Isolation And Identification Of Fungi Producing Mycotoxins From Rice Grains Sold In Umuahia Markets

ABSTRACT

The present research work explores fungi and mycotoxins associated with rice grains. Mycotoxins are secondary metabolites of molds that have adverse effects on humans, animals and crops that result in illnesses and economic losses. Total of 18 rice samples collected from different markets in Umuahia (Ubani, Orieugba and Ndioru) were analyzed. Six different fungi were isolated altogether namely; Aspergillus niger, Aspergillus flavus, Penicillium sp., Rhizopus sp., Fusarium sp. and Yeast sp. In the result for the percentage occurrence of fungal isolated in rice samples Yeast sp. accounted for 83.3%, followed by Aspergillus niger (50%), Aspergillus flavus and Penicillum sp. (38.9%), Rhizopus sp. (22.2%) and Fusarium sp. (16.7%). Mycotoxin production by isolated fungi was subsequently evaluated using the Thin Layer Chromatography (TLC) technique. In the results, mycotoxin assay revealed that only Aflatoxin was produced in this study. Not all fungi produced toxin. While Aspergillus flavus and A.niger produced Aflatoxin, Fusarium sp., Rhizopus sp., Penicillium sp., and Yeast sp., did not produce any toxin. The result of fungal load demonstrated that Mars rice brand from Ubani market recorded the highest count with 54 x 102 cfu/g, samples from Orieugba market showed that Royal stallion rice has the highest count of 37 x 102 cfu/g and Mars rice from Ndioru market equally recorded a high count (46 x 102 cfu/g) at P<0.05, this was a significant difference in the fungal count from samples of various markets. Detection of fungi and aflatoxins in rice poses a risk for consumer’s health owing to the fact that rice is highly consumed and it is necessary to check the rice grains before allowing distribution for public use.

TABLE OF CONTENTS

Dedication ﾿ i

Acknowledgement ﾿ ii

Table of Contents ﾿ iii-v

List of Tables ﾿ vi

Abstract ﾿ vii

CHAPTER ONE

1.0 ﾿ Introduction

1.1 ﾿ Background of the Study ﾿ 1-2

1.2 ﾿ Significance of the Study ﾿ 2

1.3 ﾿ Aim of the Study ﾿ 3

1.4 ﾿ Objective of the Study ﾿ 3

CHAPTER TWO

2.0 ﾿ Literature Review ﾿

2.1 ﾿ Historical Review of the Study ﾿ 4-5

2.2 ﾿ Nature of Mycotoxins ﾿ 5

2.3 ﾿ Types of Mycotoxins ﾿ 5-11

2.4 ﾿ Classification of Mycotoxin-producing Fungi ﾿ 12

2.5 ﾿ Routes of Contamination ﾿ 13

2.6 ﾿ Site of Infection of Mycotoxigenic Fungi in Rice Grains ﾿ 13-15

2.7 ﾿ Mycotoxigenic Fungi in Rice ﾿ 15-17

2.8 ﾿ Strategies for Prevention of Mycotoxin ﾿ 17-18

2.9 ﾿ Control Measures ﾿ 18-20

CHAPTER THREE

3.0 ﾿ Materials and Methods

3.1 ﾿ Sources of Materials ﾿ 21

3.2 ﾿ Sampling and Sample Preparation ﾿ 21

3.3.0 ﾿ Isolation of Fungi ﾿ 22

3.3.1 ﾿ Characterization of Fungi Isolates ﾿ 22

3.3.2 ﾿ Identification of Fungi Isolates ﾿ 22

3.4.0 ﾿ Screening of Rice for Mycotoxins ﾿ 22-23

3.4.1 ﾿ Thin Layer Chromatography (TLC) Method for Screening of Mycotoxins ﾿ 23-24

CHAPTER FOUR ﾿

4.0 ﾿ Results ﾿ 25

CHAPTER FIVE

5.0 ﾿ Discussion, Conclusion and Recommendation

5.1 ﾿ Discussion ﾿ 30-32

5.2 ﾿ Conclusion ﾿ 33

5.3 ﾿ Recommendation ﾿ 33-34

References

Appendix I

Appendix II

Appendix III

Appendix IV

Appendix V