ABSTRACT
[
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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