ABSTRACT

The antagonistic activity of lactic acid bacteria crude extract against some vegetables spoilage bacteria was investigated.  Three lactic acid bacteria (LAB) Lactobacillus casei, Lactobacillus plantarum and Pedicoccus species, were isolated from Ogi, Ugba and Raw milk (Nunu) where their occurrence levels were 100%, 66.7% and 66.7% respectively. Six bacteria species were isolated from three vegetable types (Ugu, Oha and Water leaf) at spoiling stages, from three different markets (Umudike, Amawom and Ndoro). The isolate included Staphylococcus (100% occurrence), Pseudomonas (66.7%), Bacillus (88.9%), Erwinia (77.8%), E. coli (44.4%) and Proteus spp (33.3%). The supernatant crude extracts of the lactic acid bacteria demonstrated antagonism against the bacteria isolates from the spoilt vegetables but to varying extents. Crude extracts from L. plantarum caused inhibitions with diameters ranging from 6.67mm (Staphylococcus) to 10.3mm (E. coli) while the range of 11.33mm (Proteus and Erwinia) to 13.33mm (E.coli). Extracts from Pedicoccus species caused inhibition ranging from 6.3mm (Bacillus) to 13.67mm (Proteus). Also, the extract from both lactobacilli did not inhibit Bacillus while the extract of L. Casei did not inhibit Staphylococcus.  It was noted that all the crude extracts had inhibitory activity well below that of a standard antibiotic which ranged between 18.33 to 25.0mm in diameter. Nevertheless, the test extracts were recorded to have demonstrated antagonism against the vegetable spoilage bacteria and as such have potential for industrial application if properly harnessed.

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgements iv

Table of Contents v

List of Tables vii

Abstract viii

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study 1

1.2 Aims and Objectives 2

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Health implication of bacteria in vegetables 4

2.2  Pathogenic bacteria associated with vegetables 5

2.3 Vegetables and its nutritional value 6

2.4 Vegetables spoilage bacteria 7

2.5 Characteristics of spoilage micro organisms 10

2.6 Prevention and control measures 12

2.6.1 Pre-harvest 12

2.6.2 Post harvest factors 13

2.7 Lactic Acid Bacteria (LAB) 14

2.8 Antimicrobial property by lactic acid production 15

2.9 Bacteriocin Crude extract). 15

CHAPTER THREE

3.0  MATERIALS AND METHODS

3.1. Source of materials 18

3.2. Preparation of media 18

3.3. Isolation of spoilage bacteria vegetables 18

3.3.1 Isolation 18

3.3.2  Characterization of  Isolates 18

3.3.3 Sugar utilization test 22

3.4 Identification of isolates 22

3.5 Production of lactic acid bacteria extract 23

3.6 Antibacteria activity of lactic acid bacteria extracts 23

CHAPTER FOUR

4.0. RESULTS

CHAPTER FIVE

DISCUSSION, CONCLUSION AND RECOMMENDATIONS

5.1 Discussion 30

5.2  Conclusion 31

5.3  Recommendations 32

REFERENCES

APPENDIX