Antagonistic Activity Of Lactic Acid Bacteria Crude Extract Against Vegetable Spoilage Bacteria

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