ABSTRACT
Exopolysaccharides
are high molecular weight polymers that are composed of sugar residues and are
secreted by microorganisms into the surrounding. This work is aimed at
isolating and screening of exopolysacchride producing lactic acid bacteria
(LAB) isolated from Ugba (Pentaclethramacrophylla).
Locally produced samples of Ugba were gotten from an open market in Ekwulobia,
Anambra State, Nigeria. The samples were plated on M17 agar, MRS (de Man Rogosa
and Sharp) agar and on Nutrient Agar. A total of 25 presumptive LAB isolates
were gotten after some physiological, morphological and biochemical test were
carried out. 8 isolates (EXO1, EXO2, EXO3, EXO4, EXO5, EXO6, EXO7, EXO8) showed
exopolyaccharide activity which was confirmed by the determination of their
ropy and mucoid characteristics which was done using different sugar
supplements as carbon sources. The length of strand (ropiness) formed by ropy
strains plated on M17, MRS and NA supplemented with sucrose, lactose and
glucose as carbon sources were calculated and recorded, while (EXO1, EXO2,
EXO3, EXO6, and EXO8) strains plated on MRS and M17 agar showed better mucoid
activity. This shows that the length of the strands exhibited by the ropy and
mucoid isolates of LAB varied according to strain and carbon source.
TABLE
OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgment iv
Table of contents v
List of tables vi
Abstract
CHAPTER
1: INTRODUCTION
1.1 Background of the Study
1.2 Aim
and Objective:
1.2.1 Objectives:
CHAPTER
2: LITERATURE REVIEW
2.1 Definition
of Fermentation:
2.1.1 Classification of fermented foods
2.1.2 Benefits of fermenting food
2.2 Microflora in fermented foods
2.3 Ugba
2.3.1
Ugba Fermentation
2.3.2 Preparation
of ugba;
2.4 Lactic
acid bacteria.
2.4.1 History
and occurrence of lab
2.4.2 Health
Benefit of lactic acid bacteria
2.4.3 Technological
Bi-Products of Lactic Acid Bacteria;
2.5 Exopolysaccharide:
2.5.1 Definition
and classification of Exopolysaccharides:
2.5.2 Applications
of Exopolysaccharides in the industry
2.5.3 Potential
health benefits of Exopolysaccharides
2.5.4 Factors
limiting the use of Exopolysaccharides
CHAPTER
3: MATERIALS AND METHOD
3.1 Study
Area
3.2 Collection
of Samples
3.3 Culture
Media Preparation and Sterilization
3.5 Preparation
of homogenate ugba samples
3.5 Inoculation
of samples
3.6 Colony
count of isolates
3.7 Characterization
and identification of isolates
3.7.1 Isolation
and identification of lactic acid bacteria
3.7.2 Phenotypic characterization
3.8 Biochemical characterization
3.8.1 Gram Staining
3.8.2 Catalase
Test
3.8.3 Citrate Test
3.8.4 Motility, Indole, Urease Test (MIU).
3.8.5 Oxidase Test
3.9 Characterization of lactic acid bacteria
3.9.1 Growth at different temperatures
3.9.3 Gas Production from glucose:
3.9.4 Carbohydrate Fermentation Test:
3.10 Detection
of exopolysaccharide
3.10.1 Visual
Appearance:
Chapter 4 Results
Chapter 5
5.1
Discussion
5.2
Conclusion and Recommendation
References
LIST OF TABLES
TABLES PAGE
Table 3. The Benefits of Food Fermentation
Table 1. Different Classification of Fermented
Foods.
Table 2. Other
Classifications of Fermented Foods.
Table 4 Total
Colony Forming Unit
Table 5: Morphological,
Physiological and Biochemical Characteristics
of
Isolated Genera of Lab
Table 6: Mucoidy
Character of EPS in Different Agar Media With Lab Strains
Table 7: Measurement
of Ropiness Of ESP In Different Agar Supplemented
With Glucose Containing
Lab Strains
Table 8: Measurement Of Ropiness Of EPS In
Different Agar Supplemented
With Sucrose Containing Lab Strains
CHAPTER
1
INTRODUCTION
1.1 Background of the study
Lactic acid bacteria (LAB) are Gram-positive
microorganisms that play an essential role in the industrial production of
fermented dairy products. The metabolic products they generate during
fermentation and ripening confer the rheological and organoleptic qualities desired
by these products (Bennama et al.,
2012). Some strains are known to produce exopolysaccharide (EPS), which play an
important role in the development of the texture of yoghurt and other fermented
milks, cheeses and low fat dairy desserts (Hassan, 2008). EPS from LAB are
divided into two groups, homo- and hetero-EPS. Homo-EPS are composed of one
type monosaccharide, whereas hetero-EPS consist of regular repeating units of
3-8 different carbohydrate molecules. EPS imparts highly desirable rheological
changes in the food matrix such as increased viscosity, improved texture and
reduced syneresis (Badel et al.,
2011). Incorporation of EPS or EPS-producing starters in dairy foods can
provide viscosifying, stabilizing, and water-binding functions. In situ
production of EPS is very important in the manufacture of fermented dairy
products, such as yogurt, drinking yogurt, cheese, cultured cream and
milk-based desserts. EPSproducing LAB has a greater ability to withstand
technological stresses (Stack et al., 2010) and survive the passage through the
gastrointestinal tract compared to their non-producing bacteria. In recent
times, EPS produced by LAB have received mounting attention; mainly because of
their health benefits. EPSs have been proved to show important health benefits
like antioxidant, cholesterol lowering, antitumor, antiviral, and
immunomodulatory activities (Madhuri and Prabhakar, 2014). Also, they reduce
formation of pathogenic biofilms, help in modulation of adhesion to epithelial
cells and increase levels of bifidobacteria showing a prebiotic potential
(Hongpattarakere et al., 2012).
Hence, the choice of EPS- producing starter cultures seems to give several
advantages over non- producing ones. Also, LAB possess generally regarded as
safe (GRAS) status which allows them to be incorporated in food without
labeling. Most of the EPS producing LAB can be isolated from different
fermented foods such as dahi, lassi, yoghurt, cultured buttermilk, cheeses,
yoghurt, kefir, and other fermented dairy products (Bunkoed and Thaniyavarn,
2014). Furthermore, EPS producing strains can be also found in other
environments such as gut of different animals and humans. Selection for LAB
strains with newer properties can be used as new, functional starter cultures
may lead to improved fermentation process and an enhanced quality of the end
product. As information regarding isolation of EPS producing cultures from
dairy products in Indian condition is scanty.
1.2 AIM AND OBJECTIVE:
To isolate and screen exopolysaccharide
producing lactic acid bacteria from Ugba (Pentaclethra
macrophyla)
1.2.1 OBJECTIVES:
1. To
isolate exopolysaccharide producing lactic acid bacteria
2. Screening
of exopolysaccharide producing lactic acid bacteria for the determination of
its ropy and mucoid characteristics
3. To
check for the application of exopolysaccharide producing lactic acid bacteria
isolated from Pentaclethra macrophylain
in the production of other fermented products.
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