ABSTRACT

Ogi is a popular fermented cereal gruel consumed mainly in the western part of Nigeria. Traditionally, ogi is normally administered to diarrhea patients to reduce the frequency of stooling. This study was undertaken to isolate, identify and determine the antimicrobial properties of Lactic Acid Bacteria (LAB) from fermented ogi. The antimicrobial activity of the cell free supernatant and the viable cells of the isolated LAB against food pathogen (Escherichia coli, Salmonella sp, Staphylococcus aureus, and Pseudomonas sp) were evaluated in this study using agar well diffusion assay. The organisms isolated were klebsiella sp, Escherichia coli, Streptococcus sp, Lactobacillus plantarum, Lactobacillus brevis and Enterobacter sp from fermented ogi in this study. Large zone of inhibition with cell free supernatant was observed against Salmonella species, Staphylococcus aureus, and pseudomonas species. This work has been able to show that the growth inhibition mediated by the fermented ogi on the test organisms is attributable to the presence of bioactive metabolites such as organic acid, hydrogen peroxide and bacteriocin produced by Lactic Acid Bacteria (LAB) present in the fermented ogi. However, ogi constitute a high antimicrobial properties against pathogenic microorganisms.

TABLE OF CONTENTS

Title page i

Certification ii 

Dedication iii

Acknowledgements iv

Table of contents v

List of tables ix

List of figures x

Abstract xi

CHAPTER ONE

1.0 Introduction 1 

1.2 Aims and Objectives 4

CHAPTER TWO

LITERATURE REVIEW

2.1 Ogi Overview, preparation and fermentation 5

2.2. Microbiology of cereal and millet fermentation 8

2.2.1. Lab in cereal and millet fermentation 8

2.2.2 Commercial production of ogi 10

2.3 Lactic acid bacteria (Lab) 13

2.3.1 History and occurrence of lab 14

2.3.2 Metabolic activities of lactic acid bacteria 15

2.3.2.1  Carbohydrate metabolism 15

2.3.2.2  Protein metabolism 16

2.3.2.3 Lipid metabolism 18

2.3.3 Health benefit of lactic acid bacteria 18

2.3.4 Technological bi-products of lactic acid bacteria; 22

2.3.5    Properties of lactic acid bacteria 24

2.3.5.1 Preservative property of lactic acid bacteria 24

2.3.5.1.1 Acid production 25

2.3.5.1.2 Exopolysaccharide formation 26

2.3.5.1.3 Bacteriocins Production 26

2.4       Bacteriocins of lactic acid bacteria              28

2.5       Bacteriocin application and prospect              28

2.6       Food spoilage microorganisms                                                                                    30              

CHAPTER THREE

3.0  Materials and methods              31

3.1 Study area                                                                                                                    31

3.2      Sample collection 31            

3.3      Sterilization of materials 31            

3.4      Normal saline preparation 32            

3.5      Media preparation for isolation of lactic acid bacteria. 32            

3.6      Microbiological analysis 32           

3.7 Identification of isolates            33           

3.8 Gram staining                        33            

3.9       Motility test (hanging drop method)                                                                          33 

3.10       Biochemical tests       34

3.10.1    Catalase test       34       

3.10.2    Coagulase test (slide test)                       34

3.10.3    Oxidase test       34       

3.10.4    Citrate utilization test       35       

3.10.5    Indole test       35

3.10.6   Voges-proskauer test       36

3.10.7   Methyl red test       36

3.10.8   Sugar utilization test       36 

3.10.9   Lactophenol Cotton blue staining             37

3.11    Food pathogen indicator bacterial 37

3.12    Screening of lactic acid bacteria for antibacterial activity 37

3.12.1 Antibacterial activity of the isolated lactic acid bacteria 37

3.12.2 Agar well diffusion method 38

 CHAPTER FOUR

4.0     Results 39

CHAPTER 5

5.1     Discussion                      46

5.2     Conclusion 48

5.3     Recommendation                                                                                                          49

          References                                                                                                                    50