School of Biological and Physical Sciences

Allelopathic potential of Tithonia diversifolia (Hemsl.) A.Gray and Lantana camara L. Leafy materials on growth, photosynthetic performance and yield of SB 19 and SB 97 soybean varieties

Wed, 01 Jan 2025 00:00:00 GMT

Allelopathic potential of Tithonia diversifolia (Hemsl.) A.Gray and Lantana camara L. Leafy materials on growth, photosynthetic performance and yield of SB 19 and SB 97 soybean varieties KHAVERE, Emily Kavuludi Soybean is a legume which is widely grown in western Kenya for its edible seed but their yields are reduced by the effect of low soil fertility. The use of forest tree species and weeds as green manure has exacerbated soil fertility issues, potentially due to the allelopathic chemicals present in these organic materials. In Western Kenya, farmers are being encouraged to use shrubs as green manure such as Tithonia diversifolia and Lantana camara which have shown to improve soil fertility by 24% to 54%. Soybean varieties, SB97 and SB19 are known to be good yielders, whereas the two plants are being used as organic manure to increase nutrients in the soil for better crop growth and productivity, they are however also known to have allelopathic effects on some crops. Information available on their allelopathic potential on photosynthetic pigment, chlorophyll fluorescence and growth of soybean is not exhaustive. The main objective of this study was to investigate the allelopathic effects of fresh leaf aqueous extracts and fresh leaf material of T. diversifolia and L. camara on germination of seeds, growth, photosynthetic performance and yield of SB97 and SB19 soybean varieties. The specific objectives were to determine allelopathic effects of aqueous extract of L. camara and T. diversifolia on germination of SB97 and SB19 soybean varieties, to determine the allelopathic effects of fresh leaf segments of L. camara and T. diversifolia on growth and yield of SB97 and SB19 soybean varieties and to determine allelopathic effects of fresh leaf segments of L. camara and T. diversifolia on chlorophyll pigments and chlorophyll fluorescence of SB97 and SB19 soybean varieties. The experiments were carried out in the laboratory and greenhouse at Maseno University. In the lab, different concentrations of aqueous extracts, (25%, 50%, 75%, and 100%) and the control- tap water was used. Germination experiment was set in petri dishes and growth, yield and physiological parameters was carried out in the green house. Fresh leaf material of T. diversifolia and L. camara of 4g, 8g, 12g and 16g was added to soil in pots. The control only composed soil. This was replicated four times and laid out in Completely Randomized Design (CRD). Data on germination count were recorded daily, while growth and physiological parameters were recorded weekly. Data were subjected to analysis of variance (ANOVA) using SAS 9.1 to establish significant differences among treatments, varieties and plant materials. The treatment means were separated and compared using the Least Significance Differences (LSD) at P = 0.05. The results revealed that leaf extracts from Lantana camara and Tithonia diversifolia reduced the germination of both soybean varieties. These extracts contained bioactive compounds that inhibited germination, root and shoot growth and yield of Soybean varieties SB 19 and SB 97. Lantana camara exhibited stronger allelopathic activity than Tithonia diversifolia. On growth parameters, including shoot height, leaf number, leaf area, fresh and dry weights, and yield, the presence of allelochemicals in the biomass was suggested to have hindered growth by disrupting enzyme activities and nutrient uptake. Chlorophyll fluorescence and chlorophyll concentration analysis revealed that both leaf biomass materials impacted negatively on photosynthetic activity of the soy bean varieties. Allelochemicals in the fresh leaf segments of these plants decreased maximum photochemical efficiency and quantum efficiency, potentially reducing photosynthetic activity. Farmers are therefore advised not to incorporate Lantana camara and Tithonia diversifolia leafy biomass in farms where soy bean varieties SB 19 and SB 97 are growing. Master's Thesis

Characterization of maize rhizospheric microflora and evaluation of their antagonistic potential against Ustilago maydis

Wed, 01 Jan 2025 00:00:00 GMT

Characterization of maize rhizospheric microflora and evaluation of their antagonistic potential against Ustilago maydis OSENDI, Rosemary Opwondi Maize common smut, attributed to Ustilago maydis, poses a significant risk to maize farming across Kenya. Despite the known potential of rhizospheric microorganisms in biological disease control, limited information exists on their population, characterization, and efficacy against U. maydis in local maize cultivars. Additionally, data on their in vivo effect on disease incidence and severity remain largely unexplored. This study was designed to determine the bacterial and fungal populations within the maize rhizosphere, characterize them using morphological and biochemical characters, and evaluate the impact of selected microbial isolates on disease incidence and severity of common smut in maize. The study was conducted under field, laboratory, and greenhouse conditions at Maseno University. Two maize varieties, DK 8033 and Duma 43 were sown at the university farm in a completely randomized block design. Rhizospheric soil samples were collected at 30 and 60 days after sowing with a soil auger and trowel, into aseptic containers, then conveyed to the botany lab for analysis. Triplicate soil samples were processed via serial dilution followed by plating to recover colonies, which were counted and characterized morphologically and biochemically. Dual culture assays were conducted in vitro to evaluate antagonism against U. maydis. Four promising antagonists: Serratia spp., Bacillus spp., Aspergillus spp., and unidentified fungal isolate MF14, were selected for in vivo greenhouse trials in three replicates, with ten treatments arranged in a completely randomized layout. Treatments included maize cultivars with microbial isolates alongside pathogen inoculation. Controls comprised maize inoculated with the pathogen and distilled water. Comparisons among treatment means used Fisher’s Least Significant Difference, at P ≤ 0.05. There were 25 bacterial and 26 fungal isolates obtained and characterized. Results revealed significantly higher bacterial counts (134.69 × 10⁸ cfu /g) than fungal counts (34.58 × 10⁸ cfu /g), both peaking at 60 days. There were 15 bacterial genera, including Bacillus, Pseudomonas, and Serratia, and six fungal genera (Penicillium, Trichoderma, Fusarium, Alternaria, Aspergillus, Curvularia). In vitro, MF14 isolate showed the highest inhibition zone (22.00 mm), followed by Serratia spp. (19.00 mm), Bacillus spp. (16.00 mm), and Aspergillus spp. (15.00 mm). Greenhouse trials showed that the unidentified fungal isolate MF14 reduced disease incidence and severity to 49.3%, outperforming other treatments. Serratia spp and Aspergillus spp. showed moderate suppression, while Bacillus spp. showed minimal but superior protection to control. This study highlights indigenous rhizospheric microorganisms with potent antagonistic activity, particularly MF14 isolate. Findings provide foundational data for developing microbial-based biocontrol strategies, offering eco-friendly biocontrol options for maize farmers in Kenya upon further research. Master's Thesis

Effect of waterlogging on growth and development of selected green gram (Vigna radiata L.) varieties

Wed, 01 Jan 2025 00:00:00 GMT

Effect of waterlogging on growth and development of selected green gram (Vigna radiata L.) varieties OCHAR, Samson Onyango In Kenya, green gram is mostly grown in arid and semi-arid areas under rainfed agricultural systems for both subsistence and commercial purposes. KAT 00301, KAT 00308, KAT 00309, KS20, N22 and N26 are grown in Kenya. However, the commonly grown varieties are KAT 00301 (dengu tosha), KAT 00308 (dengu biashara) and KAT 00309 (dengu karembo). Climate change has caused unpredictable rainfall patterns followed by floods which has led to waterlogging, which limits green gram production by affecting morpho-physiological and biochemical parameters hence food insecurity. There is need to fully understand morpho-physiological, biochemical and yield response of selected green gram varieties to waterlogging in order to identify waterlogging-tolerant varieties. The general objective of the study was to determine the effect of waterlogging on growth and development of selected green gram varieties. The specific objectives were to determine the effect of waterlogging on morphological, physiological, chlorophyll content and yield components of selected green gram varieties. The research was carried out under greenhouse set-up at the University Botanic Garden, Maseno. Ten-litre pots were arranged in a completely randomized design and filled with solarised soil obtained from the University Botanic Garden. Five seeds of KAT 00301, KAT 00308 and KAT 00309 were planted in the pots. Each pot was watered with 500 ml of water daily after and before the waterlogging treatment period. This continued throughout the study period. At 14 days after sowing (DAS), seedlings in each pot were thinned to three. Waterlogging treatments were induced at 21 DAS by dipping the 10-litre pots in larger 20-litre pots and maintaining standing water at 3 cm above the soil level for 3 days, 6 days and 9 days. The control treatment was watering each pot daily with 500 ml water throughout the study period. Each treatment had three replications. Collection of data began on 37 DAS and continued after every seven days throughout the study period. Morphological parameters data, i.e., the number of leaves were counted and fresh weight was determined using digital weighing balance. Data on physiological parameters; photosynthesis rate, stomatal conductance and transpiration rate were measured using LI-680 portable photosynthesis systems. Total chlorophyll content was determined using the Arnon method. Number of days to 50% flowering was counted and dry weight of 100 grains was determined using digital weighing balance. The data was subjected to analysis of variance using Statistical Analysis System (SAS) and separation of means done using LSD test at 5% level. Waterlogging significantly (P≤0.05) decreased the number of leaves, fresh weight, stomatal conductance, photosynthesis rate, transpiration rate, chlorophyll content and weight of 100 grains but significantly increased the days to 50 % flowering of the selected green gram varieties. The fresh weight, photosynthesis rate, chlorophyll content and weight of 100 grains were significantly lower in KAT 00308 as compared to KAT 00301 and KAT 00309. The number of days to 50% flowering in KAT 00308 was significantly more as compared to KAT 00301 and KAT 00309. KAT 00301 and KAT 00309 were less sensitive to waterlogging but KAT 00308 was more sensitive to waterlogging. KAT 00301 and KAT 00309 should be improved to waterlogging-tolerant varieties through breeding. Green gram farmers should plant either KAT 00301 or KAT 00309 to minimise losses due to waterlogging. Master's Thesis

Synthesis and characterization of phosphate Geopolymers of pumice and medical waste incinerator fly ash fractions: methylene blue adsorption and recyclability studies.

Wed, 01 Jan 2025 00:00:00 GMT

Synthesis and characterization of phosphate Geopolymers of pumice and medical waste incinerator fly ash fractions: methylene blue adsorption and recyclability studies. ONYANGO, Collins Odongo Methylene blue (MB) is a toxic dye used mainly in the textile industry as a fabric colourant. Medical waste incinerator fly ash (MWI-FA) is a toxic waste with unresolved disposal challenges. The general objective of this study was to synthesize composite geopolymers of pumice with fractions of MWI-FA, and to evaluate the effect of the fractions on the physicochemical and adsorptive properties of the geopolymers for the abatement of MB from water. Four composites, GP-0, GP-10, GP-20 and GP-30 were synthesized from pumice, substituted with fractions of 0, 10, 20 and 30% w/w of MWI-FA respectively, followed by a phosphoric acid activation. The adsorptive performance of the geo-composites was evaluated for the abatement of MB, assessing the effect of the MWI-FA fractions on this performance. Material characterization revealed the formation of new functional groups such as –Si-O-P-O-T- and -Si-O-P- bonds, confirming geopolymer formation, and the evolution of new mineral phases tobermorite and heulandite, attributable to the incorporation of MWI-FA. Some physicochemical dissimilarities resulting from the incorporation of the fractions of the adjuvant were also observed. Furthermore, geopolymerization with 10% MWI-FA increased the specific surface area (SSA) of the precursors, but this diminished proportionately with increased MWI-FA fractions. The adsorption kinetics was best described by the pseudo-second order kinetic model, with the rate constant, (K2), increasing linearly with the rate of incorporation of MWI-FA. Thermodynamically, the results show that the adsorption process was enthalpy-driven, exothermic (negative ΔH values) and a physisorption process (ǀΔHǀ and Ea < 40 kJmol-1). Gibbs free energy, ΔG < 0, suggested a spontaneous and feasible adsorption process, with the adsorption spontaneity increasing linearly with temperature. The equilibrium data was best described by the Sips isotherm model. The maximum adsorption capacities of the geopolymers, ~31 mg/g, were indistinguishable despite the decline in SSA with increase in MWI-FA. MWI-FA provided new energetically favorable adsorption sites compensating the diminished SSA. Hot water showed good potential to regenerate the spent geopolymers twice, with up to 76.9% recovery. The adsorption of MB diminished considerably under saline conditions. The composite geopolymers provide an acceptable strategy for stabilization of up to 30% MWI-FA without compromising their chemical stability or adsorptive properties. The study recommends the incorporation of up to 30% MWI-FA, with sufficient aluminosilicate composition, in the pumice-based phosphate geopolymers for the sequestration of MB as a dual waste management strategy. Masters's Thesis

Evaluation of phsysicochemical, bacterial and fungal parameters of river Kibos water in Kisumu county, Kenya

Wed, 12 Nov 2025 00:00:00 GMT

Evaluation of phsysicochemical, bacterial and fungal parameters of river Kibos water in Kisumu county, Kenya OLUOCH, Nashon Okoth Wastewater discharges in river water is a major source of fecal microorganisms and poor water quality. Most important bacterial diseases are transmitted through water. River Kibos water quality is constantly changing due to waste water discharge from industries and the surrounding agricultural farms and settlements. Toxic wastes, chemicals and pathogens in the river water pose health risks to people using river water for drinking and recreation activities. Information on the effects of the season, water level, degree of eutrophication on physicochemical and microbial parameters of river Kibos is limited. The main objective of this study was to evaluate the physicochemical, bacterial and fungal parameters of River Kibos water. Specific objectives were to determine physicochemical parameters (pH, DO, temperature, turbidity, TDS, Nitrates, phosphates, BOD, ORP, Specific conductivity, COD and salinity), to characterise the fungi and bacteria of River Kibos water, to determine the fungal and bacterial population, and to determine the relationship between physicochemical and microbial parameters. Water samples (72) were collected for a period of 2 months three times per month from the river at four sampling sites randomly selected for wet (April to May 2019) and dry (February to March-2019) season in triplicates: The sites were Katieno I, Katieno II, Kotunga and Kibos Prison Bridge. The water was drawn slightly below the surface near the river edge. The water samples were preserved in an ice box at 4˚C to avoid destabilisation and fixed using acidic Lugols solution during transportation to the laboratory for analysis(You need to explain a bit how the samples were handled before the bacteria culturing)Bacteria were cultured using Nutrient Agar while fungi were cultured using Potatoe Dextrose Agar. Identification of bacteria and fungi was done using the standard microbiological techniques. Microbial count was determined by colony counter. Physicochemical parameters (temperature, DO, ORP, salinity, turbidity, specific conductivity, pH) were determined insitu by multiparameter instrument while nitrates, Phosphates, COD and BOD), were determined at the Maseno University microbiology laboratory. Data on physicochemical and microbial parameters was subjected to analysis of variance. Means were separated and compared using Pearson’s LSD at p≤0.05. Physicochemical parameters for dry season were: pH 7.4633, turbidity 249.92NTU, COD 0.83mg/l, NO - 3 3.623mg/l and PO - 4 2.4958.Wet seasons were; pH 11.0017, turbidity 341.58 NTU, COD 0.68 mg/l, NO - 3 3.89 mg/l and PO 4- 3.6625mg/l.Nine bacteria; Klebsiella spp, E.coli, Shigella spp, Salmonella typhi, Pseudomonas aeriginosa, Enterobacter cloacae, Shigella flexneri, Proteus spp and Staphylococcus spp. And Fungi ;Alternaria tenuissima, Aspergillus tubingensis, Penicillium citrinum and Penicillium crustosum. Bacterial and fungal counts in wet season was 50.25 and 141 cfu/ml respectively while for wet season were 12.5 and 51.33 cfu/ml respectively. The parameters were above the WHO and NEMA limits. The findings indicate that the water is polluted and hence a potential threat to human health. The water should be treated before human consumption. Master's Thesis

Temperature and composition effects on charge transport in pbdb-t-2cl: ieico-4f solar blends for next-generation organic photovoltaics

Wed, 12 Nov 2025 00:00:00 GMT

Temperature and composition effects on charge transport in pbdb-t-2cl: ieico-4f solar blends for next-generation organic photovoltaics AKINYI, Elizabeth Odunga Organic photovoltaics (OPVs) based on non-fullerene acceptors (NFAs) have achieved ~18 % power-conversion efficiency, benefitting from superior thermal stability and broader absorption compared to fullerene acceptors (FAs). Despite these advances, the performance and stability of OPVs remain strongly influenced by blend composition and temperature, which affect charge transport and recombination. The main objective of this study is to investigate the influence of blend composition on optical, morphological, electrical properties and the effect of temperature variation on photoluminescence properties of PBDB-T-2CL: IEICO-4F for organic photovoltaics application and the specific objectives are; To investigate the optical and morphological of pristine PBDB-T-2CL and IEICO-4F thin films, to analyze the effect of IEICO-4F dopant on optical, morphological, and electrical properties of PBDB-T-2CL: IEICO-4F thin films and to evaluate the effect of temperature variation on photoluminescence properties of PBDB-T-2CL: IEICO-4F thin films. Specifically, the bulk heterojunction (BHJ) structure formed by donor-acceptor blend was analyzed using temperature-dependent PL to evaluate charge transfer dynamics across different blend ratios. Spin coated thin films were characterized using ultraviolet-visible (UV-Vis) spectroscopy, atomic force microscopy (AFM), PL spectroscopy and four-point probe measurements. Data analysis was performed using Origin software. The UV-Vis spectra revealed that PBDB-T-2CL exhibited a primary absorption peak near 620 nm, while IEICO-4F showed complementary absorption at ~ 860 nm and the blends forms four characteristic peaks at 568 nm, 620 nm, 817 nm and 833 nm effectively broadening the spectra and enhance photo harvesting. Temperature – dependent PL analysis showed suppressed radiative recombination and enhanced charge transfer with increasing annealing temperature, particularly in the blends. AFM measurements indicated strong morphology dependence: pristine PBDB-T-2CL film were smooth (root mean square ≈2.28 nm), IEICO-4F film were rougher (root mean square ≈5.18 nm), while the optimized 70:30 blend exhibited the finest morphology (root mean square ≈1.398 nm ). These morphology features translated into distinct device characteristics. The 50% IEICO-4F composition achieved the highest PCE of 2.12 %, with a short circuit current density (Jsc) of 9.6 mA/cm2, open circuit voltage (Voc) of 0.60 V, and fill factor (FF) of 36 %. In contrast donor-acceptor blends showed reduced efficiencies (≤1.70 %), correlating with roughness and recombination losses. In conclusion, the study demonstrates that broad optical absorption, efficient charge transfer, favorable nanoscale morphology, and stable photovoltaic response are the key thin film properties supporting high efficiency bulk heterojunction and flexible thin film OPV devices. These finding proved experimental evidence that fine donor-acceptor morphology is crucial to balance charge generation and transport, offering insights for the design of next generation OPVs. Master's Thesis

Surveillance and influence of application rates and post-application harvest durations on imidacloprid residue levels in Solanum lycopersicum fruits of Kimira-Oluch, Kenya

Wed, 12 Nov 2025 00:00:00 GMT

Surveillance and influence of application rates and post-application harvest durations on imidacloprid residue levels in Solanum lycopersicum fruits of Kimira-Oluch, Kenya ACHIENG, Roselyne Omondi Tomato, (Solamun lycoperscicum) is a widely grown and consumed fruit-vegetable. It is susceptible to pest infestations that is usually controlled by pesticides use, especially imidacloprid (IMI), whose residues negatively impacts the environment and human health. Despite its low toxicity to humans, IMI bioaccumulation causes human health issues. Although widely used in Kenya, IMI use was banned by EU since it contributed to bee population decline. Even though exported agricultural products are often screened to meet international market limits, it is not practiced for locally consumed produce, this may lead to consumer exposure and subsequent poisoning. There is a need to compare IMI residue levels in local produce with EU/Codex-MRL to ensure safety and conformation to required standards. Kimira-Oluch Smallholder Farm Improvement Project (KOSFIP) is an irrigation scheme producing tomatoes in Homa Bay County. Farm gate tomatoes from KOSFIP have not been evaluated for safety and/or if they meet the EU/Codex-MRLs. It is not documented if KOSFIP farmers observe Good Agricultural Practices (GAPs) or IMI residue levels at farm-gates meet EU/Codex-MRL. Sometimes farmers use higher IMI concentrations and/or fail to observe minimum pesticide post application period (PAP). IMI recommended rate and PAP used at KOSFIP were developed in different environments. It is not known whether they suit the KOSFIP environment and/or influence residual IMI. This study assessed IMI residue levels in tomatoes at farm-gates and compared the levels with EU/Codex limits; determined influence of application rate and PAP on residue levels in KOSFIP tomatoes. Cross-sectional survey using random sampling method was used to sample tomato farmers applying imidacloprid. A 4x5 split-plot design in RCBD layout replicated thrice was used to determine effects of rates (0, 2.5, 5, 7.5 g/20L) and PAP (0, 2, 4,7,10 days) on IMI levels. Samples were prepared by QuEChERS method, residues analysed using LCMS/MS and data subjected to ANOVA using GenStat program. Results were compared with EU (0.3 mg/kg and Codex (0.5 mg/kg) limits. Approximately 62.9% of farm-gate samples had residues below EU-MRL and 92.9% below Codex-MRL, demonstrating most farmers were observing GAPs. Imidacloprid residues increased (p≤0.05) with high application rates and short PAP. Rates higher than the recommended had residue levels above EU-MRL. Recommended rate of application (5 g/20L) and PAP (3 days) are suitable for use in KOSFIP. Continued use of IMI at KOSFIP should be done according to GAPs and regular monitoring of GAPs implementation be prioritized. Master's Thesis

Enhancing sustainable construction through lime and water hyacinth ash -modified compressed earth blocks with improved acoustic properties

Tue, 11 Nov 2025 00:00:00 GMT

Enhancing sustainable construction through lime and water hyacinth ash -modified compressed earth blocks with improved acoustic properties OUMA, Justus Juma Modern construction materials must meet a myriad of requirements, including sustainability, structural integrity, thermal efficiency, and acoustic performance. This study assesses the urgent need for eco-friendly construction materials by investigating the potential of using a blend of lime and water hyacinth ash (WHA) as binders in locally sourced soils from Mayenje ward, Busia County. The primary objective was to fabricate Compressed Soil-Lime-Water Hyacinth Ash (CSL-WHA) blocks with suitable acoustic absorption properties for sustainable building and construction. The specific objectives of this study were as follows; (i) To fabricate compressed earth blocks using a binder mixture of lime and water hyacinth ash, ensuring uniformity and structural integrity (ii) To evaluate the acoustical properties of CSL-WHA blocks by recovering key parameters through inverse modeling of transmission data (iii) To assess how binder ratios (lime vs. WHA) influence acoustic properties of CSL-WHA blocks and (iv) To examine the effect of compaction pressure on the acoustic properties of the blocks. The study delved into the feasibility of acoustical modeling for parameter retrieval, ultimately evaluating the potential of CSL-WHA blocks to meet specified acoustic requirements. A series of sixteen formulations were evaluated across four compaction pressures (25–100 bar) to assess the influence of binder composition and key acoustic parameters, including porosity, airflow resistivity, tortuosity, and viscous characteristic length. The results showed that moderate WHA (≤5%) with high compaction pressure (≥75 bar) could yield balanced porosity (~0.30–0.36) while achieving ideal air flow resistivity, tortuosity and viscous characteristic length ranges for sound absorption, striking a balance between acoustic performance and strength. Inverse modeling using the Johnson-Champoux-Allard-Lafarge (JCAL) framework enabled non-destructive recovery of intrinsic acoustic parameters. These findings offer a design matrix for balancing acoustic absorption and mechanical performance, supporting tailored applications in partition walls, facade systems, and low-frequency noise control. Furthermore, the study pioneers the valorization of invasive water hyacinth biomass for acoustic damping, providing a foundation for localized standardization and contributing to circular economy goals. The integration of WHA as a partial binder advances sustainable construction practices, reinforcing material innovation within environmental and acoustic design frameworks. Master's Thesis

Effect of curing temperature on geopolymers from solid waste incinerator fly ash for removal of bromocresol green dye from water: synthesis, kinetics and thermodyanimics

Mon, 01 Jan 2024 00:00:00 GMT

Effect of curing temperature on geopolymers from solid waste incinerator fly ash for removal of bromocresol green dye from water: synthesis, kinetics and thermodyanimics OWINO, Eugene Kevin Bromocresol green (BCG) dye is extensively used in the textile and medical fields. However, the excessive and uncontrollable usage of this dye has resulted in contamination of water sources, endangering both aquatic life and human beings, hence the need for an urgent remedy. Geopolymers have been proposed as suitable adsorbents for removing various water pollutants due to their excellent adsorption capabilities compared to conventional treatment methods. The adsorption rates and capacities of geopolymers have been shown to depend on their structural, morphological, and compositional characteristics, which can be controlled by preparation conditions. Nonetheless, there is no available data on the influence of curing temperature on the structural, morphological and composition of solid waste incinerator fly ash (SWI-FA) based geopolymer adsorbents. Furthermore, although SWI-FA geopolymer-based adsorbent has been used in the removal of cationic, methylene blue dye from water, no study has reported on its interaction with an anionic dye. Thus, the aim of this work was to determine the suitability of SWI-FA for geopolymer production, and the effect of curing temperature on the composition, structural, morphological, and adsorption characteristics of SWI-FA based geopolymers for the removal of bromocresol green (BCG), an anionic dye from water. Alkali-activated SWI-FA geopolymer samples (GP30, GP50, GP70 and GP90) were prepared at curing temperature of 30 ° C, 50 ° C, 70 ° C, and 90 ° C, respectively. The SWI-FA and the geopolymers were characterized for morphology, elemental composition, functional groups, crystalline phases, and pH of point of zero charge (pHPZC). The effect of adsorption parameters namely initial dye concentration, pH, contact time, and temperature were examined. The EDS analysis results indicated presences of C, O, Al, Si, and Ca elements in SWI-FA, GP30, GP50, GP70, and GP90, and a variation in Si/Al ratio in the geopolymers as curing temperature was increased. The SEM results revealed morphological changes with curing temperature. The FT-IR analysis revealed a shift in the main band at 991 cm-1 due to asymmetric vibrations of Si-O-T (T=Al/Si) in SWI-FA to lower wavenumber in the geopolymers. The XRD analysis confirmed changes in crystalline phases of the geopolymers while the pHPZC of the geopolymers remained unchanged at 6.8. The kinetic data were best described by the pseudo-second order model (R2>0.99) while Langmuir isotherm model presented the best fit to the equilibrium data. From Langmuir isotherm model the maximum adsorption capacity for BCG dye uptake increased with curing temperature from 41.70 mg/g to 515.5 mg/g for GP30 and GP90, respectively. The thermodynamic parameters; namely enthalpy (ΔH ), Gibbs free energy (ΔG ), entropy (ΔS ) and activation energy (Ea) indicated that BCG adsorption processes is spontaneous, exothermic, physical (Ea kJ/mol and ΔH kJ/mol) and enthalpy-driven. The adsorption mechanisms controlling BCG adsorption onto the geopolymers included hydrogen bonding and strong electrostatic interactions. The results of this present study highlighted the opportunity of recycling SWI-FA and the potential of the synthesized SWI-FA based geopolymer adsorbents in effectively treating BCG dye-contaminated water. Master's Thesis

Phytochemical composition and bioactivity of extracts of Adenia lobata, Ipomoea aquatica, and Rubia cordifolia against Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus

Mon, 10 Nov 2025 00:00:00 GMT

Phytochemical composition and bioactivity of extracts of Adenia lobata, Ipomoea aquatica, and Rubia cordifolia against Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus JUMA, Meshack Mayianda Emergence and spread of antimicrobial resistance (AMR), is of great concern to the global health, necessitating the search for new therapeutic agents. Candida albicans, Pseudomonas aeruginosa and Staphylococcus aureus are among the serious AMR pathogens worldwide. Furthermore, AMR infections are associated with higher levels of oxidative damage in the human cells which is linked to various diseases, including cancer and cardiovascular diseases. Medicinal plants are of significant importance worldwide, serving as alternatives to modern medicine. Plant extracts contain phytochemicals, such as phenolic compounds, which exhibit bioactivities including antioxidant and antimicrobial activities. Antioxidants prevent oxidative stress in human cells, aiding in the management of oxidative stress-related diseases whereas antimicrobials kill or inhibit the growth of microorganisms, helping in managing infectious diseases. Despite several benefits of medicinal plants in herbal medicine, there is insufficient scientific data to support the use of the herbal drugs. Though a lot of studies have dealt with the studies for antioxidant and antimicrobial drugs from plants, there is less information on antioxidant and antimicrobial activity especially from Adenia lobata, Ipomoea aquatica, and Rubia cordifolia against Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus. This study was conducted at Maseno University and Kenya Marine and Fisheries Research Institute. The objectives of the study were to determine (i) the phytochemicals present in leaf, stem, and root extracts of the selected climbers; (ii) determine the antioxidant activity of the extracts and (iii) determine the effect of the extracts on the growth of the specified test organisms. A. lobata, I. aquatica, and R. cordifolia samples were collected using targeted random sampling method from Kisii (0°54'38.7"S 34°48'28.95"E), Lake Victoria shorelines-Kisumu City (0°7'33"S 34°44'33.6"E), and Maseno University farm (0°0'32.6"S 34°36'28.6"E) respectively. The samples were separated into leaf, stem and root parts which were air-dried in the shade, ground into powder and then soaked in methanol. Thereafter, filtration was done and the extracts concentrated. Phytochemical analysis was conducted to test the presence of saponins, tannins, terpenoids, steroids, flavonoids, alkaloids, cardiac glycosides, and anthraquinones. Thin layer chromatography (TLC), was conducted as a semi-quantitative phytochemical analysis. The antioxidant activity was assessed using 2, 2-diphenylpicryl-1-hydrazyl free radical scavenging method with ascorbic acid as reference standard. Microbial growth was assessed using the disc diffusion method at 25, 50, 75, and 100 mg/ml concentrations. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) were also determined. The antioxidant and antimicrobial assays were done in triplicates in a completely randomized design. Data collected was subjected to analysis of variance (ANOVA) followed by post hoc tests. Means were separated and compared using the least significant difference (LSD) at P≤0.05. Phytochemical analysis revealed presence of alkaloids, tannins, terpenoids, steroids, glycosides, saponins, flavonoids, and anthraquinones in the extracts. TLC analysis indicated R. cordifolia leaf extract had the highest number of phytochemical spots (14), while A. lobata and I. aquatica root extracts had the lowest spots (2). A. lobata root extract showed relatively high antioxidant activity with IC50 value of (116.25 μg/ml), and I. aquatica roots had lowest antioxidant activity of (355.16 μg/ml). The extracts significantly inhibited the growth of the three test organisms. The largest zones of inhibition were observed in 100 mg/ml R. cordifolia leaf extract against P. aeruginosa (21.00 mm), and S. aureus (15.57 mm), and 100 mg/ml in R. cordifolia root extract against C. albicans (11.67 mm). The extracts exhibited significant bacteriostatic and fungistatic activity. MIC values for R. cordifolia extracts against C. albicans was 5 mg/ml for both leaf and root extracts and 10 mg/ml for the stem whereas for both P. aeruginosa and S. aureus were all at 10 mg/ml. The study has demonstrated that A. lobata roots is a potential source of antioxidants. R. cordifolia has been shown to be active against C. albicans, P. aeruginosa and S. aureus. Bioactive activity in plants is primarily linked to phytochemicals. The study has revealed that the extracts from these climbing plants can be used as potential antioxidant and antimicrobial agents for the development of new drugs. With this evidence of bioactive secondary metabolites, there is need for further studies to isolate and characterize phytochemicals associated with these plants. Master's Thesis