Invitro Inhibitory Effect Of Bacteriocin From Lactic Acid Bacteria From Ugba (Pentaclethra Macrophyla Benth) Against Carrot (Daucus Carrota) Spoilage Bacteria

ABSTRACT

This work studied the in vitro inhibitory effect of bacteriocin from lactic acid bacteria (LAB) from Ugba against spoilage bacteria of carrot (Daucus carrota). Seven bacteria species were isolated from randomly selected spoilt carrot tubers from five (5) locations. The isolates and their respective occurrences Staphylococcus aureus (100%), Pseudomonas spp (75%), Proteus spp (40%), Serratia spp (80%), Bacillus spp (80%), Corynebacterium spp (15.3) and Escherichia coli (40%). Two lactic acid bacteria, Lactobacillus fermenti and Lactobacillus plantarum were isolated from Ugba and their crude bacteriocin extracts were used for tests. Result of pathogenecity test of the spoilt carrot bacteria isolates, showed only three isolates, Corynebacterium, Pseudomonas and Serratia species were confirmed to be pathogens of fresh healthy carrot tubers. The inhibitory effects of the crude bacteriocin extracts of the lactic acid bacteria isolates showed inhibitions of varied sizes against the pathogens in vitro. L. casei crude extracts generated inhibition zones of diameters in the range of 11.67mm (Corynebacterium) to 13.67mm (Serratia) while L. fermenti cause inhibitions of 10.67mm (Pseudomonas) to 12.67mm (Serratia). The inhibitory of L. plantarium crude bacteriocin extracts was in the range of 10.67mm (Corynebacterium) to 13.67mm (Serratia). The inhibitory activities of the lactic acid bacteria extracts were all lower than that of a standard antibiotic (control) which ranged between 18.67mm (Serratia) 22.0mm (Pseudomonas). The potentials of the crude bacteriocin extracts from lactic acid bacteria controlling carrot spoilage bacteria was observed in spite of the relatively low level of inhibitions.

TABLE OF CONTENTS

Title Page ﾿   ﾿ i

Certification ﾿ iii

Dedication ﾿ iv

Acknowledgement ﾿ v

Table of Contents ﾿ vi

List of Tables ﾿ vii

Abstract ﾿ ix

CHAPTER ONE

1.0 ﾿ Introduction ﾿ 1

1.1 ﾿ Aim and Objectives ﾿ 3

CHAPTER TWO

2.0 ﾿ Literature Review ﾿ 5

2.1 ﾿ Importance and Description of the African Oil Bean Tree ﾿ 5

2.2 ﾿ Preparation of Ugba ﾿ 5

2.3 ﾿ Lactic Acid Bacteria ﾿ 6

2.3.1 ﾿ Taxonomical Classification of Lactic Acid Bacteria ﾿ 7

2.3.2 ﾿ Occurrence of Lactic Acid Bacteria in Nature ﾿ 7

2.4 ﾿ Bacteriocins ﾿ 8

2.4.1 ﾿ Antimicrobial Property by Bacteriocin Production ﾿ 9

2.4.2 ﾿ Range of Activity ﾿ 10

2.5 ﾿ Classification of Bacteriocins ﾿ 11

2.5.1 ﾿ Class I ﾿ 11

2.5.2 ﾿ Class II ﾿ 12

2.5.3 ﾿ Class III ﾿ 13

2.5.4 ﾿ Nisin ﾿ 13

2.6 ﾿ Bacteriocin-Like Substances ﾿ 14

2.7 ﾿ Isolation and Purification ﾿ 15

2.8 ﾿ Methods of Purification ﾿ 16

2.8.1 ﾿ Purification of Class I Bacteriocins ﾿ 18

2.8.2 ﾿ Purification of class II bacteriocins ﾿ 19

2.8.3 ﾿ Purification of class III bacteriocins ﾿ 22

2.9 ﾿ Bacterial Resistance to Bacteriocins ﾿ 22

2.10 ﾿ Bacterial Pathogens Associated with Fruit Contamination ﾿ 22

2.10.1 ﾿ Campylobacter ﾿ 20

2.10.2 ﾿ Pathogenic Escherichia coli ﾿ 23

2.10.3 ﾿ Salmonella spp ﾿ 23

2.10.4 ﾿ Shigella spp ﾿ 24

2.10.5 ﾿ Staphylococcus ﾿ 25

2.10.6 ﾿ Vibrio ﾿ 25

2.10.7 ﾿ Listeria monocytogenes ﾿ 26

2.10.8 ﾿ Sporeformers ﾿ 26

2.11 ﾿ Sources of Contamination ﾿ 27

2.11.1 ﾿ Production Environment ﾿ 27

2.11.2 ﾿ Postharvest Handling ﾿ 28

2.11.3 ﾿ Human Hygiene ﾿ 29

2.12 ﾿ Pathogen Prevention ﾿ 30

2.12.1 ﾿ Processing Strategies ﾿ 30

2.12.2 ﾿ Handling Parameters ﾿ 32

2.12.3 ﾿ Alternative Technologies ﾿ 33

CHAPTER THREE

3.0 ﾿ Materials and Methods ﾿ 35

3.1 ﾿ Source of Materials ﾿ 35

3.2 ﾿ Sample Preparation ﾿ 35

3.3 ﾿ Isolation of Bacteria ﾿ 35

3.4 ﾿ Characterization of Isolates ﾿ 36

3.4.1 ﾿ Characterization of Bacteria Isolates ﾿ 36

3.4.2 ﾿ Microscopic Features ﾿ 36

3.5 ﾿ Identification of Isolates ﾿ 36

3.5.1 ﾿ Gram Staining ﾿ 37

3.5.2 ﾿ Biochemical Reaction Tests ﾿ 37

3.5.2.1 ﾿ Sugar Utilization Tests ﾿ 38

3.5.2.2 ﾿ Catalase Test ﾿ 38

3.5.2.3 ﾿ Indole Test ﾿ 38

3.5.2.4 ﾿ Citrate Utilization Test ﾿ 38

3.5.2.5 ﾿ Hydrogen Sulphide (H2S) Production Test ﾿ 39

3.5.2.6 ﾿ Voges-Proskauer Test ﾿ 39

3.5.2.7 ﾿ Urease Test ﾿ 39

3.5.2.8 ﾿ Methyl Red Test ﾿ 39

3.5.2.9 ﾿ Oxidase Test ﾿ 40

CHAPTER FOUR

4.0 ﾿ Results ﾿ 41

CHAPTER FIVE

5.0 ﾿ Discussion, Conclusion and Recommendations ﾿ 47

5.1 ﾿ Discussion ﾿ 47

5.2 ﾿ Conclusion ﾿ 49

5.3 ﾿ Recommendations ﾿ 50

﾿ References