Aims: The study aimed to synthesize silver nanoparticles (AgNPs) from aqueous AgNO3 using phytochemicals present in Pleurotus ostreatus and assess the AgNPs antibacterial activity on Bacillus subtilis and Providencia rettgeri. Study design: Experimental/Analytical. Place and Duration of Study: Bells University of Technology between December 2020 and August 2021. Methodology: The mushroom was washed, dried, pulverized and 5g stirred into 100ml deionized water. The solution was sonicated using ultrasonic cleaner at 40 oC for 40 min, centrifuged at 4000 rpm for 10 min. The supernatant was filtered, and 1ml filtrate was mixed with 9 ml of 10mM AgNO3. After the reaction period, the mixture was centrifuged at 15,000 rpm for 15 min. The residues were washed thrice with deionized water and dried. Synthesis of AgNPs was monitored by UV–Vis spectrophotometer, characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction analysis. Antibacterial analysis was done by agar well diffusion using gentamicin as control. Results: A dark brown colour change and UV visible spectroscopy peak at 400 nm confirmed the formation of AgNPs. Fourier transform infrared spectroscopy analysis showed the presence of functional groups involved in the reduction of AgNO3. GCMS performed on the methanolic extract of Pleurotus ostreatus showed the presence of 37 organic compounds, among them were cathecol, hydroquinone and phenols etc. Antimicrobial activity revealed that AgNPs inhibited the growth of B. subtilis and P. rettgeri. Conclusion: The study revealed that Pleurotus ostreatus effectively synthesized AgNPs and the AgNPs inhibited the growth of Providencia rettgeri and Bacillus subtilis and can play major roles in the field of medical and pharmaceutical nanotechnology.
Aims: Lead is a heavy metal pollutant that persists in the environment, has no biological function, and is potentially toxic to microorganisms. The study examined the effect of lead on the morphology and genetic profile of Pleurotus tuber-regium, an edible mushroom. Study Design: Experimental study design. Place and Duration of Study: Bells University of Technology between December 2017 and August 2018. Methodology: P. tuber-regium sclerotium was planted in loamy soils polluted with PbO (50, 80, and 100 mg/kg). The effect of the lead was assessed by recording time for mushroom emergence, fresh fruitbody weight, stipe and pileus diameter, % protein, %ash, and molecular profile of mushrooms harvested from polluted soils against a control. Extracted DNA was amplified with ITS1 and ITS4 universal primers; amplicons were visualized with a UV Bio-Rad illuminator. Results: Lead had varied influences on the morphometry. The fruitbody emergence was fastest in polluted soils and significantly different from the control. Fruiting occurred after 13.23±0.76, 5.41±0.88, 9.33±0.75 and 11.01±1.06 days in 0, 50, 80 and 100 mg/kg Pb polluted soils respectively. The fresh weight, stipe, and pileus diameter were significantly different at 50 mg/kg compared to the control. The range in values was 8.57±0.75 – 15.21±0.85g, 9.30±0.89 - 14.40±0.99mm, and 3.33±0.75 - 9.60±0.57cm respectively. The %protein and %ash contents were higher in mushrooms from polluted soils. Lead accumulated in polluted soils but the bioaccumulation coefficient was low. DNA profile showed variations in amplicon sizes. Conclusion: The study revealed that continuous exposure of Pleurotus tuber-regium to lead caused varied morphological and genetic changes. It led to increased fresh weight, stipe diameter, pileus diameter, and variation in DNA amplicons. The implication is that lead could cause variations in the morphology and genetic composition of P. tuber-regium.
Aims: Mushrooms are health-food used as food supplements and fortification but are susceptible to microbial spoilage due to high moisture content and nutrient status. Fresh mushrooms sometimes show signs of spoilage after harvest and makes storage difficult. The objective of the study was to identify and characterize bacteria and fungi associated with three fresh edible mushrooms, under ambient and cold temperatures. Methodology: The study was conducted at the Bells University of Technology, Nigeria, between December 2020 and October 2021. Pleurotus ostreatus and Calocybe indica fruitbodies were procured from the Federal Institute of Industrial Research Oshodi while Pleurotus tuber-regium fruitbodies were obtained from sclerotia planted in loamy soil. The fruitbodies were kept at ambient (28oC) and cold (15oC) temperatures respectively. The bacterial and fungal counts on each of the mushrooms were taken at 0,3, 5, and 7 days after harvest. The isolated bacteria were identified by conventional methods; Analytical Profile Index (API) 20E kits (BioMerieux), while Fungi were identified by morphological features and PCR amplification using ITS 1f/ ITS 4r universal primers. Results: The bacterial and fungal counts on the fruitbodies ranged from 5.7 log CFU/ml – 6.3 log CFU/ml and 5.0 log CFU/ml – 5.9 log CFU/ml respectively. Seven genera of bacteria isolated were gram-negative bacteria. At ambient temperature, Pseudomonas aeruginosa, Enterobacter asburiae, Klebsiella oxytoca, Klebsiella ornithinolytica, Serratia marcescens, Chryseobacterium meningosepticum and Cedecea davisae were isolated while Enterobacter cloacae, Enterobacter sakazakii and Citrobacter braakii were isolated at cold temperature. Aspergillus, Penicillium, and Fusarium were isolated at both temperatures while Alternaria was isolated at ambient temperature. Conclusion: Isolated bacteria and fungi were mostly enteric pathogens and potential mycotoxin-producing fungi. This is an indication that strict hygiene and control measures should be put in place during the production and storage of these mushrooms in order to improve the quality and food safety of fresh mushrooms in Nigeria.
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