CHARACTERIZATION AND FUNCTIONAL POTENTIALS OF LACTIC ACID BACTERIA ISOLATED FROM FERMENTING TIGER NUT MILK

ABSTRACT

This study was aimed to characterize and determine the functional potentials of lactic acid bacteria isolated from fermenting tiger nut milk. The specific objectives were to isolate lactic acid bacteria from fermenting tiger nut milk, characterize and identify lactic acid bacteria using morphological, physiological and biochemical techniques and to ascertain the functional potentials of lactic acid bacteria isolated from fermenting tiger nut milk. The result of the analysis showed that tiger nuts are high in carbohydrate, fat and fibre content. . All the isolates were negative for Catalase test. Many isolates were negative for gas production from glucose and few isolates were positive. All the isolates indicated negative haemolytic test. The antimicrobial properties of the samples was determined by measuring the diameter of zone of inhibition, the maximum zone of inhibition was observed in case of (TMP2472) Lactobacillus pentosus with 14mm zone of inhibition while the minimum was observed in (TMP 051) Lactobacillus fermentum with 3mm zone of inhibition. It has been reported that lower temperature slows down chemical reactions, enzyme actions and microbial growth; it is therefore recommended that when tiger nut milk is not to be served immediately, it should be stored at low temperatures (i.e. in the refrigerator) so as to prevent the growth of spoilage organisms and maintain the quality of the milk.

TABLE OF CONTENTS 

Title page ﾿ i

Certification ﾿ ii

Dedication ﾿ iii

Acknowledgements ﾿ iv

Table of contents ﾿ v

List of tables ﾿ vii

List of figures ﾿ viii

Abstract ﾿ ix

CHAPTER ONE

1.0 ﾿ Introduction ﾿ 1

1.1 ﾿ Aim and Objectives ﾿ ﾿ 4

CHAPTER TWO

2.0 ﾿ Literature Review ﾿ 5

2.1 ﾿ Lactic Acid Bacteria (LAB) ﾿ 5

2.2 ﾿ Taxonomy of Lactic Acid Bacteria ﾿ 5

2.3 ﾿ Sources of Lactic Acid Bacteria ﾿ 6

2.4 ﾿ Classification of Lactic Acid Bacteria ﾿ 6

2.5 ﾿ Food fermentation ﾿ 7

2.6 ﾿ Benefits of Food Fermentation ﾿ 9

2.7 ﾿ Advantages of Food Fermentation ﾿ 10

2.8 ﾿ Importance of Lactic Acid Bacteria ﾿ 10

2.9 ﾿ Beneficial Role of Lactic Acid Bacteria ﾿ 11

2.10 ﾿ Importance of LAB and their Effect on Human Health ﾿ 12

2.11 ﾿ Lactic Acid Bacteria and Other Effects on the Immune System ﾿ 13

2.12 ﾿ Lactic acid fermentation ﾿ 14

2.13 ﾿ Importance of Tiger nuts ﾿ 15

CHAPTER THREE

3.0 ﾿ Materials and Methods ﾿ 19

3.1 ﾿ Sample Collection and Preparation ﾿ 19

3.1.1 ﾿ Tiger nut milk extraction ﾿ 19

3.1.2 ﾿ Glass wares and media preparation ﾿ 20

3.1.3 ﾿ pH determination ﾿ 20

3.2 ﾿ Proximate Analysis ﾿ 21

3.3 ﾿ Microbiological Analyses ﾿ 23

3.3.1 ﾿ Enumeration of total bacteria ﾿ 23

3.3.2   Enumeration of Coliform ﾿ 24

3.3.3 ﾿ Enumeration of Yeast ﾿ 25

3.3.4    Enumeration of Lactic acid bacteria ﾿ 25

3.3.5   Isolation of Lactic Acid Bacteria ﾿ 26

3.3.6. ﾿ Characterization of Lactic Acid Bacteria ﾿ 26

3.3.6.1 Morphological characterisation ﾿ 27

3.3.6.2 Biochemical characterization ﾿ 27

3.3.6.3 Physiological characterization ﾿ 29

3.3.7 ﾿ Identification of Lactic Acid Bacteria ﾿ 30

3.4 ﾿ Safety Properties of Lactic Acid Bacteria ﾿ 30

3.4.1 ﾿ Haemolytic test ﾿ 30

3.4.2 ﾿ Antibiotic resistance pattern    ﾿ 31

3.5    ﾿ Determination of Functional Potentials ﾿ 31

3.5.1   Tolerance to low pH 3.5 and 2.5 ﾿ 31

3.5.2   Tolerance to 0.3% Bile salt ﾿ 31

3.5.3   Antimicrobial properties ﾿ 32

CHAPTER FOUR

4.0 ﾿ Results ﾿ 34

CHAPTER FIVE

Discussion, Conclusion and Recommendations ﾿ 45

5.1 ﾿ Discussion ﾿ 45

5.2 ﾿ Conclusion ﾿ 46

5.3 ﾿ Recommendations ﾿ 47

References ﾿ 48

LIST OF TABLES

Table ﾿ Title ﾿ Page 

1: ﾿ Proximate Composition of Fermenting Tiger nut milk ﾿ 33

2: ﾿ pH and microbial load of tiger nut milk during fermentation ﾿ 34

3: ﾿ Morphological Characteristics of Lactic Acid Bacteria Isolated from Tiger 

nut milk ﾿ 36

4: ﾿ Biochemical and physiological characteristics of Lactic Acid Bacteria 

isolated from fermenting Tiger nut milk ﾿ 37

5: ﾿ Haemolytic activity of Lactic Acid Bacteria isolated from fermenting 

Tiger nut milk ﾿ 40

6: ﾿ Result for antibiotic sensitivity ﾿ 41

7: ﾿ Antimicrobial properties of lactic acid bacteria ﾿ 44

LIST OF FIGURES

Figure ﾿ Title ﾿ Page 

1: ﾿ Tiger nut milk extraction ﾿ 19

2: ﾿ Tolerance to low pH ﾿ 42

3: ﾿ Tolerance to 0.3% bile salt ﾿ 43