ResearchSpace :: Browsing by Author "Ndlela, Luyanda L"

Browsing by Author "Ndlela, Luyanda L"

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Antimicrobial resistance screening and profiles: A glimpse from the South African perspective
(2020-12) Genthe, Bettina; Ndlela, Luyanda L; Madlala, Tebogo
According to the Centre for Disease Dynamics Economics and Policy, South Africa represents a paradox of antibiotic management similar to other developing countries, with both overuse and underuse (resulting from lack of access) of antibiotics. In addition, wastewater reuse may contribute towards antibiotic resistance through selective pressure that increases resistance in native bacteria and on clinically relevant bacteria, increasing resistance profiles of the common pathogens. Sediments of surface water bodies and wastewater sludge provide a place where antibiotic resistance genes are transferred to other bacteria. Crop irrigation is thought to be a potential source of exposure to antibiotic-resistant bacteria through the transfer from the water or sludge into crops. The objectives of this study were to examine the antibiotic-resistance profiles of Escherishia coli from three agricultural locations in the Western Cape, South Africa. Using a classical microbiology culture approach, the resistance profiles of E. coli species isolated from river water and sediments, farm dams and their sediments and a passive algal wastewater treatment ponds and sediment used for crop irrigation were assessed for resistance to 13 commonly used antibiotics. Randomly selected E. coli isolates from the sediment and water were tested for resistance. 100% of E. coli isolates were resistant to sulphamethoxazole, highlighting its relevance in the South African context. In river water and farm dam samples, only the E. coli isolated from sediment were found to be resistant to fluoroquinolone or fluorifenicol. In the wastewater treatment ponds, the resistance profiles of E. coli isolated from sediments differed from those isolated from effluent, with 90% of the effluent isolates being resistant to ampicillin. Isolates from the sediment were less resistant (40%) to ampicillin, whereas all the isolates from the pond water and sediment samples were resistant to sulphamethoxazole. These results illustrate the importance of developing a better understanding of antibiotic resistance in agriculture and wastewater scenarios to ensure remedial measures take place where the greatest benefit can be realised especially in countries with limited financial and infrastructural resources. Moreover, the potential for passive algal treatment as an effective, feasible alternative for wastewater treatment is highlighted, with comparable resistance profiles and a reducing overall resistance in the sediment samples.
Assessing alternative supporting organic materials for the enhancement of water reuse in subsurface constructed wetlands receiving acid mine drainage
(2022-06) Oberholzer, MM; Oberholster, PJ; Ndlela, Luyanda L; Botha-Oberholtster, AM; Truter, CJ
Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated.
Atlas of industrial wastewater reuse potential in South Africa
(CSIR, 2021-03) Steyn, Maronel; Walters, Chavon R; Mathye, Salamina M; Ndlela, Luyanda L; Thwala, Melusi; Banoo, Ismail; Tancu, Yolanda; Genthe, Bettina
The South African economy largely depends on mining and other large industries. According to the National Water Resources Strategy 2 (DWA, 2013a), the mining sector, with an estimated demand of about 5% of the country’s available water, is a significant user of water. Coal and Platinum mining in particular is currently expanding into new areas with a projected increase in water demand. Many of these mines are located in water resource scarce catchments (e.g. the Lephalale and Steelpoort areas in the Limpopo province) where the availability of water can become a significant business risk. Water availability should however not be a limiting factor to growth in the country. Water resources management and development should prioritise availability of water to industry. Similarly, implementation of water conservation and water demand management (WC/WDM) measures within the mining sector is required in order to minimise this risk (DWS, 2016).
Bacteria as biological control agents of freshwater cyanobacteria: is it feasible beyond the laboratory?
(Springer, 2018-12) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, JH; Cheng, Po Hsun H
Biological control of cyanobacteria is a well-researched area with a central focus on laboratory-scale studies. Numerous reports have been made on algicidal isolates, with bacteria as a major component of the antagonists. The research in this review draws a brief summary of what is currently known in the area of freshwater cyanobacteria being inhibited by bacterial isolates. Proteobacteria, Bacteroidetes and Firmicutes are among the most commonly reported phyla of bacteria associated with or employed in this research area. However, there are limited reports of upscaling these control measures beyond the laboratory scale. Lytic control agents are the most commonly reported in the literature with subsequent cyanotoxin release. From a water quality perspective, this is not feasible. Based on the available literature, temperature, pH and nutrient changes have been explored in this short review as possible contributors to less optimal bacterial performance. Moreover, the investigation into optimising some of these parameters may lead to increased bacterial performance and, therefore, viability for upscaling this biological control. Through the compilation of current research, this review offers insight to live predator-prey cell interactions between cyanobacteria and algicidal bacteria.
Bacterial control of cyanobacteria
(2017-08) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, Johannes
With the effects of climate change, harmful algal blooms (HABs) have become a global concern, with serious implications in water scarce countries and vulnerable continents such as Africa. A need exists for low-cost, environmentally feasible treatment which can be up-scaled for managing toxic cyanobacterial blooms, especially in countries like South Africa, which is water scarce and has had reports of blooms of Cylindrospermopsis, Oscillatoria, Anabaena and Microcystis across the country.
Biological control of toxic cyanobacteri
(2017-05) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, J; Cheng, Po-Hsun
With the effects of climate change, harmful algal blooms (HABs) have become a global concern, with serious implications in water scarce countries such as South Africa. There is a specific lack of information in the African continent regarding harmful algal blooms and their impacts in over 30 countries. Biological control is a method of introducing natural enemies to control an organism and has been more successful using microorganisms.
Biological control of toxic cyanobacteria
(CSIR, 2016-04) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, J
With the effects of climate change, harmful algal blooms (HABs) have become a global concern, with serious implications in water scarce countries such as South Africa. There is a specific lack of information in the African continent regarding harmful algal blooms and their impacts in over 30 countries. Biological control is a method of introducing natural enemies to control an organism and has been more successful using microorganisms.
Bulk scale industrial effluent reuse potential in South Africa
(2021-11) Steyn, Maronel; Walters, Chavon R; Mathye, Salamina M; Thwala, Melusi; Banoo, Ismail; Ndlela, Luyanda L; Tancu, Yolanda; Genthe, Bettina
Rationale: Water scarcity, increased pollution, unprecedented population growth and climate change are collectively driving the need to reuse water with the aim to enhance water security, sustainability, and resilience. It is clear that South Africa’s already strained water resources will become even more stressed in the near future. The Department of Water and Sanitation predicted that by 2030 water demand will reach 17.7 billion m3, far more than what is available to allocate. Globally, responsible and efficient water management is fast becoming a pressing reality for domestic users, agriculture and industry alike. The challenge is therefore to capitalise on the limited water we currently have. Solution: Bulk-scale reuse of industrial water effluent can play a significant role in water security in a water scarce country, such as South Africa, as it can augment or partially substitute freshwater resources needed for domestic purposes and future development. Water reuse in South Africa is however lagging. Approach: An Atlas for potential industrial bulk scale water reuse was produced from publicly available Natsurv and WARMS data. It highlights the urgent need for water reuse to form an integral part of an integrated water management supply approach in South Africa. While South Africa has progressive legislation to support the implementation of wastewater reuse, it can also be regarded as a barrier in implementing reuse projects, as often water reuse standards and guidelines are far too stringent to allow for cost-effective reuse options to be developed and implemented. Findings: Currently, very little to no data exists regarding wastewater reuse options, treatment options and capabilities, or costs, which can be used for decision making, and much more directed research and information is needed in order to identify wastewater and industrial effluent volume availability, quality and fitness for use in South Africa. A web-based Decision Support System (DSS) tool is being developed to enable municipal and industry partners, and water quality managers to make informed decisions for possible reuse options. The tool aims to directly assist by linking industrial effluent volumes and quality to fitness for use, and linking it with specific industries in the geographical vicinity based on industry specific water quality and quantity requirements. The DSS can be particularly useful in wastewater reuse as it can provide assistance in the evaluation and selection of alternatives for a given reuse application. In addition, the tool will enable engineers and industry partners to collaborate to identify and employ treatment technologies and capabilities to link industrial effluent quality and volumes available to that of potential user requirements in a geographical area.
Bulk scale industrial effluent reuse potential in South Africa Atlas
(2021-10) Steyn, Maronel; Walters, Chavon R; Mathye, Salamina M; Thwala, Melusi; Ndlela, Luyanda L; Tancu, Yolanda; Lehutso, Raisibe F; Banoo, Ismail
Globally, responsible and efficient water management is fast becoming a pressing reality for domestic users, agriculture and industry alike. The challenge is therefore to capitalise on the limited water we currently have. Solution: Bulk-scale reuse of industrial water effluent can play a significant role in water security in a water scarce country, such as South Africa, as it can augment or partially substitute freshwater resources needed for domestic purposes and future development. Water reuse in South Africa is however lagging. Approach: An Atlas for potential industrial bulk scale water reuse was produced from publicly available Natsurv and WARMS data. It highlights the urgent need for water reuse to form an integral part of an integrated water management supply approach in South Africa.
Evaluation of the probable synergistic toxicity of selected potentiated antiretroviral and antibiotics on some aquatic biomarker organisms
(2023-11) Omotola, EO; Genthe, B; Ndlela, Luyanda L; Olatunji, OS
Environmental effects of active pharmaceutical compounds (APCs) in the environment are not well characterized, hence the need for comprehensive evaluation. This study employed three bioassays using three organisms, namely, Allium cepa, Daphnia magna, and Salmonella typhimurium, in the ecotoxicity study of lone and a mixture of selected APCs, namely, lamivudine (L), an antiretroviral, and ciprofloxacin (C) and sulfamethoxazole (S), antibiotics, at a concentration range between 10 and 100 ppb, in order to evaluate the potential of the lone and ternary mixture to exert synergistic toxicity. Study results from exposure to lone APCs showed that the L, C, and S trio individually had fatal impacts on daphnids, with mortality rates of 100, 75, and 95%, respectively, after 48 h. Sulfamethoxazole showed a mutagenic tendency, with a mutation ratio (background/sample ratio) of 2.0. Lamivudine showed a lethal impact on the root length of A. cepa (p > 0.05, p = 3.60E-3). Further microscopic examination of the A. cepa root tip revealed chromosomal aberrations on exposure to each compound. The LCS-mix ecotoxicology bioassays indicated a synergistic effect on the daphnids, probably due to potentiation. Although the LCS mix had a cytotoxic effect (evidenced by the absence of bacteria colonies) on exposed TA 98 P450 Salmonella typhimurium strain, this effect was not observed in other bacterial strains. Microscopic examination of A. cepa exposed to the LCS-mix revealed an aberration in the mitotic stage of the cell. The impact of combination of the pharmaceuticals in aqueous ecosystems was greater than when exposed to the tested individual pharmaceutical compounds. Study result showed that these compounds have tendencies to pose a higher risk to exposed living entities when in combined/potentiated forms, and this could lead to distortion of the regular functioning of the ecosystem, particularly bacterial and other microbial populations that are listed among primary producers of the aquatic food web.
Evaluation of wild herbivore faeces from South Africa as a potential source of hydrolytically active microorganisms
(Springer, 2016-02) Ndlela, Luyanda L; Schmidt, S
This study assessed faecal matter from three indigenous South African herbivores-zebra, giraffe and impala-as a potential source for hydrolytically active aerobic and facultatively anaerobic bacteria. Herbivore droppings were collected freshly in a local nature reserve in Pietermaritzburg, South Africa. Soil samples adjacent to faecal collection sites and faeces from a domestic herbivore, the Nguni cow, were included as controls. Hydrolase and dehydrogenase activity in faecal matter and soil samples were measured by the fluorescein diacetate and the triphenyltetrazolium chloride assay. Viable counts and counts for amylase, cellulase, esterase and protease producers were established using plate count agar and solid media containing cellulose, skim milk, starch and Tween 80. Zebra droppings produced the highest hydrolase and dehydrogenase activity. Faecal matter of the three indigenous herbivores generally produced higher hydrolytic activity than Nguni cow faeces and soil controls, thereby confirming that these materials are potential targets for hydrolytic enzyme mining.
Insights into the ecotoxic impact of diclofenac using Daphnia magna as a model organism
(2023-06) Omotola, EO; Genthe, Bettina; Ndlela, Luyanda L; Olatunji, SO
Residues of pharmaceutical compounds (PCs) are among the groups of contaminants of emerging concerns that have been reportedly detected in the aquatic environment. These compounds are widely distributed in diverse water bodies, thus, necessitating eco-toxicological assessment of PCs. However, data concerning the risk they pose to unintended non-target species in different ecosystems are still very scanty and scarce. This study investigated the ecotoxic effect of diclofenac, an analgesic, on freshwater aquatic ecosystem using the sensitive Daphnia magna (water flea) bioassay. The daphnid bioassay was carried out at concentrations 10 µg/L and 100 µg/L, which are the least and upper-end detection (LED & UED) values of the range of concentrations of diclofenac detected in the tested aquatic water columns, as well as reported levels in some international surveys. The 24 to 48-hr Daphnia magna test revealed a mortality rate of > 75 % and 90 % for 100 µg/L diclofenac, respectively, in freshwater-spiked samples. These results suggest that the presence of PCs in aqueous ecosystems may pose a lethal impact on aquatic fauna at the detected levels in the environment.
A laboratory based exposure of Microcystis and Oscillatoria cyanobacterial isolates to heterotrophic bacteria
(Elsevier, 2019-04) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, JH; Cheng, Po Hsun
Biological control of cyanobacteria is a viable means of controlling nuisance bloom occurrences; however the majority of studies done are against Microcystis sp., with a commonly lytic effect caused. Filamentous cyano-bacteria such as Oscillatoria are not as extensively studied in this area of biological control and are often part of Microcystis dominated blooms. This study employed heterotrophic bacterial isolates selected from bloom waters that indicated potential predatory behaviour against both filamentous and colonial cyanobacterial isolates. In comparison to a known Bacillusisolate, which is often reported among bacterial control agents, three other bacteria isolates were tested as control agents against non axenic Oscillatoria and Microcystis cyanobacterial cultures. Assessments of cyanobacterial cell responses to the bacteria were conducted through water chemistry, chlorophylla, alkaline phosphatase activity, microscopy and cyanotoxin measurements. The changes in these parameters were compared to untreated cyanobacterial cultures where no bacteria were added. The study found that at ratios of bacteria half that of Microcystis, minimal changes in chlorophylla were observed, whilst Oscillatoria showed a decreased chlorophyll a more in the presence of isolates 1 and 3w. The assessment of alkaline phosphatase activity showed decreased activity in both cyanobacterial isolates exposed to the bacteria, relative to the untreated control sample. Microscopy analysis through fluorescence indicated that the attachment of the bacteria to the surface of the cyanobacteria hampered with the fluorescence and scanning electron mi-croscopy indicated that the cells were damaged by the addition of the bacterial isolates. Cyanotoxin detection through the ELISA kit testing indicated that there was toxin reduction in samples treated with the bacterial isolates, with the highest reduction being close to 60% in the case of Microcystis sp. treated with isolate 3w. Similar reductions were noted in the filamentous cyanobacterium Oscillatoria, in the presence of isolate 1.
Optimisation of surfactant decontamination and pre-treatment of waste chicken feathers by using response surface methodology
(Elsevier, 2018-02) Tesfaye, T; Sithole, Bishop B; Ramjugernath, D; Ndlela, Luyanda L
Commercially processed, untreated chicken feathers are biologically hazardous due to the presence of blood-borne pathogens. Prior to valorisation, it is crucial that they are decontaminated to remove the microbial contamination. The present study focuses on evaluating the best technologies to decontaminate and pre-treat chicken feathers in order to make them suitable for valorisation. Waste chicken feathers were washed with three surfactants (sodium dodecyl sulphate) dimethyl dioctadecyl ammonium chloride, and polyoxyethylene (40) stearate) using statistically designed experiments. Process conditions were optimised using response surface methodology with a Box-Behnken experimental design. The data were compared with decontamination using an autoclave. Under optimised conditions, the microbial counts of the decontaminated and pre-treated chicken feathers were significantly reduced making them safe for handling and use for valorisation applications.
An overview of cyanobacterial blooms occurrences and research in Africa over the last decade
(Elsevier, 2016-12) Ndlela, Luyanda L; Oberholster, Paul J; Van Wyk, JH; Cheng, Po-Hsun
Cyanobacterial blooms are a current cause for concern globally, with vital water sources experiencing frequent and increasingly toxic blooms in the past decade. These increases are resultant of both anthropogenic and natural factors, with climate change being the central concern. Of the more affected parts of the world, Africa has been considered particularly vulnerable due to its historical predisposition and lag in social economic development. This review collectively assesses the available information on cyanobacterial blooms in Africa as well as any visible trends associated with reported occurrences over the last decade. Of the 54 countries in Africa, only 21 have notable research information in the area of cyanobacterial blooms within the last decade, although there is substantial reason to attribute these blooms as some of the major water quality threats in Africa collectively. The collected information suggests that civil wars, disease outbreaks and inadequate infrastructure are at the core of Africa’s delayed advancement. This is even more so in the area of cyanobacteria related research, with 11 out of 21 countries having recorded toxicity and physicochemical parameters related to cyanobacterial blooms. Compared to the rest of the continent, peripheral countries are at the forefront of research related to cyanobacteria, with countries such as Angola having sufficient rainfall, but poor water quality with limited information on bloom occurrences. An assessment of the reported blooms found nitrogen concentrations to be higher in the water column of more toxic blooms, validating recent global studies and indicating that phosphorous is not the only factor to be monitored in bloom mitigation. Blooms occurred at low TN: TP ratios and at temperatures above 12 °C. Nitrogen was linked to toxicity and temperature also had a positive effect on bloom occurrence and toxicity. Microcystis was the most ubiquitous of the cyanobacterial strains reported in Africa and the one most frequently toxic. Cylindrospermopsis was reported more in the dry, north and western parts of the continent countries as opposed to the rest of the continent, whilst Anabaena was more frequent on the south eastern regions. In light of the entire continent, the inadequacy in reported blooms and advances in this area of research require critical intervention and action.
Phycoremediation of industrial wastewater: Review of algae consortia
(2024-10) Walters, Chavon R; Steyn, Maronel; Ndlela, Luyanda L; Nocanda, Xolani W; Moloi, M; Oberholster, Paul
Industrialisation, population growth, and concomitant demand for fresh water have immensely impacted water quality and scarcity. In particular, wastewater generated from industries generally produces high amounts of nutrients, heavy metals, and chemicals that degrade the environment. Several algal species have been studied and utilized for their role in the treatment of various types of wastewater. Conventional wastewater treatment options are often expensive and energy-demanding, and generally ineffective at completely removing contaminants. Conversely, phycoremediation technology is an emerging green approach used to remove various types of pollutants from the environment while producing valuable compounds. Compared to conventional methods, phycoremediation presents as an eco-friendly and economically attractive alternative. This paper serves as a review of an algal-based treatment technology in wastewater remediation for industry, describing the most common microalgal consortia used for this purpose. Phycoremediation challenges and strategies to urgently accelerate steps towards achieving a clean and safe environment are presented, while examples of applications in industries are also provided.
Phytotoxicity and apoptotic impact assessment of an over-the-counter drug (paracetamol) residue using Allium cepa as a bioindicator
(2023-06) Omotola, EO; Genthe, Betty; Ndlela, Luyanda L; Olatunji, SO
Pharmaceutical compounds (PCs) present in the environment can induce adverse toxic consequences on exposed biotic features. Some PCs have been reported to exert fatal impacts on aquatic fauna. However, information on their toxic actions on plants, which are critically essential to ecosystems’ health and balance, is scarce and scanty. This study investigated the adverse phytotoxic and apoptotic impacts of a common over-the-counter drug (paracetamol) residue at environmental levels of 0.01 and 0.1 mg/L, using Allium cepa (A. cepa) as a bioindicator. The inhibition of the germination rate of A. cepa root tip was employed as indices (after a 4-day exposure) for assessing paracetamol’s phytotoxicity, while deoxyribonucleic acid (DNA) fragmentation assay was used in the apoptotic investigation of paracetamol. It was observed that 0.1 mg/L paracetamol had a phytotoxic impact on the germination rate of A. cepa root tips relative to the control (p<0.05), while there was no phytotoxic impact exerted by 0.01 mg/L paracetamol. Furthermore, microscopic examination showed irregular prophase in the onion cells. The DNA fragmentation assay revealed the induction of apoptosis by 0.1 mg/L paracetamol, while no apoptosis was induced by 0.01 mg/L paracetamol. Based on the findings from this study, paracetamol can be said to be phytotoxic and bring about DNA damage when exposed to plants at environmental levels. It is therefore recommended that policies be put in place to remediate the environment as regards the removal of paracetamol residues.
Removal of antibiotics using an Algae-Algae consortium (Chlorella protothecoides and Chlorella vulgaris)
(2023-07) Ndlela, Luyanda L; Genthe, Bettina; Schroeder, P; Cruzeiro, C
The intensive use of antibiotics (for human, veterinary, and agricultural purposes) has steadily increased over the last 30 years. Large amounts of antibiotic residues are released into aquatic systems, mostly due to inefficient wastewater treatment. Conventional wastewater treatments are not designed to remove emerging contaminants (such as antibiotics) from wastewater. Therefore, algae treatment (phycoremediation) has emerged as a promising choice for cost-effective, eco-friendly, and sustainable wastewater treatment. For this reason, we investigated the removal performance of a well-established algal consortia (Chlorella protothecoides and Chlorella vulgaris) used in passive wastewater treatment ponds (Mosselbay, South Africa). Five antibiotics (sulfamethoxazole, amoxicillin, trimethoprim, ofloxacin, and clarithromycin) were selected for their ubiquity and/or low removal efficiency in conventional wastewater treatment plants (WWTPs). For each antibiotic, two concentrations were used: one environmentally relevant (10 ppb) and another 10 times higher (100 ppb), tested in triplicate and collected at two-time points (7 and 10 days). The algae remained viable over the exposure period (which is similar to the retention time within maturation ponds) and exhibited the capacity to remove sulfamethoxazole (77.3% ± 3.0 and 46.5% ± 5.3) and ofloxacin (43.5% ± 18.9 and 55.1% ± 12.0) from samples spiked with 10 and 100 ppb, respectively. This study demonstrates the potential and innovation of algal remediation for contaminants in a developing country context, where minimal infrastructure is available.

Browsing by Author "Ndlela, Luyanda L"

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