Browsing by Author "Dhlamini, Z."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Cloning Cellulase Genes from Victoria Falls Rainforest Decaying Logs Metagenome
    (Sciendo, 2024) Nyathi, M,; Dhlamini, Z.; Ncube, T.
    The Victoria Falls rainforest is a protected site whose forest floors harbor a host of cellulolytic microorganisms involved in biomass degradation. This study collected decaying logs and soil from the rainforest for bioprospecting cellulases from their metagenomes. Metagenomic DNA was isolated from the compound sample. Degenerate cellulase primers were used to amplify cellulase genes in the metagenome. The resulting amplicons cloned into Z-competent Escherichia coli DH5α were analyzed by functional screening for the production of cellulase extracellularly. Functional screening of the clones resulted in one clone (Clone-i) testing positivefor extracellular cellulase production. Submerged fermentation of Clone-i was carried out for cellulase production. The cellulases were characterized to determine their activity’s optimum pH and temperature. The diversity of the cellulases produced by Clone-i was determined. Clone-i’s optimum enzyme activity was observed after 72 hours of incubation at 50°C and pH 5. Clone-i produced 80% more exoglucanases as compared to endoglucanases. The cel- lulolytic Clone-i’ isolate shows Victoria Falls rainforest’s potential as an enzyme bioprospecting site, reflecting that metagenomics is a valuable tool in microbial ecology.
  • No Thumbnail Available
    Item
    Molecular Characterization of Aflatoxigenic Aspergillus species in dried Traditional foods in Zimbabwe
    (Society of Education, 2014-01-10) Dangwa, N.; Mwenje, E.; Dhlamini, Z.; Siwela, A.H
    The presence of aflatoxin producing Aspergillusspp in sixty samples of six selected traditional foods sold on the Bulawayo open market in Zimbabwe was investigated. Ten samples of each of the following commodities were bought from the market; dried groundnuts, dried cowpeas, dried maize, dried cowpea leaves, dried mopane worms and dried Cleome gynandra leaves and analysed for the presence of aflatoxigenic aspergillus. Moisture content of the samples was determined and another portion of the samples was plated on petri dishes containing Sabouraud Dextrose Agar (SDA) and incubated at 28 C. A total of 35 isolates was obtained and these were characterised according to their morphology as well as the type of aflatoxins they produced as determined by thin layer chromatography. Four distinct morphological groups were found and they were classified as Aspergillu sparasiticus (57%); Aspergillusniger (17%); Aspergillus tamarii (17%) and Aspergillusflavus (8%). These results were validated by using DNA primers of the structural genes, aflD (nor-1), aflM (ver-1) and aflP (omt-1) and the regulatory gene aflR to discriminate between aflatoxigenic and nonaflatoxigenic strains after amplifying DNA of the fungal strains. None of the isolates produced all the four genes involved in the aflatoxin biosynthetic pathway although they had shown positive results on the biochemical tests. Out of the 35 isolates obtained, 18 of them were aflatoxigenic and these isolates were from mopane worms (9), cowpeas (4), groundnuts (3) and Cleome gynandra (1). This investigation showed that dried traditional foods in Zimbabwe were contaminated by the aflatoxigenic fungus, Aspergillus, probably due to improper drying of the commodities, coupled by prevailing environmental conditions from packaging to the selling points.