ABSTRACT

The inhibition of food borne pathogens by exopolysaccharides of lactic Acid Bacteria isolates from Ugba was investigated. Food borne pathogens were isolated from three food types, Rice, beans and soup including Staphylococcus aureus, Escherichia coli, species of Proteus, Pseudomonas, Shigella, Salmonella and Bacillus. The prevalence of these isolates varied with Staphylococcus species being in all foods (100%), Bacillus (56%), Shigella(44.49%), Pseudomonas (33.3%), E.coli (22.2%), Proteus and Salmonella (11.1%) each. Three Lactic Acid Bacteria, L. plantarum, L. casei  and L. fermemtum were isolated from Ugba samples and had Exopolysaccharides yields of 121.67mg/l, 116.67mg/l and 98.33mg/l respectively. The antibacterial activity tests showed limited but significant activity of the EPS in the range of 8.33mm to 15.0mm diameter of inhibitions. Lactobacillus casei EPS had the highest level of inhibition against the isolates ranging from 9.00mm(Bacillus) to 15.0mm (Proteus) while L. plantarum EPS had least activity in the range of 0.00(Bacillus) to 12.67mm (Proteus). Comparatively, the Gram positive isolates were less susceptible to EPS (0.00mm to 11.67mm) than the Gram negative isolates (9.33mm to 15.0mm).There were also variations in the levels of activities of the EPS extracts from the different levels of activities of the EPS extracts from the different LABs from fermented foods like Ugba has potentials as good sources of bioactive metabolites with high utility value especially as supplement if not alternatives to commercial antibiotics.

TABLE OF CONTENTS

Title page i

Dedication ii

Acknowledgements iii

Table of Contents iv

Abstract v

CHAPTER ONE

1.0 Introduction 1

1.1 Aim 4

1.2 Objectives 4

CHAPTER TWO

2.0 Literature Review 5

2.1 Ugba

2.2 Lactic Acid Bacteria 7

2.3 Taxonomical Classification of Lactic Acid Bacteria 7

2.4 Occurrence of Lactic Acid Bacteria in Nature 8

2.5 Exopolysaccharide 8

2.6 Exopolysaccharide Producing Bacteria 9

2.7 Biosynthetic Pathways Leading To Exopolysaccharide Synthesis in Lab 11

2.8 Classification and Chemical Composition of Exopolysaccharide 13

2.8.1 Homo-exopolysaccharide 14

2.8.2 Hetero-exopolysaccharide 16

2.9 Exopolysaccharide Yields Produced By Lactic Acid Bacteria 17

2.10 Health Properties of Exopolysaccharide 18

2.11 Novel Applications of Exopolysaccharides from Lactic Acid Bacteria 19

2.12 Foodborne Bacterial Pathogens 20

2.12.1 Salmonella 20

2.12.2 Staphylococcus aureus 20

2.12.3 Clostridium botulinum 21

2.12.4 Shigella 21

CHAPTER THREE

3.0 Materials and Methods 21

3.1 Source of Materials 21

3.2 Media and Sample Preparations 21

3.2.1 Media Preparation 21

3.2.2 Sample Preparation 22

3.3 Isolation of Food Borne Pathogens 22

3.4 Characterization and Identification of Food Borne Pathogens. 23

3.4.1 Colony morphology. 23

3.4.2 Microscopic characteristics 23

3.4.3 Biochemical Reaction Tests 23

3.4.3.1 Catalase Test 24

3.4.3.2 Indole Test 24

3.4.3.3 Coagulase Test 24

3.4.3.4 Oxidase Test 24

3.4.3.5 Motility, Indole, Urease (MIU) 25

3.4.4 Carbohydrate utilization test 25

3.5 Isolation of Lab from Ugba 26

3.6 Extraction of Exopolysaccharide 26

CHAPTER FOUR

4.0 Results 27

CHAPTER FIVE

5.0 Discussion, Conclusion and Recommendations 35

5.1 Discussion 35

5.2 Recommendation 37

5.3 Conclusion 37

References 38