Molecular Characterization of Aflatoxigenic Moulds and Effects of Processing on Aflatoxin Contamination of Some Wheat Mills from Northern Nigeria

Simple item page
dc.contributor.authorWARTU, JOSEPH REUBEN
dc.date.accessioned2018-09-25T14:02:55Z
dc.date.available2018-09-25T14:02:55Z
dc.date.issued2017-07
dc.descriptionA THESIS SUBMITTED TO THE SCHOOL OF POST GRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY DEGREE IN MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY, FACULTY OF LIFE SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIAen_US
dc.description.abstractAflatoxins are carcinogenic and genotoxic secondary metabolites that represents serious health risk to both human and animals. Standard methods were used to determine total moulds viable count and some physicochemical parameters on in-process and major store samples. ELISA technique was employed to detect and quantify total aflatoxins from the samples. While yeast extract sucrose agar was modified with 0.3% cyclodextrin and 0.6% sodium desocholate to detect aflatoxigenic strains, multiplex PCR was used to amplify the key genes (aflR-1, omt-A, ver-1, nor-1) that code for enzymes involved in aflatoxin biosynthetic pathway. The nucleotide sequences obtained from AFL2T was used for phylogenetic studies. The mean moisture of In-process wheat products, such as wheat flour (13.90±0.37%) was significantly higher than that of major store samples (13.25±0.25%). In-process and major store samples had Aspergillus flavus as the most frequent occurring moulds (75.0 and 79.3%) respectively and least by Aspergillus fumigatus (3.0%). The predominant aflatoxigenic strain was Aspergillus flavus (37.7%) and 43.0% from in-process and major stores respectively. Bran had the highest percentage of aflatoxigenic moulds in both in-process (66.0%) and major stores (78.0%), while wheat flour had the least in-process (17.5%). The study had aflatoxin prevalence of 38, 21, 28, 39 and 89% for wheat, semolina, wheat flour, brown flour and bran respectively. As the extraction rate of wheat products such as wheat flour increased from 60 - 75%, the ash content and the total aflatoxin retention increases from 0.57 - 0.82%dm and 2.1- 65.9% respectively. The aflatoxin decontamination decreased from 98.0 - 34.1%. The effects of solid substrate fermentation on total aflatoxin contaminated wheat flour into leavened bread showed significant aflatoxin loss (55.2%) at pH 5.8 and 37oC/120 minutes fermentation with 44.8% aflatoxin retention. Further aflatoxin loss was recorded (58.6 – 72.4%) as the baking temperature increases from 180 – 220oC. Similar aflatoxin reduction after 48h of submerged fermentation of wheat-sorghum composite `Kunun-zaki` was 18.9 and 52.90% for refrigerated and ambient temperature storage respectively. Quadruplet PCR pattern was consistent at 1032, 797, 537 and 400 bp with all the aflatoxigenic strains indicating amplification of the four genes (aflR-1, omt-A, ver-1 and nor-1) of the aflatoxin biosynthetic pathway, whereas the non-aflatoxigenic strains presented one, two and three banding patterns. The frequency of occurrence of aflatoxin biosynthetic gene in non aflatoxigenic strains were: nor-1 (73.3%), ver-1 (53.3%), omt-A (40.0%) and aflR-1 (13.3%). Enough homology was found through alignment of AFL2T gene sequences with standard aflR-1 of NCBI gene bank. The gene AFL2T nucleotide sequence generated dendogram produced two main clusters. All the twelve isolates were similar in their morphological characteristics, but genetically varied. The strains differentiated into groups and sub-group indicating general similarity. Some of the isolates varied greatly with visible mixtures of aflatoxigenic and non aflatoxigenic moulds and also with random mixture of in-process and store isolates with different genetic diversities at different leaf nodes within the two major clusters. Aflatoxigenic moulds counts and the total aflatoxin levels in some samples from this study could be a health threat to consumers.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/10541
dc.language.isoenen_US
dc.subjectMolecular Characterization,en_US
dc.subjectAflatoxigenic Moulds,en_US
dc.subjectEffects,en_US
dc.subjectProcessing,en_US
dc.subjectAflatoxin Contamination,en_US
dc.subjectWheat Mills,en_US
dc.subjectNorthern Nigeriaen_US
dc.titleMolecular Characterization of Aflatoxigenic Moulds and Effects of Processing on Aflatoxin Contamination of Some Wheat Mills from Northern Nigeriaen_US
dc.typeThesisen_US
Files
Original bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
Molecular Characterization of Aflatoxigenic Moulds and .pdf
Size:
1.51 MB
Format:
Adobe Portable Document Format
Description:
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
1.62 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
SCIENCE