EVALUATION OF ANTIMICROBIAL ACTIVITIES OF MICROORGANISMS ISOLATED FROM FERMENTED OGI

ABSTRACT

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Ogi is a popular fermented cereal gruel consumed mainly in the western part of Nigeria. Traditionally, ogi is normally administered to diarrhea patients to reduce the frequency of stooling. This study was undertaken to isolate, identify and determine the antimicrobial properties of Lactic Acid Bacteria (LAB) from fermented ogi. The antimicrobial activity of the cell free supernatant and the viable cells of the isolated LAB against food pathogen (Escherichia coli, Salmonella sp, Staphylococcus aureus, and Pseudomonas sp) were evaluated in this study using agar well diffusion assay. The organisms isolated were klebsiella sp, Escherichia coli, Streptococcus sp, Lactobacillus plantarum, Lactobacillus brevis and Enterobacter sp from fermented ogi in this study. Large zone of inhibition with cell free supernatant was observed against Salmonella species, Staphylococcus aureus, and pseudomonas species. This work has been able to show that the growth inhibition mediated by the fermented ogi on the test organisms is attributable to the presence of bioactive metabolites such as organic acid, hydrogen peroxide and bacteriocin produced by Lactic Acid Bacteria (LAB) present in the fermented ogi. However, ogi constitute a high antimicrobial properties against pathogenic microorganisms.

TABLE OF CONTENTS

Title page                                                                                                            i

Certification                                                                                                       ii

Dedication                                                                                                           iii

Acknowledgements                                                                                            iv

Table of contents                                                                                                v

List of tables                                                                                                       ix

List of figures                                                                                                     x

Abstract                                                                                                               xi

CHAPTER ONE

1.0      Introduction                                                                                          1

1.2       Aims and Objectives                                                                                                  4

CHAPTER TWO

LITERATURE REVIEW

2.1       Ogi Overview, preparation and fermentation                                                            5

2.2.      Microbiology of cereal and millet fermentation                                                        8

2.2.1.   Lab in cereal and millet fermentation                                                                       8

2.2.2    Commercial production of ogi                                                                                   10

2.3       Lactic acid bacteria (Lab)                                                                                           13

2.3.1    History and occurrence of lab                                                                                    14

2.3.2    Metabolic activities of lactic acid bacteria                                                                 15

2.3.2.1  Carbohydrate metabolism                                                                                         15

2.3.2.2  Protein metabolism                                                                                                    16

2.3.2.3 Lipid metabolism                                                                                                      18

2.3.3    Health benefit of lactic acid bacteria                                                                          18

2.3.4    Technological bi-products of lactic acid bacteria;                                                      22      

2.3.5    Properties of lactic acid bacteria                                                                                24

2.3.5.1 Preservative property of lactic acid bacteria                                                              24

2.3.5.1.1 Acid production                                                                                                       25

2.3.5.1.2 Exopolysaccharide formation                                                                                  26

2.3.5.1.3 Bacteriocins Production                                                                                          26

2.4       Bacteriocins of lactic acid bacteria                                                                             28

2.5       Bacteriocin application and prospect                                                                          28

2.6       Food spoilage microorganisms                                                                                    30                                                                                            

CHAPTER THREE

3.0       Materials and methods                                                                                                 31

3.1       Study area                                                                                                                    31

3.2      Sample collection                                                                                                         31           

3.3      Sterilization of materials                                                                                             31           

3.4      Normal saline preparation                                                                                           32           

3.5      Media preparation for isolation of lactic acid bacteria.                                              32            

3.6      Microbiological analysis                                                                                             32          

3.7       Identification of isolates                                                                                            33          

3.8       Gram staining                                                                                                            33           

3.9       Motility test (hanging drop method)                                                                          33

3.10       Biochemical tests                                                                                                          34

3.10.1    Catalase test                                                                                                           34                

3.10.2    Coagulase test (slide test)                                                                                           34

3.10.3    Oxidase test                                                                                                           34                 

3.10.4    Citrate utilization test                                                                                            35           

3.10.5    Indole test                                                                                                           35

3.10.6   Voges-proskauer test                                                                                            36

3.10.7   Methyl red test                                                                                                           36

3.10.8   Sugar utilization test                                                                                            36

3.10.9   Lactophenol Cotton blue staining                                                                                  37

3.11    Food pathogen indicator bacterial                                                                               37

3.12    Screening of lactic acid bacteria for antibacterial activity                                          37

3.12.1 Antibacterial activity of the isolated lactic acid bacteria                                            37

3.12.2 Agar well diffusion method                                                                                         38

 CHAPTER FOUR

4.0     Results                                                                                                                          39

CHAPTER 5

5.1     Discussion                                                                                                                     46       

5.2     Conclusion                                                                                                                    48

5.3     Recommendation                                                                                                          49                                                                                                                   

          References                                                                                                                    50                                                                                                                               

LIST OF TABLES

  TABLES     TITLES                                                             PAGES

          1               Total viable microbial count of fermented ogi sample                                       40

          2               Identification and Characterization of Isolate from Fermented

                           Ogi Samples                                                                                                  41

          3               Identification and characterize of Fungal Isolates                                         42

          4               Percentages occurrence of isolates from Fermented Ogi sample               43

          5               Identification and Characterization of Indicator Bacterial                                       44

          6               Antimicrobial activity of Lactic Acid Bacterial (LAB) isolates against

                           Isolates of the spoilage organisms                                                                 45

LIST OF FIGURES

FIGURES         TITLES                                                          PAGES

     1                          Flow chart of modification for ogi production process

                                 for corn starch production.                                                                    12

     2                          Uses and functional ingredients of lab                                                  23

CHAPTER ONE

1.0   INTRODUCTION

Ogi is an acid fermented cereal gruel made from maize (zeaymayz), sorghum (Sorghum vulgare), and millet (Pennisetum americanum) in West Africa which belong to different genera with different structure and chemical composition (Ohenhen et al., 2007). Fermentation has been used as a means of improving the keeping quality of food. It inhibits spoilage and pathogenic microorganisms by a combination of factors, which include production of organic acid, hydrogen peroxide and antibiotic- like substances (Nwachukwu et al., 2010).  In south-western Nigeria, raw ogi is normally administered to people suffering from gastroenteritis to reduce or minimize discomfort, lactic acid bacteria have been associated with the fermentation of ogi and have been frequently isolated (Ayorinde et al., 2017).

Ogi is a staple cereal fermentation product found predominantly in Southern and western Nigeria and is usually the first native food given to babies at weaning. It is produced generally by soaking maize grains in warm water for 2-3 days followed by wet milling and sieving through a screen mesh. Nnanyelugo and Onofiok (2004) reported the use of Ogi as a weaning food in western Nigeria to supplement breastfeeding between ages of 3-6 months. However; this may be inadequate to meet the nutritional demands of growing infants (Nnanyelugo and Onofiok, 2004).

Traditionally, ogi can be preserved by the continual changing of water. Ogi can also be preserved by refrigeration (Obi, 2014). Locally, in some communities, uncooked ogi is normally administered to people having running stomach (diarrhea) to reduce the frequency of stooling (Obi, 2014). Diarrhea is a serious health problem especially in children which often result to death in infancy (Adebolu et al., 2012; Wendell et al., 2008). Although diarrhea is self-limiting, but when it is as a result of bacterial infections, antibiotics therapy may be required. In searching for alternative to conventional antibiotics in treating bacterial causing diarrhea due to the fact that most bacteria causing infections have developed resistance to most of the conventional antibiotics, Adebolu et al (2012) observed that the liquor of uncooked ogi, a Nigerian fermented food has antimicrobial activity against common bacteria that cause diarrhea and antifungal properties as well (Adebayo and Aderiye, 2010). It is a popular breakfast cereal and infant weaning food in Nigeria (Aworh, 2008). It can be diluted into solids content of 8 to 10% and boiled into a pap, or cooked and turned into a stiff gel called "agidi" or "eko" before consumption (Bolaji et al., 2015).This same product is often eaten along with meat, stew, vegetable soup, steamed bean cake (‘moi-moi’) or fried bean cake (Akara). Moreover, Adebolu (2012) observed that the fermentation duration of uncooked ogi plays a significant role in the growth inhibitory activity of the liquor on susceptible organisms. Some of the pathogens that cause this condition include; Escherichia coli, Salmonella species, Shigella species, Staphylococcus aureus, Clostridium difficile and Campylobacter jejuni (Obi, 2014). Fermented ogi is also found to have some antimicrobial effect on Candida albicans which result to a fungal infection called candidiasis. Candida species are found everywhere and represent the most common fungal species that affects humans (Oluwafemi et al., 2011). Candidiasis can be characterized by symptoms such as constipation, diarrhea, and abdominal pain and itching.

The economic strength of the consumers does influence the choice of the supplements (Teniola and Odunfa, 2001). It has been established that substantial nutrient losses occur during the various stages of production of Ogi. These losses have been evaluated and reported by several workers (Bolaji et al., 2015). A lot of modification has also been introduced into the process as shown in various studies (Tables 1, 2, 3, 4, 5 and 6). Onyekwere et al. (1989) gave a description of the traditional as well as the industrial production of Ogi. Various supplements of Ogi have been developed including: tempeh, soybeans, pawpaw and cowpea. Olukoya et al. (1994) reported the development of an Ogi product (dogik), which have therapeutic properties on the basis of it stability to control diarrhea among infants. Dehydration of Ogi by drum or tray drying was reported to prolong shelf-life of Ogi   (Bolaji et al., 2015)

However, these dehydration methods were found to destroy heat-sensitive nutrients. According to Aworh (2008), the capacity to preserve food is directly related to the level of technological development. The author also stressed that slow pace of upgrading traditional food processing and preservation techniques in West Africa contributes to food and nutrition insecurity in the sub-region. An appropriate transformation of these primitive techniques to modern or mechanized stand the chance of creating employment opportunities in the rural areas, reduce rural-urban migration and the associated social problems (Aworh, 2008). The same author also highlighted that the adoption of inappropriate technologies in food processing, poor management, inadequate working capital and limited access to funds and financial institution are limiting the required growth of small scale food industries in West African countries. The traditional processing of Ogi often employ fermentation techniques that are characterized by the use of simple non-sterile equipment, introduction of natural inoculums, unregulated conditions, sensory fluctuations, poor durability and unattractive packing of the processed products which result in unpredictable quality of the product (Olanrewaju et al., 2009; Oyewole and Isah2012). According to Agarry et al. (2010), with increasing industrialization and urbanization, efforts are presently geared towards the development of large-scale factory production facilities for these foods where the quality of the finished product will be assured. Ogi contains lactic acid bacteria that produce nisin which have been found to have antimicrobial activity against several organisms (Oluwafemi, 2011).

Lactic acid bacteria (LAB) are gram positive bacteria that produce acid as a major end product of their fermentative metabolism (Oluwafemi and Adetunji. 2011). Lactobacilli are often present in decomposing plant material, milk and other dairy products and are important in production of fermented foods (Hidalgo & Vazquez, 2005). Lactic acid bacteria produce antimicrobial compound that enable them have competitive advantage over other microorganisms. Lactic acid bacteria are often recommended to replenish the population of friendly microorganisms which has been emptied out due to oral antibiotics and supplementation has been suggested to prevent fungi infection.

1.2 Aims and Objectives

The aim of this research work was to isolate and identify Lactic Acid Bacteria, from fermented ogi that are able to produce antibiotics, and check for their antimicrobial activities against some isolates from food pathogens.

Objectives:

1.     To identify and isolate LAB from fermented ogi.

2.     To check for antibiotic production

3.     To evaluate the activities of the antimicrobials produced on selected isolates from food     pathogens.

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