Articles, Conference and Workshop Papers Collection

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Chitosan enriched with ZnO–nanoparticles fabricated using Synadenium glaucescens (Pax) aqueous leaf extract maintains postharvest quality of banana
(Applied Food Research, 2024-09) Alinanuswe Joel Mwakalesi; Tlehema Gwandu Umbayda
Applications of edible coatings containing metallic nanoparticles for the preservation of post-harvest fruit quality have emerged as one of the most preferable strategies because of their enhanced antimicrobial properties. In the current study, zinc oxide nanoparticles were synthesized using Synadenium glaucescens leaf extract and added to chitosan for the post-harvest quality preservation of banana. The synthesized zinc oxide nanoparticles (ZnO- SydlNPs) were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental dispersive x-ray (EDX) and X-ray diffraction (XRD) techniques. The nanoparticles were found to form large particles due to aggregations of small particles of an average size of 11 ± 4 nm. The coating so- lution containing a mixture of chitosan and zinc oxide nanoparticles exhibited higher antimicrobial effects against Escherichia coli, Staphylococcus aureus, Puccinia asparagi and Candida albicans compared to chitosan. The inhibition diameters of chitosan and chitosan-ZnOSydlNPs against E. coli were 6 and 15 mm, respectively. Similarly, the average inhibition diameters of chitosan, chitosan-ZnOSydlNPs (0.1%) and chitosan-ZnOSydlNPs (0.3%) against Staphylococcus aureus, Puccinia asparagi and Candida albicans were 10 ± 2, 15 ± 0.5 and 16 ± 3 mm, respectively. The banana coated with chitosan-ZnOSydlNPs solutions exhibited higher titratable acid (maleic) than control and chitosan-coated samples. Additionally, banana coated with chitosan-ZnOSydlNPs lms showed lower total soluble solids, weight loss and ripening index compared to chitosan-coated and control samples. The ndings from the current study indicated that ZnOSydlNPs incorporated in polymeric materials (chitosan) could serve as a potential preservative of post-harvest qualities for banana and related fruits.
Effects of phosphoric acid concentration on properties of activated carbon from Strychnos spinose fruit shells
(Nature, 2026) John Chagu; Alinanuswe Joel Mwakalesi
The accumulation of agricultural wastes in the environment is an emerging challenge. Their thermochemical conversion to activated carbon represents an efficient form of utilization that minimizes the secondary pollution caused by conventional treatment methods, such as incineration and landfilling. This study reports the synthesis and characterization of activated carbon from an affordable, abundant, and underutilized source of Strychnos spinosa fruit shells. The activated carbon was prepared through chemical activation using phosphoric acid of different concentrations (30%, 60%, 100%, and 150%), followed by physical activation at 500 °C for 4 h. The influence of the activating agent concentrations on the properties of activated carbon, such as yield, moisture content, ash content and iodine number, was studied. Additionally, X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller and Infrared spectroscopy techniques were used to study characteristics of activated carbon. The results showed that the yield of activated carbon increased from 25.33% to 29.2% as the concentration of phosphoric acid increased from 30% to 150%. The increased acid concentration also increased the moisture content, ash content and iodine number of the activated carbon. The highest iodine number of 999 mg/g was obtained for the activated carbon with the surface area of 507.373 m²/g impregnated with 150% phosphoric acid. Similarly, the SEM images revealed larger pore sizes for activated carbon produced using 150% phosphoric acid compared to those produced using 30%, 60% and 100% phosphoric acid. The findings demonstrate that phosphoric acid concentration influences the properties and performance of the Strychnos spinosa fruit shell activated carbon.
Efficient and reusable activated carbon from aframomum angustifolium fruits’ shells for removal of ceftriaxone from aqueous solution: adsorption isotherms, kinetics, and thermodynamics studies
(Indonesian Journal of Chemistry, 2025-11) Baraka Alfaksad Kasazi; Alinanuswe Joel Mwakalesi; Emmy Solomon Lema
The accumulation of ceftriaxone antibiotics in aquatic systems is a growing global concern due to their potential risks to human and ecological health. The current study investigates the synthesis, characterization, and application of activated carbon (AC-FPAA-H3PO4) made from the shells of Aframomum angustifolium fruits. AC- FPAA-H3PO4 was synthesized using chemical activation (H3PO4, 4 M) followed by pyrolysis at 600 °C for 1 h and characterized using BET, FTIR, and SEM-EDX. AC-FPAA-H3PO4 exhibited a surface area of 1895.6 m2/g, which allowed for its reuse in 5 consecutive cycles without requiring active site regeneration. The optimal removal efficiency (97.8%) was achieved at pH 2, 298.15 K, 100 rpm, 20 g/L adsorbent dosage, and 200 mg/L ceftriaxone concentration. The adsorption process was described by Langmuir (R2 = 0.9862) and Freundlich (R2 = 0.9833) isotherms, and the kinetics were fitted to the pseudo-second- order model. The adsorption was spontaneous (ΔG = −6.80 kJ/mol) and exothermic (ΔH = −4.43 kJ/mol), with increased randomness at the solid-solution interface (ΔS = 7.69 J/mol K). The adsorbent demonstrated high efficiency in removing ceftriaxone from real water samples, including river water (99.36%) and well water (96.92%). The findings suggest AC-FPAA-H3PO4 is a promising adsorbent for removing ceftriaxone from an aqueous environment.
KOH-activated carbon from Aframomum angustifolium fruit shells for caﬀeine removal from aqueous solution
(Springer, 2025-12) Baraka Alfaksad Kasazi; Alinanuswe Joel Mwakalesi; Emmy Solomon Lema
This study reports on the preparation of activated carbon using Aframomum angustifolium fruit shells (FPAA) and its application for the removal of caffeine from aqueous solution. The activated carbon was prepared using KOH activation in a 1:2 ratio, followed by pyrolysis at 500 °C for 1 h. The activated carbon (AC-K) was characterized using the point of zero charge of potential of hydrogen (pHpzc), N2 adsorption–desorption analysis, scanning electron microscopy–energy-dis- persive X-ray spectroscopy (SEM–EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The surface of AC-K exhibited a mesoporous structure with an increased BET surface area from 335 to 407.6 m2/g. The classical method and response surface methodology (RSM) using Box–Bohnken design (BBD) were used to optimize the performance of AC-K to remove caeine from aqueous solutions. The results indicated that the adsorption aligned best with the Langmuir model (R2 = 0.996 and RMSE = 0.3531), indicating the formation of a monolayer film. In addition, the adsorption was described by the pseudo-second-order model (R2 = 0.995 and RMSE = 0.017). The highest caffeine removal eciencies were 78.67 and 90.40% as determined using classical and BBD methods, respectively. Therefore, the prepara- tion and use of an eco-friendly and previously unexplored precursor for activated carbon preparation is demonstrated in the current study. This study contributes to sustainable waste valorization while oering a promising alternative material for the removal of emerging contaminants such as caffeine from water systems.
Novel edible coating based on Macadamia Nut oil and chitosan to maintain the antioxidant and physical properties of tomato fruits
(Applied Food Research, 2024-06) Tlehema Gwandu Umbayda; Anthony Daniel Funga; Alinanuswe Joel Mwakalesi
Innovative approaches for extending the shelf life of tomatoes are required due to increased postharvest losses of climacteric-fruits. The use of edible coatings is recently considered as a promising approach due to their non- toxicity and affordability properties. The coatings form physical barriers that alter the internal atmosphere of the fruit and slow down a ripening process. The inuence of an edible coating comprising of chitosan and macadamia nut oil on the antioxidant and physical properties of tomato fruits is reported. The antioxidant and physical qualities of tomato fruits were investigated using different coating solutions. Various concentrations of macadamia nut oil, ranging from 1 % to 2.5 %, were used as independent coating solutions. Additionally, another set of coating solutions was prepared by mixing macadamia nut oil in the same concentration range (1 % to 2.5 %) with 1 % w/v chitosan. The tomatoes were dipped into the coating solutions and stored under a post- harvest shed (23.8–30 ◦ C, 65.8–97.5 % RH) for 20 days to monitor total phenolic content, total avonoid con- tent, ascorbic acid content, color, percentage weight loss, decay percentage, and shelf life after every 5-days interval. The results showed a signicant difference (P < 0.05) between coated and uncoated tomato samples. The coated tomatoes showed the signicant retention of total avonoid content, total phenolic content, hue angle and red-green (a*) compared to uncoated tomatoes. On contrast, the decrease of decay, weight loss, the lightness (L), blue-yellow (b*), chroma, and ascorbic acid content was lower for coated compared to control tomatoes. The ndings indicated that 1 % macadamia nut oil exhibited the highest retention of antioxidant and physical properties, and lowest decrease in ascorbic acid content from 0.014 mg/100 g on the 5th day to 0.0096 mg/100 g on the 20th day was observed. Thus, the ndings from this study suggest that the macadamia nuts can serve as a cheap and low-cost source of edible oil suitable for prolonging the shelf life of tomatoes and related fruits.
Screening anticancer activity by Brine shrimp lethality test of extracts of Annona stenophylla (Engl. & Diels), Strophanthus petersianus (Klotzsch) and Synadenium glaucescens (Pax)
(PLOS One, 2026-01) Roberto Luis Nhamussua; Faith Philemone Mabiki; Alinanuswe Joel Mwakalesi; Lyndy Joy McGaw
Cancer continues to be one of the main public health challenges, driving the search for new compounds with therapeutic potential. Medicinal plants represent a valuable promising source of bioactive metabolites, and the Brine Shrimp Lethality Test has been widely used as a preliminary tool to assess the toxicity of natural extracts, pro- viding clues to their possible anticancer activity. In this study, the cytotoxicity of the extracts of Annona stenophylla (Engl. & Diels), Strophanthus petersianus (Klotzsch), and Synadenium glaucescens (Pax) was investigated using the BSLT as a first step in screening for potential anticancer compounds. The plant materials were harvested in Tanzania and air-dried in the shade, and ground. The extracts were prepared by total sequential solvent extraction using cold maceration, starting with ethyl ace- tate, followed by methanol.
Synergistic effect of macadamia nut oil and Chitosan coatings on physicochemical characteristics of tomatoes during storage
(John Wiley & Sons Ltd, 2025-10) Tlehema Gwandu Umbayda; Anthony Daniel Funga; Alinanuswe Joel Mwakalesi
A signicant portion o globally produced ruits are lost between the armer and consumer, necessitating solutions like natural edible coatings or preservation due to their low cost and less toxicity. Tis study aimed to assess whether the combination o macadamia nut oil and chitosan posed synergistic eects on physicochemical properties o tomato ruits or the macadamia nut oil alone. A completely randomized design (CRD) with eight treatments was employed: S1 (control), S2–S4 (combined macadamia nut oil and chitosan coating), S5–S7 (macadamia nut oil coating), and S8 (chitosan). Te experimental setup was conducted over 20 days at rerigeration (4°C) and postharvest shed conditions (23.8°C–30°C, 65.8%–97.5% RH). Te coating solution made up o a combination o 2.5% v/v macadamia nut oil and 1% w/v chitosan showed signicant dierences (p ≤ 0.05) in slowing down the changes in pH rom 3.95 to 4.3, total chlorophyll content rom 0.19 mg/100 to 0.12 mg/100 mL, and lipid peroxidation rom 13.5 to 19.71 meq/kg. Moreover, coating solutions made by macadamia nut oil alone, especially with 1% v/v, showed the smallest increases in total soluble solids (SS) and total sugar content, and also they exhibited the smallest decreases in titratable acidity (0.64 to 0.08 g/L), ripening index (5.78 to 84.74), total carotenoids (17.02 to 24.585 μg/g), and rmness (355 N to 130 N). Comparative analysis indicated that 1% v/v macadamia nut oil had higher mean dierences (p < 0.05) or most physicochemical parameters than coating solutions comprising 2.5% v/v macadamia nut oil and 1% w/v chitosan. However, this nding highlighted that the combination o macadamia nut oil with chitosan oers a synergistic eect on specic crucial parameters (pH, total chlorophyll content, and lipid peroxidation) compared to macadamia nut oil alone. Further studies could investigate the an- timicrobial eect o tomatoes treated with a combination o macadamia nut oil and chitosan.
Unveiling the hidden risks: heavy metal concentrations in soil and vegetables irrigated with Kalobe wastewater stabilization ponds, Mbeya, Tanzania
(Journal of Food Protection, 2025-10) Azaria Stephano Lameck; Dickson Mlelwa; John Chagu; Victor Sanga; Melkizedeck Hiiti Tsere; Gisandu K. Malunguja; Alinanuswe Joel Mwakalesi
This study evaluated the concentrations of heavy metals in wastewater, soil, and tomatoes and Napa cabbage irrigated with efuent from the Kalobe Wastewater Stabilization Pond (KWWSP) in Mbeya, Tanzania. Human health risks were assessed using Chronic Daily Intake (CDI), Target Hazard Quotient (THQ), Hazard Index (HI), and Target Cancer Risk (TCR) indices. The results showed that cadmium (Cd) in all ponds was below the FAO/ WHO permissible limits, while lead (Pb) and chromium (Cr) were below detection levels. Heavy metals in soil were found in the order of Pb (5.95 mg/kg) > Cr (0.63 mg/kg) > Cd (0.25 mg/kg), all within FAO/WHO acceptable limits, indicating suitability for agricultural use. Cd levels in Tomatoes (0.14 mg/kg) and Napa cab- bage (0.40 mg/kg) exceeded permissible limits. Cr levels in the Tomato and Napa Cabbage were 1.87 and 2.10 mg/kg, respectively, and were close to the safety threshold, suggesting health concerns with long-term consumption. Cd exposure through vegetable intake was within but near acceptable limits, while Cr exposure, particularly for Napa cabbage, exceeded recommended safety thresholds. This resulted in elevated noncarcino- genic risks (THQ and HI > 1) and carcinogenic risks (TCR above the USEPA’s acceptable range). These ndings suggest that consuming wastewater-irrigated Tomatoes and Napa cabbage may pose human health risks. Continuous monitoring of heavy metals, safe irrigation alternatives, and cropping restrictions using inade- quately treated wastewater is essential to safeguard public health and long-term environmental sustainability.

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