EVALUATION OF ANTIMICROBIAL ACTIVITIES OF MICROORGANISMS ISOLATED FROM FERMENTED OGI

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 ﾿