Browsing by Author "Coetzee, G."

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    Effect of rooibos and honeybush tea extracts against Botrytis cinerea
    (SASEV, 2008-02) Coetzee, G.; Marx, I. J.; Pengilly, M.; Bushula, V. S.; Joubert, E.; Bloom, M.
    Green tea extracts from the indigenous South African rooibos (Aspalathus linearis) and honeybush (Cyclopia species) plants were evaluated as potential antifungal agents against the plant pathogen Botrytis cinerea. When applied at 10 mg/ml, the tea extracts stimulated biomass production in B. cinerea by more than 3-fold after 24 hrs. This induction could not be linked directly to the presence of selected micro- and macronutrients or antioxidants in the extracts, suggesting a complex set of yet unidentified factors that may act synergistically to enhance cell growth. However, when applied at 100 mg/ml, the A. linearis and C. genistoides extracts reduced spore germination of B. cinerea by 33.3% and 16.7%, respectively. This suggests that the tea extracts contain active compounds that should be further investigated for their potential as natural anti-fungal agents.
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    Epidemiology of post-neonatal bacterial meningitis in Cape Town children
    (Health & Medical Publishing Group, 1997) Hussey, G.; Schaaf, H. Simon; Hanslo, D.; Hitchcock, J.; Coetzee, G.; Pitout, J.; Malan, H.; Donald, P.
    Bacterial meningitis is a major cause of childhood morbidity and mortality in South Africa. However, comprehensive regional or national epidemiological data, essential for rational public health interventions, are lacking. The purpose of this 1-year prospective study, from 1 August 1991 to 31 July 1992, was to define the magnitude of the problem of childhood bacterial meningitis in Cape Town. The study group consisted of all children, aged > 1 month to < 74 years, who presented with proven bacterial meningitis at all the hospitals in the Cape Town metropolitan area. During the year 201 cases were identified: 101 (50.2%) were due to Neisseria meningitidis, 74 (36.8%) were due to Haemophilus influenzae and 26 (12.9%) were due to Streptococcus pneumoniae. The overall incidence rate (95% confidence interval) for children less than 14 years, 5 years and 1 year was 34 (30 - 40), 76 (65 - 88) and 257 (213 - 309) per 100 000 children, respectively. The rate was highest in black infants, 416 (316 - 545)/100 000. This was 2 times greater than the rate in coloured infants and about 4.5 times greater than the rate in white infants. The median age of all the children was 10 months. The ages of children with haemophilus and pneumococcal meningitis were similar, 9 and 7.5 months respectively (P = 0.43), while children with meningococcal meningitis were significantly cider (22 months) than the others (P < 0.01). The overall case fatality rate was 5%, and 12.9% of survivors had significant neurological sequelae (disability) on discharge.
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    Scalable methanol‑free production of recombinant glucuronoyl esterase in Pichia pastoris
    (BMC (part of Springer Nature), 2019) Conacher, C. G.; Garcia‑Aparicio, M. P.; Coetzee, G.; Van Zyl, W. H.; Gorgens, J. F.
    Objective: Glucuronoyl esterase (GE) is an emerging enzyme that improves fractionation of lignin-carbohydrate complexes. However, the commercial availability of GE is limited, which hinders the research of GE-based bioprocesses for its industrial application in lignocellulose biorefineries. This study evaluated a workable, cost-effective, and commercially scalable production strategy to improve the ease of GE-based research. This strategy consisted of a constitutive and methanol-free enzyme production step coupled with a two-step filtration process. The aim was to determine if this strategy can yield copious amounts of GE, by secretion into the extracellular medium with an acceptable purity that could allow its direct application. This approach was further validated for cellobiose dehydrogenase, another emerging lignocellulose degrading enzyme which is scarcely available at high cost. Results: The secreted recombinant enzymes were functionally produced in excess of levels previously reported for constitutive production (1489–2780 mg L−1), and were secreted at moderate to high percentages of the total extracellular protein (51–94%). The constant glycerol feed, implemented during fed-batch fermentation, lead to a decline in growth rate and plateaued productivity. Tangential flow ultrafiltration was used to concentrate cell-free enzyme extracts 5–6-fold, reaching enzyme activity levels (1020–202 U L−1) that could allow their direct application.