http://hdl.handle.net/11189/5119 Sun, 16 Aug 2026 08:30:55 GMT 2026-08-16T08:30:55Z https://digitalknowledge.cput.ac.za:443/retrieve/23246/ http://hdl.handle.net/11189/5119 http://hdl.handle.net/11189/5222 Title: Antimicrobial activity of rare actinomycetes isolated from natural habitats in KwaZulu-Natal, South Africa. Authors: Okudoh, VI; Wallis, FM Abstract: This paper reports the presence of new antibiotic-producing organisms in the relatively underinvestigated region of KwaZulu-Natal, South Africa. Using a modified agar-streak method and selective isolation media during the primary screening phase, eighty isolates showing antimicrobial activity were isolated from soil samples of various habitats in the KwaZulu-Natal Midlands. The use of selective isolation media, with antibiotic incorporation and/or heat pretreatment, enhanced the isolation of certain rare actinomycete colonies. The number of culturable antibiotic-producing microorganisms constituted about 3% (on average) of the total microbial population in the different samples studied. The highest percentage of antimicrobially active isolates came from a forest soil site whereas the lowest percentage was present in a riparian soil. One of the isolates, N8, tentatively identified as an Intrasporangium species, was isolated from barnyard soil at a poultry farm. It produced at least one broad-spectrum antibiotic active against both Gram-positive and Gram-negative bacteria and fungi and also inhibited the growth of all seven test organisms, especially Pseudomonas fluorescens and Xanthomonas campestris pv campestris at minimum inhibitory concentrations (MIC) of 0.0625 µg/ml and 0.0025 µg/ml, respectively. To our knowledge, members of this actinomycete genus have not been associated previously with antibiotic production. These data confirm that KwaZulu-Natal soils harbour rare actinomycetes that inhibit the growth of Pseudomonas fluorescens and Xanthomonas campestris pv campestris, representatives of two genera which are notoriously difficult to contain in the field. Such antibiotic producers should become more commercially important if the current trend towards the use of biocontrol agents rather than chemical treatments of plant diseases persists Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/11189/5222 2007-01-01T00:00:00Z http://hdl.handle.net/11189/4454 Title: The potential of cassava biomass and applicable technologies for sustainable biogas production in South Africa: A review Authors: Okudoh, Vincent Ifeanyi; Trois, Cristina; Workneh, Tilahun; Schmidt, Stefan Abstract: Bioenergy production from agricultural crop biomass or residues is gaining interest due to the escalating cost of fossil fuels and the need to mitigate global warming caused by increasing GHG emissions. Of all the different feed stocks used for bioenergy production in Africa, cassava biomass potentially offers multiple benefits for producing biofuels such as biogas. This critical review on cassava intends to highlight the bioenergy (biogas) potential of the crop in Africa. Initially, the basic agricultural properties of cassava will be reviewed. Cassava contains large amounts of fermentable sugars. Its starch content ranges from 20 to 35% based on fresh and at about 80.6% based on dry weight with 38.6% total dry matter. It has the highest yield of carbohydrates per hectare with the exception of sugarcane and sugar beet. It thrives well in all ecological zones with one of the best water-footprints especially on relatively low fertility soils, in drought conditions and requires low agrochemical input. High yielding and disease resistant cassava varieties have been developed for both food and non-food applications with China adopting the crop to meet its 2020 biofuel target. Based on the available literature, various pretreatment techniques including mechanical, chemical, thermal, ultrasonic and wet explosion strategies were considered. The advantages and disadvantages of each technology as well as adoptable technologies for cassava biogas production and its optimization in Africa and especially South Africa will be critically discussed. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/11189/4454 2014-01-01T00:00:00Z http://hdl.handle.net/11189/3530 Title: Enhanced Recovery and Identification of a Tryptamine-Related Antibiotic produced by Intrasporangium Authors: Okudoh, Vincent Ifeanyi; Wallis, Frederick M. Abstract: Purpose: To isolate and identify an antibiotic produced by a soil bacterium, Intrasporangium strain N8, with antibacterial activity against both Gram-positive and Gram-negative bacteria. Methods: Fermentation followed by extraction using a three-solvent system (petroleum ether, acetone and ethyl acetate) and pH precipitation, successfully separated the antibiotic complex from the culture broth. Purification was carried out using flash column chromatography (FCC), thin-layer chromatography (TLC) and reverse phase high performance liquid chromatography (HPLC). The identities of the molecules were elucidated by gas chromatography-mass spectrometry (GC-MS) analysis. Results: Three main components of the antibiotic were isolated and identified as 4-methyl-3-penten-2-one, 4-hydroxy-4-methyl-2-pentanone and N-acetyltryptamine. Bioassay results showed activity against both mammalian and plant pathogenic bacteria including Pseudomonas fluorescens, Xanthomonas campestris pv campestris, Escherichia coli and Serratia marcescens. Pseudomonas fluorescens (MIC = 0.0625 μg/ml) and Xanthomonas campestris pv campestris (MIC = 0.0026 μg/ml) represent the two plant pathogenic genera that are notoriously difficult to contain in the field. Conclusions: Since the antibiotic isolated during this study showed activity against both mammalian and plant pathogenic bacteria, it is hoped that this work will encourage further investigation in this field. This antibiotic could become very useful as an agricultural bacteriocide against some resistant plant pathogens. Mon, 01 Oct 2012 00:00:00 GMT http://hdl.handle.net/11189/3530 2012-10-01T00:00:00Z http://hdl.handle.net/11189/3349 Title: The potential of cassava biomass and applicable technologies for sustainable biogas production in South Africa: A review Authors: Okudoh, Vincent Ifeanyi; Trois, Cristina; Workneh, Tilahun; Schmidt, Stefan Abstract: Bioenergy production from agricultural crop biomass or residues is gaining interest due to the escalating cost of fossil fuels and the need to mitigate global warming caused by increasing GHG emissions. Of all the different feed stocks used for bioenergy production in Africa, cassava biomass potentially offers multiple benefits for producing biofuels such as biogas. However, its potential for food and non-food applications has so far been grossly underestimated by farmers and energy operators in Africa. This critical review on cassava intends to highlight the bioenergy potential of the crop especially for biogas production in Africa. Initially, the basic agricultural properties of cassava will be reviewed. Cassava contains large amounts of fermentable sugars. Its starch content is in the range of 20-35% based on fresh and at about 80.6% based on dry weight with a total dry matter content of 38.6%. It has the highest yield of carbohydrates per hectare with the exception of sugarcane and sugar beet. It thrives well in all ecological zones with one of the best water-footprints especially on soils of relatively low fertility, in drought conditions and requires low agrochemical input. High yielding and disease resistant cassava varieties have been developed for both food and nonfood applications with China adopting the crop to meet its 2020 biofuel target. Based on the available literature, various pretreatment techniques including mechanical, chemical, thermal, ultrasonic and wet explosion strategies were considered. In addition, the use of co-digestion and stimulation of microbial activity will be highlighted. The advantages and disadvantages of each technology as well as adoptable technologies for cassava biogas production and its optimization in Africa and in particular in South Africa will be critically discussed. This review highlights the highly politicized food vs energy debate as the most relevant bottleneck for using “potential” food (like cassava and other energy crops) for energy production. It suggests a paradigm shift on both sides of the debate and a more holistic view of food and biomass energy production which can be very complementary rather than exclusive. In conclusion, this review recommend considering cassava and its biomass as the next energy crop for biogas production in Africa and especially South Africa while providing guidance to future researchers and government policy makers. Description: Okudoh, V; Trois, C; Workneh, T; Schmidt, S; (2014). “The potential of cassava biomass and applicable technologies for sustainable biogas production in South Africa: A review”. - The definitive, peer-reviewed and edited version of this article is published in Renewable and Sustainable Energy Reviews: 39(2014)1035–1052, DOI: 10.1016/j.rser.2014.07.142 Sun, 30 Nov 2014 00:00:00 GMT http://hdl.handle.net/11189/3349 2014-11-30T00:00:00Z