ISOLATION AND SCREENING OF EXOPOLYSACCHARIDE PRODUCING LACTIC ACID BACTERIA ISOLATED FROM UGBA (PENTACLETHRA MACROPHYLA)

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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