Applied Sciences

This paper reports the presence of new antibiotic-producing organisms in the relatively under investigated 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 mg/ml and 0.0025 mg/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.

"Awo freshwater stream in Akure, Ondo State, which has no history of pollution, was examined to determine the effect of 5% pollution on dissolved oxygen, biochemical oxygen demand, and the microbial population. Results showed that there were significant effect on each of the above parameters. The toxic effect of crude oil on heterotrophic bacteria ranged from 50% to 93%. The relative abundance of hydrocarbon-utilizing heterotrophic bacteria increased from 0.007% before the effect to 0.020% after the pollution. These results imply that the microbial community composition of the stream is altered by crude oil pollution.
KEYWORDS: Crude oil, pollution, freshwater, Nigeria, bacteria."

Cassava is currently being investigated for biogas production in South Africa as it offers multiple benefits such as high yields of starch and total dry matter. The chemical constituents of the cassava biomass were determined using standard methods. Using a local laboratory batch fermenter, anaerobic digestion was carried out in a 25 L capacity digester maintained at 36±0.5o C. Pre-treatment of the cassava biomass with spoilage fungi, Aspergillus niger and Penicillium species yielded large amounts of fermentable sugars for digestion. Cassava slurry was made and mixed with Zebra droppings (2:1 v/v) and loaded into the digester of 20 L working volume. Analysis results showed an increase in most nutrients after pretreatment except for starch which decreased from 76% to 60% as a result of its hydrolysis to fermentable sugars by the spoilage fungi. Theoretical biogas yields were between 0.71 and 0.75 nm3 per kg VS destroyed while the total biogas yields of between 250 and 300 m3 per kg VS fed into the digester was obtained after 20 days residence time. Cassava is not yet a staple food in some BRICS countries like South Africa and the peels and other by-products of its processing are equally suitable for energy production. The use of cassava will be an alternative feedstock strategy for several rural biogas projects running with cow dungs inside South Africa. In addition, opportunities exist for decentralized, cheaper and socially advantageous bioenergy production from cassava considering that fuel and electricity needs are not satisfied in many rural areas. Finally, the incorporation of cassava anaerobic digestion facility at different scales will deliver additional benefits like the incorporation of nutrients and residual carbon into the land as fertilizer.

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. 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 and a more holistic and complementary view of food and biomass energy production. In conclusion, it recommend considering cassava and its biomass as the next energy crop for biogas production in Africa and especially South Africa.

Keywords
Cassava; Biomass; Biogas; Bioenergy; Anaerobic digestion; South Africa

In this study, the concentration levels of the probable carcinogenic PAH fractions, benzo[a]pyrene (BaP) and benzo[k]fluoranthrene (BkF) in fillets of some processed fish species were investigated. Fish species comprising Merluccius poli (hake), Tyrsites atun (snoek), Seriola lalandi (yellow-tail) and Brama brama (angel fish) were bought in fish shops at Gordon's Bay, Western Cape, South Africa. The fish were gutted, filleted and prepared for edibility by frying, grilling and boiling. Polycyclic aromatic hydrocarbons were extracted from each homogenized fish sample, cleaned-up using solid phase extraction (SPE), and analysed for the PAH fractions, BaP and BkF using a Gas Chromatograph coupled with a Flame Ionization Detector (GC-FID). The sum of the two PAHs (∑2PAH) i.e., BaP and BkF ranged between 0.56 and 1.46 µg/kg, in all boiled, grilled and fried fish species. The fried fish extracts showed significantly higher (p < 0.05) abundance of ∑2PAH, than grilled and boiled fish....

Organotin compounds result from the addition of organic moieties to inorganic tin.Thus, one or more tin-carbon bonds exist in each organotin molecule. The organo-tin compounds are ubiquitous in the environment. Organotin compounds have many uses, including those as fungicides and stabilizers in plastics, among others in industry. The widespread use of organotins as antifouling agents in boat paints has resulted in pollution of freshwater and marine ecosystems. The presence of organotin compounds in freshwater and marine ecosystems is now understood to be a threat, because of the amounts found in water and the toxicity of some organotin compounds to aquatic organisms, and perhaps to humans as well. Organotin com-pounds are regarded by many to be global pollutants of a stature similar to biphenyl,mercury, and the polychlorinated dibenzodioxins. This stature results from the high toxicity, persistence, bioaccumulation, and endocrine disruptive features of even very low levels of select...

Phytotoxic effects of Pb as Pb(NO 3) 2 on tomato (Lycopersicon esculentum) planted on contaminated soil was assessed in terms of growth, yield and Vitamin C content at various concentrations (300, 600 and 1800 ppm). The residual Pb was also determined in the soil used for plant cultivation and in the experimental plant tissues. Results showed that plant performance significantly reduced with increasing concentrations of Pb contamination. Residual Pb was detected in the tomato roots and shoots, but non in the fruits. Results also showed that Vitamin C content of the tomato was not affected by various concentrations of the Pb contaminants. Pb contamination has adverse effects on tomato production but not on Vitamin C content.

Maize cob was used as an adsorbent in order to evaluate its potential for the removal of lead from aqueous solutions and effluents from battery and paint industries with Dowex (synthetic resin) as control. Experimental data were analyzed in terms of Freundlich isotherm model. Equilibrium was attained at 2 h and adsorption rate constants for maize cob and dowex were 7.26 x 10 -2 and 7.58 x 10 -2 min -1 , respectively. Equilibrium pH value was 6; shaking at 150 rpm enhanced adsorption with maximum adsorption by both adsorbents in battery and paint effluents. Optimal weight at equilibrium for the adsorbents in Pb 2+ solution was 16 mg/L of solution. Pb 2+ removal by maize cob from battery effluent was 99.99% while it was 47.38% for Dowex. Corresponding values from paint effluents were 66.16 and 27.83%. The study concludes that maize cob has great potentials to remove Pb 2+ from industrial effluents.