore being used to obtain stable transformants in which promoter activity can be evaluated in mature internodal tissues.

The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.

M.B.A. / The debate over plant biotechnology and genetic engineering (GE) is surrounded with controversy. On the one side of the debate, phrases such as `Frankenfood' and `terminator seed' have been used to describe food and seed resulting from plant biotechnology. On the other hand, Agricultural Scientists see biotechnology and genetic engineering as a solution to keep feeding and clothing the increasing world population with static or reducing world resources. Many farmers in developing countries eke out a living based on the production techniques that are becoming increasingly unaffordable because of increasing inputs cost and are no longer producing enough output to provide adequate access to food. Plant biotechnology holds the potential for increasing the productivity of agriculture in developing countries. New crop varieties are developed which are resistant to insects and are tolerant to certain non-selective herbicides. All these plant biotechnology developments are said to help reduce the cost of inputs, protects yields and reduce environmental contamination with toxic insect sprays. For many commercial farmers, cotton production is the only possibility they have to produce a cash crop but spraying to control insect pests is required several times during the season resulting in high input costs. An alternative to spraying is to introduce a built-in defense into the plant itself to combat insect damage. The introduction of the insecticidal gene from the bacterium Bacillus thuringiensis (Bt) into the cotton plant trough biotechnology, has secured a built-in defense against the most common insect family in cotton namely the lepidopteran caterpillar. Cotton engineered with such genes was introduced into commercial production for the first time in 1996 with over 1.8 million acres planted with transgenic cotton in the US. Following early trials, Bt-cotton has since the 1998/99 growing season been commercialized in South Africa. Since the introduction of genetically engineered (GE) crops, US farmers have rapidly adopted most of them. Analyses by USDA's Economic Research Services (ERS) and others indicate economic benefits to many farmers adopting first-generation GE crops. This research study was carried out to determine to what extend the South African cotton growers embraced this kind of technology through usage thereof and if they benefited as much as other cotton farmers world-wide. The specific research objectives for this study were as follows: An evaluation of the adoption rates and benefits derived from plant biotechnology on a worldwide base through literature. An evaluation of the acceptance and penetration of Bt-cotton amongst the South African commercial cotton growers. To determine the benefits of Bt-cotton to the South African commercial cotton growers. To determine to what extend the South African cotton growers benefited economically through the use of the Bt-cotton trait. To identify segmental differences in the adoption of the Bt-cotton trait amongst commercial cotton growers in South Africa. The main findings of this research indicate that almost three quarters of the cotton hectares surveyed were planted with the Bt-cotton trait and that almost ninety percent of cotton growers surveyed, adopted the Bt-cotton trait in the 2001/2002 season. Comparing the benefits derived from Bt-cotton in South Africa to those in other countries, it can be concluded that the South African commercial cotton growers had equal results. Most of the cotton growers in South Africa experienced yield increases with a substantial reduction in the use of insecticides. This resulted in higher gross margins from Bt-cotton compared to the non-Bt cotton or commercial cotton varieties. The South African commercial cotton grower has benefited agronomically, economically and environmentally through the adoption of the Bt-cotton trait. Future introductions of plant biotechnology traits such as herbicide tolerance will further enhance the production potential of cotton.

Benzoylformate decarboxylase (BFD) from Pseudomonas putida catalyzed the formation of 2-hydroxy-1-phenylpropanone (2-HPP), a 2-hydroxy ketone, from the kinetic resolution of rac-benzoin in the presence of acetaldehyde. The formation rate of 2-HPP via kinetic resolution of benzoin was 700-fold lower compared to the formation via direct carboligation of benzaldehyde and acetaldehyde. Further investigations revealed that BFD not only accepts (R)-benzoin but also 2-HPP as the substrate. A typical Michaelis–Menten type kinetics was observed starting from enantiopure (S)- or (R)-2-HPP. The formation of racemic 2-HPP while using benzoin as the donor in the presence of acetaldehyde and the racemization of (R/S)-2-HPP were detected. The equilibrium constant determined, showed favoured conditions towards the product side i.e. (R)-benzoin and 2-HPP. In the end, an extended reaction mechanism was proposed by supplementing the already known mechanism with the C–C bond cleavage activity of BFD towards 2-hydroxy ketones. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.