ABSTRACT

The effect of carbon sources on the growth of antimicrobial producing Bacillus species in Citrullus vulgaris (Ogiri) was studied in this research. A total of 11 antimicrobial producing strains were isolated of which 8 were identified through morphological and biochemical tests were of the genus Bacillus. The isolates were identified as B. subtilis, B. megaterium and B. firmus. Isolate K6 identified as B. subtilis produced the highest recorded zone of inhibition (22 mm) when all the isolates were grown in culture media seeded with the test organism S. aureus. The effect of different carbon sources (glucose, starch and sucrose) on the Bacillus isolates were investigated individually. It was observed that optimum growth was achieved when all the Bacillus isolates were grown on media having starch (5 and 10% concentration) and sucrose (5 and 10% concentration) respectively. Weak to moderate growths were observed in the presence of glucose with evident growth seen more at 10% concentration and as such was deduced to be less effective for growth of the Bacillus species isolated from Citrullus vulgaris. Although all isolates grew well in the presence of starch, isolates K2 and K5 identified as B. megaterium were not able to grow with starch as a carbon source but could grow in the presence of glucose and sucrose. This could be attributed to their inability to hydrolyze starch. Isolates K1. K3, K4, K6, K7 and K8 could all grow in the presence of all the tested carbon sources. From the experiment, it was observed that maximum growth was with starch and sucrose for 72 hours at 37oC.  

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgments iv

Table of contents v

List of tables viii

Abstract ix

CHAPTER ONE

INTRODUCTION 1

1.1 Aim of the Study 3

1.2. Objectives of the Study 3

CHAPTER TWO

LITERATURE REVIEW 4

2.1 Fermentation 4

2.1.1 Importance of Fermentation 5

2.2 Fermented Foods 7

2.3 Traditionally Fermented Foods in Nigeria 8

2.4 Citrullus vulgaris (Melon) 11

2.4.1 Description of the Seeds 11

2.4.2 Composition of the Seeds 11

2.4.3 Importance of Citrullus vulgaris 11

2.5 Ogiri 12

2.5.1 Production of Ogiri 12

2.5.2 Microbiology of Ogiri 13

2.6 Bacillaceae 14

2.6.1 History of Genus Bacillus 14

2.6.2 Genus Bacillus 15

2.6.3 Bacillus as a Source of Antimicrobial Compounds 17

2.6.3.1 Ribosomal Peptide Antibiotics  18

2.6.3.2 Non-ribosomal Peptide Antibiotics  19

2.7 Effect of Different Carbon Sources on the Growth of Antimicrobial Producing Microorganisms 21

CHAPTER THREE

MATERIALS AND METHODS 22

3.1 Sample Collection 22

3.2 Isolation of Antimicrobial Producing Organisms from Ogiri Samples 22

3.3 Characterization and Identification of Antibiotic Producing Bacilli from Ogiri 23

3.3.1 Biochemical Analysis of the Isolates 23

3.3.1.1 Gram Staining 23

3.3.1.2 Catalase Test 24

3.3.1.3 Spore Formation Test 24

3.3.1.4 Methyl Red Vogues Proskauer (MR-VP) Test 25

3.4.1.5 Oxidase Test 26

3.4.1.7 Citrate Test 26

3.4.1.8 Starch Hydrolysis Test 26

3.4.1.9 Carbohydrate Fermentation Test 27

3.5 Effect of Different Carbon Sources on the Growth of Antimicrobial Producing Bacillus Species 27

CHAPTER FOUR

RESULTS 28

CHAPTER FIVE

DISCUSSION AND CONCLUSION 32

5.1 Discussion 32

5.2 Conclusion 32

References 35