Boerewors is a South-African fresh sausage, made from beef and pork and flavoured with salt, pepper and various spices, especially coriander. It may contain a maximum of 450 mg/kg SO2 as preservative. Until recently, the use of SO2 has had GRAS (Generally Regarded as Safe) status. Investigations have indicated certain asthmatic individuals were placed at risk by relatively small amounts of sulphites. The increased demand for minimally processed, extended shelf-life foods have renewed interest in exploitation of natural antimicrobials for food preservation uses. The aim of this study was to evaluate the efficacy of Citrox as a natural preservative in Boerewors. Citrox comprises of a range of phyto-alexins derived from the pith and rind of green Bergamont oranges and fruit acids. Seven Boerewors models were made following a typical commercial procedure: the control containing no preservative, current dosage of SO2 in Boerewors (450 mg/kg), two dosages of Citrox on its own at 1% and 2% addition, a reduced amount of SO2 (100 mg/kg) on its own and Citrox in combination with reduced amounts of SO2 (1% Citrox + 100 mg/kg SO2 and 2% Citrox + 100 mg/kg SO2). The models were stored at 4 ºC for 6 days under retail display conditions. The models were evaluated every 48 hours for microbiological growth as expressed by total aerobic plate count (TAPC), coliform count, Staph. aureus count, yeast and mould count. The models were also evaluated every 48 hours for colour changes as expressed by the colour a* value (redness), colour b* value (yellowness) and colour L* value (lightness). The models were evaluated after 6 days, and again after 100 days storage at -18 ºC, for lipid oxidation as expressed by TBARS (thiobarbituric acid reactive substance). The models were also evaluated organoleptically by a sensory panel. It was established that all the treatments had significantly lower counts than the control over the 6 day storage period on TAPC. There was no significant difference in the counts of 450 mg/kg SO2, 2% Citrox, 100 mg/kg SO2 + 1% Citrox and 100 mg/kg SO2 + 2% Citrox. The 450 mg/kg SO2 and 100 mg/kg SO2 + 2% Citrox had significantly lower coliform counts than the control. Against yeasts and moulds, 100 mg/kg SO2 + 2% Citrox had significantly lower counts than the control and 450 mg/kg SO2. Citrox had a negative effect, on its own and in combination with 100 mg/kg SO2 on the colour of the Boerewors. The colour a* values were significantly lower than those for the control and 450 mg/kg SO2. There was very little effect on the colour L* value, most values stayed relatively stable over the 6 days, the 2% Citrox and 100 mg/kg SO2 + 2% Citrox showed the highest values. For all the models, there were a slight decrease in the colour b* value. At the end of the 6 days, all models had similar values. Over the 6-day fresh display period there was no significant difference in the TBARS values for all the models. After 100 days storage at -18 ºC, 450 mg/kg SO2 had significantly lower values than the control and the rest of the models. The control had the same values as the rest of the models, which led to the conclusion that although the Citrox had no anti-oxidant capabilities, it also did not increase lipid oxidation. The sensory panel found that the models containing 2% Citrox had a slight sour flavour (can be explained by the fruit acids in Citrox in combination with the vinegar added to the Boerewors formulation), however the average scores for these models were still found to be âliked slightlyâ to âliked moderatelyâ.

Developments in the biosynthesis of nanoparticles have increased significantly during the last few years as a result of the growing interest in the unique properties displayed by nanoparticles. These particles are extremely small in size and have a large surface to volume ratio, giving them unique physical and chemical properties at this scale that differs considerably from when they are used in larger form. These exceptional properties are used in a wide variety of applications, ensuing nanotechnology to become a multidisciplinary field. Research into application structure types are extended daily and as a result, the next few years will be crucial as applications for nanomaterials in the industry are most likely to be increased. Gold nanoparticles is receiving more and more attention because of its wide variety of uses in optical, electronic, magnetic, catalytic, and biomedical applications, but even more due to them being the most stable of all the metal nanoparticles. Several methods are used to produce these metal nanoparticles, but are mostly making use of toxic chemicals in the synthesis protocol, which are harmful to the environment and human health. To overcome this problem, researchers are making use of more âgreenerâ alternatives through the use of biological systems and microorganisms in nanoscience and nanotechnology. These microorganisms have unique potential in producing nanoparticles that are environmentally friendly and display different shapes, sizes and distributions. Among the different microorganisms used, bacteria have received the most attention in the nanoparticle production process, but have not been as successful as chemical synthesis to produce monodisperse noble metal nanoparticles. In this study, successful gold reduction and nanoparticle formation with different shapes, sizes and distribution was obtained; however, these particles were not monodisperse. This was achieved with a thermostable protein of ± 70 kDa that was identified as an ABC transporter, peptide-binding protein and which was purified from Thermus scotoductus SA-01; an extremophile and thermophilic bacterium that was isolated from groundwater samples from Mponeng (a deep South African gold mine in the Witwatersrand Supergroup operated by AngloGold Ashanti) at a depth of 3.2 km with ambient rock temperature of 60ºC. The protein was expressed in Escherichia coli and Thermus thermophilus HB27, a mesophilic and a thermophilic expression host respectively. It was found that the expression host might have an influence on the way the protein is folded and therefore influence nanoparticle formation. Expression studies was also done on the protein that either included or excluded Histidine-Tags and a leader peptide, but it was found that neither the His-Tags nor the leader peptide had any influence on the nanoparticles produced. Gold reduction and nanoparticle formation was obtained through reduction of a surface exposed disulphide bond in the ABC transporter, peptide-binding protein, using sodium dithionite as electron donor and reducing agent. In general it was found that nanoparticle formation was dependant on environmental parameters but control of this process was not complete. Chemical reduction did influence the nanoparticle formation process in some instances, but overall it could be seen that the presence of the protein played a significant role in slowing down the reaction rate, yielding a level of control over the nanoparticles produced and ensuring a more environmentally friendly, biological process for the production of gold nanoparticles.

As the initiative for establishing a yeast culture collection began in the early 1980âs in the department of Microbial, Biochemical and Food Biotechnology, research pertaining to the identification of isolates became the main focus. Yeasts such as Candida shehatae and Pichia stipitis claimed potential applications in the fermentation industry and received the most research attention. This research area and others reflected the potential of the culture collection as one of the sources of microbial diversity. As a result, this granted this culture collection a Microbial Resources Centre by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1996. Isolation, preservation, identification and determination of taxanomic affinities of yeasts are some of the important aspects of this culture collection in addition to others such as bioprospecting and elucidation of biotechnological applications of strains. As a general practice, these isolates must be identified reliably and rapidly using techniques such as polymerase chain reaction (PCR) and sequencing of the ribosomal DNA. Polymerase chain reaction (PCR) and sequenceing of the ribosomal DNA was mainly used in this study to identify isolates present in the UNESCO-MIRCEN Biotechnological Yeast Culture Collection. Ribosomal DNA was amplified and sequenced, followed by analysis of sequence data that was searched against available sequences on National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). In the case of new species, verification of novelty was performed by sequencing the internal transcribed spacers and doing phylogenetic analysis based on multigenic approach. New species were assigned to their phylogenetic groups and described using standardized traditional techniques. It was apparent from this study that using molecular identification methods, the number of identified ascomycetes and basidiomycetes as well as yeast-like taxa, with possible applications in the industrial, clinical, pharmaceutical, environmental and agricultural settings can be rapidly identified in great numbers. In this study, three basidiomycete strains representing new species in the genus Cryptococcus, with potential applications in cyanide bioremediation, were identified and described. These strains represent a new species which form part of a small group of yeasts (including Cryptococcus humicolus strain) with the ability to utilize inorganic cyanide as sole carbon and nitrogen source. Some of the applications and importance of strains representing known ascomycetes, basidiomycetes and yeast-like taxa are also highlighted here. Not only was the identification of isolates achieved in this study, but also full description of new yeasts present in the UNESCO-MIRCEN Biotechnological Yeast Culture Collection with possible applications in bioremediation. However, the applications of species such as Trichosporon africanensis sp. nov. will be elucidated elsewhere.

The involvement of histone acetylation in facilitating gene expression is well-established, particularly in the case of histones H3 and H4. It was previously shown in Saccharomyces cerevisiae that gene expression was significantly down-regulated and chromatin more condensed in stationary phase compared to exponential phase. We were therefore interested in establishing the acetylation state of histone H3 and H4 in stationary and in exponential phase, since the regulation of this modification could contribute to transcriptional shut-down and chromatin compaction during semi-quiescence. We made use of nano-spray tandem mass spectrometry to perform a precursor ion scan to detect an m/z 126 immonium ion, diagnostic of an N -acetylated lysine residue that allowed unambiguous identification of acetylated as opposed to tri-methylated lysine. The fragmentation spectra of peptides thus identified were searched with Mascot against the Swiss-Prot database, and the y-ion and bion fragmentation series subsequently analyzed for mass shifts compatible with acetylated lysine residues. We found that K9, K14 and K36 of histone H3 and K12 and K16 of histone H4 were acetylated in exponential phase (bulk histones), but could not detect these modifications in histones isolated from stationary phase cells. The corresponding unacetylated peptides were, however, observed. This result was confirmed by Western analysis (work not presented here). H4K16 acetylation was previously shown to disrupt formation of condensed chromatin in vitro.

Several aspects related to cereal fermentations were reviewed in the literature section of this study. These aspects included among others, the history of indigenous cereal fermentation, factors that affect cereal fermentation, potential microbiological hazards of cereal fermentation, recent advances in related industry, and the future of fermented foods. A wide variety of recipes exists across the African continent and the beers are known by many local names. In particular this study focussed on mahewu and umqombothi, both made from a combination of maize and sorghum, fermented beverages consumed in South Africa. Improved process technologies such as the use of starter cultures can lead to improved product characteristics and consequently better health attributes for the consumer of these indigenously fermented products. During the fermentation processes for umqombothi and mahewu, yeasts, lactic acid bacteria, moulds and enterobacteriaceae were present at the start of the process but as fermentation progressed yeasts and lactic acid bacteria were the dominant microorganisms. This was over a 48 h, and 3 day, fermentation period for the umqombothi and mahewu respectively. Home-, township-, and laboratorymade samples of umqobothi were compared while for mahewu, the comparison was between the home- and laboratory-made samples. Results from different production sites were not significantly different although there were instances that called for improved hygiene as contaminants were found in some samples. Yeasts isolated from umqombothi were identified and these included; Candida ethanolica, C. haemuloni, C. sorbophila, Dekkera anomala, Dekkera bruxellensis, Saccharomycopsis capsularis and Saccharomyces cerevisiae. The yeasts isolated from mahewu were identified and the predominant strains were Candida haemuloni, Candida sorbophila, Debaryomyces hansenii, Saccharomyces capsularis and Saccharomyces cerevisiae. Confirmation of the yeast identity was done using sequence analysis of the D1/D2 domain using primer pairs NL-1(5â-GCATATCAATAAGCGGAGGAAAAG) and NL-4(5â- GGTCCGTGTTTCAAGACGG). Scanning electron microscopy was performed on the interior surface of a pot used for indigenous cereal fermentation. The images obtained confirmed the presence of biofilm on the surface and the microorganisms present in this biofilm were predominantly yeasts and bacteria. The observed proximity of yeasts to the bacterial cells lent further support to the suggestion of a symbiotic relationship existing between these microorganisms in indigenous cereal fermentations. Biofilms are not homogenous in composition but are complex matrices composed of microcolonies interspersed with channels allowing the movement of fluids and nutrients. It therefore follows that a combination of different techniques that are available may be required to give the most accurate picture of the true biofilm structure and organisation. Indigenous cereal fermented products are an integral part of the diet of many African households. Several advantages do arise from the fermentation of cereals and improvement of this process will not only lead to better health attributes but also the production of fermented beverages with guaranteed and consistent quality. This augurs well for the producers of fermented products as more consumers become aware of the health properties of fermented products and this trend is only likely to improve in the future.

Cytochrome P450 monooxygenases are a superfamily of heme-containing enzymes that are found in all domains of life. P450s catalyse diverse reactions, many of which are difficult reactions to accomplish, even with the use of chemical catalysts. One such reaction is the terminal hydroxylation of alkanes, the first step in alkane degradation. The CYP153 family, found in alkane-utilising bacteria, is one of only two P450 families that can catalyse this reaction. One of the long-term goals of our groupâs research is the directed evolution of terminal alkane hydroxylases, using preferably a self-sufficient terminal alkane hydroxylase as the starting point. There are, however, no naturally self-sufficient CYP153s. Therefore, the first aim of this study was to create a self-sufficient CYP153 by fusing a CYP153 heme domain to the reductase (PFOR) domain of a self-sufficient P450. The gene encoding the heme domain of CYP153A6 from Mycobacterium sp. HXN-1500 was ligated to the DNA encoding the PFOR reductase domain of CYP116B3 from Rhodococcus ruber DSM 44319. The fusion gene was expressed in E. coli using a pET28a plasmid. The resulting protein was misfolded and expressed mainly in the insoluble fraction in the form of inclusion bodies. Factors possibly responsible for this were investigated including the expression conditions, the effect of an N-terminal His-tag on protein folding, the effect of the linker region sequence on protein folding, and the possibility of rapid expression resulting in protein misfolding, but with all of these experiments only low levels of P420s were observed in the soluble fraction and no P450 forms were detected. A whole-cell octane bioconversion experiment conducted using the expressed fusion revealed the presence of P450 forms of the protein, but no 1-octanol was produced, indicating that octane possibly facilitated the correct folding of the CYP153A6 heme domain but that the heme domain and the PFOR reductase domain were unable to form a functional complex. This theory does, however, require further research. In this study, CYP153A6 and its redox partners, ferredoxin reductase and ferredoxin were expressed in E. coli using the pET28b plasmid. Expression of CYP153A6 in E. coli using this plasmid has not previously been reported in literature. Whole-cell octane bioconversions conducted using the expressed CYP153A6 resulted in the production of 42 mM of 1-octanol after 24 hours, with the P450 concentration increasing during this time, a trend which was also observed with the fusion. The second aim of this study was to apply cassette PCR to the fusion to generate diverse selfsufficient terminal alkane hydroxylases, which would provide the genetic diversity required for directed evolution. Degenerate primers designed according to conserved N- and C-terminal regions of CYP153A amino acid sequences were used to amplify internal CYP153A gene fragments from environmental DNA extracted from enrichments of soil sampled at a dieselcontaminated site in the Eastern Cape. Three different sequences were identified, one of them being CYP153A6, which was excluded from the rest of the study. The two remaining sequences and two sequences originating from another project using environmental DNA from samples from the Beatrix Goldmine in the Free State were linked to the 5â- and 3â-ends of the CYP153A6 gene, generating full-length chimeric CYP153A genes. Because of the fact that the expression of the fusion was unsuccessful, the functionality of these chimeric genes was tested using the above-mentioned functional CYP153A6 operon. Expression was observed in the insoluble fraction in the form of inclusion bodies, with the proteins being misfolded. A whole-cell octane bioconversion did not result in P450 forms of the proteins and no 1-octanol was produced, indicating that these chimeras were non-functional.

Avibacterium paragallinarum is an avian pathogen and has the ability to cause vast economical losses. This bacterium forms part of the Pasteurellaceae family and factors contributing to pathogenicity, immunogenicity and serotyping are not clearly understood. One of the main questions that were addressed in this study was the identification of genetic tools are that is responsible for the NAD+- independence ability of this organism. NAD+ recycling genes were implicated for this bacterium and Av. paragallinarum seem to follow the recycling pathway as set out for the Pasteurellaceae family. Still the question regarding NAD+- independence remains unanswered as no complete pathway could be implicated for this trait. Furthermore, no plasmid(s) could be isolated that conferred this trait and no complete NAD+ synthesis pathway could be implicated. Only two genes were identified to form part of a NAD+-independent pathway which indicated that Av. paragallinarum may use genetic tools for NAD+-independence as set out for bacteria in general and not as the rest of the Pasteurellaceae family members. Plasmid isolation studies revealed only the plasmid p250 identical to the established plasmid p250 for Av. paragallinarum. Literature reports on two other native plasmids namely pYMH5 and pA14, however, these two plasmids could not be detected in any of the strains used in this study during plasmid screens. This study confirms and illustrates the integration of plasmid p250 within the genome of Av. paragallinarum by different serovars. In order to study this bacterium on a genomic level a whole genome sequencing project was launched. This project experienced vast amount of difficulties regarding the assembly of a complete genome for Av. paragallinarum. This bacterium contains numerous repeated regions within its genome which, with current sequencing technology, prevent the genome assembly into a single chromosome. A complete assembled genome can only be achieved when longer read lengths are available in high-throughput sequencing technologies and will thus enable clarification regarding the repeated regions. A pseudo-assembled molecule was sent to the JCVI for genome annotation. Annotated data revealed that Av. paragallinarum contains a high degree of complexity regarding its cell envelope which may shed light on pathogenicity and immunogenicity problems endured. This bacterium contains numerous mobile and extrachromosomal elements which contribute to the inability to close the genome of Av. paragallinarum. Nine site-specific integrases and 10 transposases were identified. These tools could allow for a high degree of genetic diversity within the Av. paragallinarum specie. Alongside these tools two putative prophages was identified for Av. paragallinarum. One prophage resembles the Mu-like prophages and was termed ФAvpmuC-2M, the other resembles the HP2-like prophages and was termed ФAvpC-2M-HP2.

The usual strategy to prepare gold nanoparticles involves the reduction of a gold salt in solution by various reducing agents in the presence of a stabilizer. These particles are mostly spherical with poor monodispersity. An alternative means is to use biological material to mediate particle synthesis. Microorganisms such as fungi have demonstrated the ability to produce nanoparticles of different shapes and sizes extending beyond the scope of chemical means, and the microbial interaction with metals also supply eco-friendly methods for nanoparticle production. It has been hypothesized that the proteins involved in nanoparticle synthesis require a co-factor such as NADH / NADPH, as previous studies have indicated that NADH- and NADPH-dependent enzymes are important factors in the biosynthesis of metal nanoparticles. Thermus scotoductus SA-01, a thermophilic bacterium, isolated from an AngloGold Ashanti mine near Carletonville, Republic of South Africa, was used for purification of a gold(III) reducing and nanoparticle synthesizing protein. This bacterium has the ability to produce gold nanoparticles, and more than one pathway can be followed to produce these particles. A protein was purified to homogeneity by using a combination of several liquid chromatography resins. The N-terminal sequence was obtained by using automated Edman degradation. The protein purified is not a classical oxido-reductase and was identified as an ABC transporter peptide-binding protein (~70kDa). This discovery shows that gold nanoparticles can be produced by proteins other than oxidoreductases. The interaction of the protein extracted and purified from Thermus scotoductus SA-01, as well as the recombinant proteins, with liquid gold under varying physico-chemical conditions have been studied using TEM, EDS, and by measuring the plasmon resonance band, to illustrate the effect on particle morphology and to elucidate the protein mechanism. The size and the shape of particles could, to an extent, be manipulated by controlling the environmental parameters. The purified protein as well as the recombinant proteins was only able to produce nanoparticles in the presence of sodium dithionite and it is thus hypothesized that the donation of electrons via the disulphide bridge in the protein is involved in the reduction of the gold ions. Even though the recombinant proteins had the ability toproduce nanoparticles they were not as efficient as the native protein, but when the optimum parameters for the recombinant proteins are established they could be used in the upscale production of gold nanoparticles or gold nanosheets.

Avian pathogenic Escherichia coli (APEC), the causative agent of colibacillosis belong to the family enterobacteriaceae. The disease is manifested as localised or systemic infections which include peritonitis, airsacculitis, omphalitis, swollen head syndrome and colisepticaemia in poultry. Colibacillosis results in increased mortality, condemnations of carcasses at slaughter, reduced feed conversion and production due to morbidity and increased cost of treatment. The standard method for the control of colibacillosis has been the use of antibiotics either as a treatment or as prophylaxis through the addition of antibiotics into the animal feed at sub-minimal levels. The efficacy of antibiotics has drastically reduced over the years due to the emergence and increased prevalence of antibiotic resistance. The use of some antibiotics and antibiotic growth promoters such as fluoroquinolones has been banned and further bans are still impending. Therefore, colibacillosis can potentially cripple the poultry industry nationally and worldwide, if traditional treatment options are ineffective. There is a great demand for potential alternatives to the use of antibiotics and lytic bacteriophages offer attractive advantages over antibiotics in this regard. This study focused on the isolation and characterisation of lytic bacteriophages with the aim of determining their potential to control E. coli infections, in poultry. Nine bacteriophages were successfully isolated from sewage samples and five from chicken faecal matter. The lytic patterns of the phages against E. coli K12 and E. coli strains isolated from diseased poultry (presumed to be pathogenic) were determined. Among the phages isolated from sewage samples, 31-5, E13/2, E13/5 and BS4 lysed four or more of the E. coli strains. The widest host strain range was exhibited by E13/2 which infected 8 of the 11 strains. Thus, this isolate may hold the greatest potential for therapy. In contrast, isolates from chicken faecal matter had a very narrow host strain range, lysing a maximum of two E. coli strains including the original host. An interesting observation was made in that the laboratory strain; E. coli K12 was resistant to lysis by four out of the five isolates (from chicken faecal matter). This is an important factor to consider in any potential form of treatment where only the pathogenic strains are targeted while the normal microbiota should remain unaffected. The varied lytic patterns observed for most of the isolates further demonstrate the importance of employing phage cocktails rather than single preparations to treat or prevent colibacillosis. Additionally, some of the isolates may prove useful in phage typing due to their high discriminatory nature in lysis. Although much has been reported on APEC-specific coliphages isolated from sewage, this is one of a few studies where they have been successfully isolated from chicken faecal matter. Examination of morphological characteristics by transmission electron microscopy revealed the presence of a majority of tailed phages which are members of the Myoviridae and Siphoviridae families. For some viruses definite conclusions could not be made concerning their identity and they were therefore only tentatively placed into certain families. Molecular analyses included polymerase chain reaction (PCR) using primers specific for the g23 sequence of T4-type phages and the DNA polymerase of T7-like podophages. Although the identity of every phage isolate could not be inferred, the relatedness between isolates SK4 and SK5 was established using the PCR technique of random amplified polymorphic DNA (RAPD). Phylogenetic investigations revealed that 31-5 and SK5 were closely related followed by E13/5 and SK4. In conclusion, this study demonstrated that some of the isolated phages have the potential to prevent, eliminate or reduce APEC in poultry. Further research is however, necessary to fully characterise the phage isolates and perform efficacy tests in vivo.

Mycoplasma gallisepticum (MG) is an economically important pathogen of poultry worldwide, causing chronic respiratory disease in both chickens and turkeys. Little research has been done to characterize the MG field strains present in southern Africa. Field evidence however, suggested breaks in the vaccinations against MG, despite the proper cold chain and correct administration. Molecular methods were used to screen various poultry farms in South Africa and Zimbabwe for MG. Isolates were further characterized by gene-targeted sequencing (GTS). Portions of the cytadhesin pvpA, gapA, mgc2 genes and the uncharacterized surface lipoprotein gene designated MGA_0319 were sequenced and analysed. Three MG strains were identified in this study: a Ts-11-like strain; a strain showing closest percentage identity to the atypical MG RV-2 strain found in Israel, however with the lack of a large deletion within the pvpA region; and lastly an isolate from Zimbabwe, likely to be a novel MG strain. The latter contained a unique, large, in-frame nucleotide insertion in the mgc2 gene. Antigenically-significant variation (determined in silico) within the membrane surface proteins of this isolate was found compared to the MG Rlow strain used as an inactive vaccine on the poultry farm. It is thus postulated that by MG altering its antigenic profile, it allows effective avoidance of immune recognition and antibodies produced as a result of vaccination with inactivated and possibly live MG vaccines. Further research is however needed to substantiate this claim.