Determination of aflatoxins in peanut (Arachis hypogaea L.) collected from Kinshasa, Democratic Republic of Congo and Pretoria, South Africa : a comparative study

This study assessed the mycological and aflatoxin contamination of peanuts collected from Kinshasa, DRC and Pretoria, South Africa. Forty peanut samples were collected randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (B1, B2, G1 and G2) using standard methods. The results indicated that 95% and 100% of peanut samples collected from Kinshasa and Pretoria, respectively were contaminated with aflatoxigenic fungi with Kinshasa’s samples being the most contaminated (up to 49, 000 CFU/g). Seventy percent (70 %) of Kinshasa-samples and 35% of Pretoria-samples exceeded the maximum allowable limit of aflatoxin B1 set by JECFA (5 ppb). Statistical evidence showed a significant positive correlation between mycoflora and aflatoxin level for Kinshasa-samples (r = 0.4743, p < 0.005) while Pretoria-samples showed no correlation. The study reveals that high level of contamination in Kinshasa-samples could be due to the tropical nature of the climate and poor storage conditions as compared to Pretoria which is sub-tropical and sanitary regulations are enforced.Life and Consumer SciencesM. Sc. (Life Sciences

Assessing the resistance and bioremediation ability of selected bacterial and protozoan species to heavy metals in metal-rich industrial wastewater

<p>Abstract</p> <p>Background</p> <p>Heavy-metals exert considerable stress on the environment worldwide. This study assessed the resistance to and bioremediation of heavy-metals by selected protozoan and bacterial species in highly polluted industrial-wastewater. Specific variables (i.e. chemical oxygen demand, pH, dissolved oxygen) and the growth/die-off-rates of test organisms were measured using standard methods. Heavy-metal removals were determined in biomass and supernatant by the Inductively Couple Plasma Optical Emission Spectrometer. A parallel experiment was performed with dead microbial cells to assess the biosorption ability of test isolates.</p> <p>Results</p> <p>The results revealed that the industrial-wastewater samples were highly polluted with heavy-metal concentrations exceeding by far the maximum limits (in mg/l) of 0.05-Co, 0.2-Ni, 0.1-Mn, 0.1-V, 0.01-Pb, 0.01-Cu, 0.1-Zn and 0.005-Cd, prescribed by the UN-FAO. Industrial-wastewater had no major effects on <it>Pseudomonas putida</it>, <it>Bacillus licheniformis</it> and <it>Peranema</it> sp. (growth rates up to 1.81, 1.45 and 1.43 d^-1, respectively) compared to other test isolates. This was also revealed with significant COD increases (p < 0.05) in culture media inoculated with living bacterial isolates (over 100%) compared to protozoan isolates (up to 24% increase). Living <it>Pseudomonas putida</it> demonstrated the highest removal rates of heavy metals (Co-71%, Ni-51%, Mn-45%, V-83%, Pb-96%, Ti-100% and Cu-49%) followed by <it>Bacillus licheniformis</it> (Al-23% and Zn-53%) and <it>Peranema</it> sp. (Cd-42%). None of the dead cells were able to remove more than 25% of the heavy metals. Bacterial isolates contained the genes <it>copC</it>, <it>chrB</it>, <it>cnrA3</it> and <it>nccA</it> encoding the resistance to Cu, Cr, Co-Ni and Cd-Ni-Co, respectively. Protozoan isolates contained only the genes encoding Cu and Cr resistance (<it>copC</it> and <it>chrB</it> genes). <it>Peranema</it> sp. was the only protozoan isolate which had an additional resistant gene <it>cnrA3</it> encoding Co-Ni resistance.</p> <p>Conclusion</p> <p>Significant differences (p <���0.05) observed between dead and living microbial cells for metal-removal and the presence of certain metal-resistant genes indicated that the selected microbial isolates used both passive (biosorptive) and active (bioaccumulation) mechanisms to remove heavy metals from industrial wastewater. This study advocates the use of <it>Peranema</it> sp. as a potential candidate for the bioremediation of heavy-metals in wastewater treatment, in addition to <it>Pseudomonas putida</it> and <it>Bacillus licheniformis</it>.</p

Evaluation of the Digestibility of Attached and Suspended Growth Sludge in an Aerobic Digester for a Small Community

The aerobic sludge digestion process for waste sludge generated from suspended biomass (i.e., activated sludge process, ASP) and attached biomass (i.e., moving bed bioreactor, MBBR and modified packed bed biofilm, PBBR) reactors in a residential complex were analyzed. The rate of digestion with respect to different sludge characteristics generated through these various treatment processes were examined; the results revealed that waste sludge from ASP took 16 days to achieve complete digestion while MBBR and PBBR took nine and seven days, respectively. The most important factors influencing the sludge digestion such as sludge volume index (SVI), mixed liquor suspended solid (MLSS), and mixed liquor volatile suspended solid (MLVSS) were examined. The ASP which had the highest initial MLSS and MLVS took a longer time for digestion. Aerobic sludge digestion in all the treatment reactors was studied under laboratory scale conditions in batch experimentation to evaluate sludge characteristics and the rate of digestion as well as through a continuous bench scale pilot system to optimize the process parameters. Removal efficiencies of volatile solids (VS) 90.71% in ASP, 84.27% in MBBR and 84.07% in PBBR in aerobic digestion during batch mode were also observed. The study revealed that the aerobic sludge digestion process utilized in curbing sludge is not feasible application for a small community due to very long digestion times and a large amount of space although Packed Bed Biofilm (PBBR) used the lowest time (seven days) compared to the other systems

Microbial diversity of Emalahleni mine water in South Africa and tolerance ability of the predominant organism to vanadium and nickel.

The present study aims firstly at determining the microbial diversity of mine-water collected in Emalahleni, South Africa and secondly isolating and characterizing the most dominant bacterial species found in the mine water in terms of its resistance to both V(5+) and Ni(2+) in a modified wastewater liquid media. The results revealed a microbial diversity of 17 orders, 27 families and 33 genera were found in the mine-water samples with Marinobacteria (47.02%) and Anabaena (17.66%) being the most abundant genera. Considering their abundance in the mine-water samples, a species of the Marinobacter genera was isolated, identified, and characterised for metal tolerance and removal ability. The MWI-1 isolate (Marinobacter sp. MWI-1 [AB793286]) was found to be closely related to Marinobacter goseongensis at 97% of similarity. The isolate was exposed to various concentrations of Ni(2+) and V(5+) in wastewater liquid media and its tolerance to metals was also assessed. The MWI-1 isolate could tolerate V(5+) and Ni(2+) separately at concentrations (in terms of MIC) up to 13.41 ± 0.56 mM and 5.39 ± 0.5 mM at pH 7, whereas at pH 3, the tolerance limit decrease to 11.45 ± 0.57 mM and 2.67 ± 0.1 mM, respectively. The removal of V(5+) and Ni(2+) in liquid media was noted to gradually decrease with a gradual increase of the test metals. A significant difference (p<0.05) between V(5+) and Ni(2+) removal was noted. Marinobacter sp. MWI-1 achieved the maximum permissible limit of 0.1 mg-V(5+)/L prescribed by UN-FAO at 100 mg/L, while at 200 mg/L only V(5+) was removed at approximately 95% and Ni(2+) at 47%. This study suggests that mine-water indigenous microorganisms are the best solution for the remediation of polluted mine water

Agarose gel electrophoresis of PCR products of total genomic DNAs with primers targeting gene nccA (Lane: 4), van2 (lane: 3), smtAB (lane: 2) and cnrB2 (lane: 1).

<p>Lanes: M: DNA ladder (Marker) and B: Negative (No template DNA).</p

Summary of pyrosequencing data from mine water samples.

<p>Summary of pyrosequencing data from mine water samples.</p

MWI-1 isolate tolerance limits (MIC and 24 h LC₅₀) to V⁵⁺ and Ni²⁺, and removal ability in the modified liquid media (n = 5).

<p>MWI-1 isolate tolerance limits (MIC and 24 h LC₅₀) to V⁵⁺ and Ni²⁺, and removal ability in the modified liquid media (n = 5).</p

Composition of the bacterial orders, family and genera detected in the mine water with sequences of the variable region V1–3 of the 16S rRNA genes.

<p>Composition of the bacterial orders, family and genera detected in the mine water with sequences of the variable region V1–3 of the 16S rRNA genes.</p

Profile of mine water samples collected from the vanadium mine, South Africa (n = 3).

<p>Profile of mine water samples collected from the vanadium mine, South Africa (n = 3).</p