PROBIOTIC POTENTIAL OF LACTIC ACID BACTERIA ISOLATED FROM FISH FEEDS

ABSTRACT

Probiotics are the health promoting viable microorganisms that exhibit a beneficial effect on the health of human being by improving the intestinal microbial balance. Probiotic bacteria may produce various compounds, which are inhibitory to the growth of pathogen, which include organic acids (lactic and acetic acids), bacteriocins, and reuterin. In the present study a total of six(6) isolates of Lactic Acid Bacteria from fish feed were purified and screened for their antimicrobial activity against four human pathogenic organisms (Aspergillus niger, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa). The six(6) isolates were considered for their probiotic potential. The isolates were tolerant to 1, 3 and 6% NaCl, temperature of 25, 30, 37 and 400C. the isolates could able to survive at pH ranges 5-9. Some of the isolates were also resistant to antibiotics such as Amoxicillin, Ampicillin and Augumentin.  The selected lactic acid bacteria exhibited excellent probiotic characteristics and thus can be used as a potential source of probiotic. Study affirms their use in the development of new pharmaceutical preparations and functional foods as probiotics for the betterment of public health.

TABLE OF CONTENTS

Title Page                                                                                                                                i

Certification                                                                                                                           ii

Dedication                                                                                                                               iii

Acknowledgement                                                                                                                  iv

Table of Contents                                                                                                                   v

List Of Tables                                                                                                                         vii

Abstract                                                                                                                                   viii

CHAPTER ONE

1.0           Background of study                                                                                                   1

1.1           Aim of the study                                                                                                         2

1.2           Objectivs of the study                                                                                                 2

CHAPTER TWO

2.0       Literature Review                                                                                                       3

2.1       Lactic Acid Bacteria                                                                                                   3

2.2       Classification of lactic acid bacteria                                                                          3

2.3       Lactic acid bacteria as biopreservatives                                                                     4

2.4       Probiotics as immunity stimulators                                                                            6

2.5       Health benefits of probiotics                                                                                      7

CHAPTER THREE

3.0       Materials and methods                                                                                                12

3.1       Sample collection                                                                                                       12

3.2       Media preparation                                                                                                      12

3.3       Evaluation of probiotic potentials of isolated LAB cultures                                      12

3.3.1    NaCl tolerance                                                                                                            12

3.3.2    Temperature tolerance                                                                                                12

3.3.3    pH tolerance                                                                                                               13

3.3.4    Antibiotic resistance                                                                                                   13

3.3.5    Screening of isolated bacteria cultures for antimicrobial activity                                    13

CHAPTER FOUR

4.0       Results                                                                                                                       15

CHAPTER FIVE

5.0       Discussion and conclusion                                                                                         21

5.1       Discussion                                                                                                                   21

5.2       Conclusion                                                                                                                  22        References 

LIST OF TABLES

Table 1:           NaCl tolerance of LAB isolates                                 16

Table 2:           Temperature tolerance of LAB isolates                     17

Tale 3:             pH tolerance of LAB isolates                                     18

Table 4:           Antibiotic susceptibility profile (mm) of the isolates   19

Table 5:           Diameter zone of inhibition (mm) produced by the isolates against selected organisms      20                                           

CHAPTER ONE

1.0       BACKGROUND OF STUDY

The term probiotic is defined as “a live microbial feed supplement which beneficially affects the host animal by improving its microbial balance’’ (Aslam and Qazi, 2010). Probiotics are also defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (FAO/WHO, 2013), as updated by Hill et al. (Hill et al., 2014). Probiotic bacteria may produce various compounds, which are inhibitory to the pathogen’s growth, which include organic acids (lactic and acetic acids), bacteriocins, and reuterin. The organic acids not only lower the pH, thereby affecting the growth of the pathogen, but they can also be toxic to the microbes (Tambekar and Bhutada, 2010). The beneficial health effects claimed for probiotics are regulation of microbial balance in the gastrointestinal tract, reduction of serum cholesterol levels, alleviation of lactose intolerance symptoms, lowering the risk of colon cancer, enhancement of nutrients bioavailability, prevention or reduction of the prevalence of allergies in susceptible individuals, enhancement of the immune system, and improvement of calcium absorption (Argyri et al., 2013; Yoon et al. 2006). There is increasing evidence that probiotics are beneficial in gastrointestinal disturbances, such as diarrhoea, dysentery, typhoid, e.t.c. (Tambekar and Bhutada, 2010). It is important to underline when considering the effectiveness and biological activity of probiotics, prebiotics or their combination (synbiotics) that they are food products and not drugs.

Furthermore, in many cases, their effects are mainly prophylactic in nature, rather than therapeutic, i.e. preventive rather than curative (Suskovic et al., 2001). Lactic acid bacteria were referred to as probiotics in scientific literature by Lilley and Stillwell. Lactic acid bacteria (LAB) are a group of Gram positive, non-spore forming, cocci or rods which produce lactic acid as major end product from fermentation of carbohydrates. Majority of microorganisms used as probiotics belong to the LAB and bifidobacteria. Within the group of LAB, Lactobacillus species are most commonly utilized group of microorganisms for their potential beneficiary properties as probiotics. The antagonistic activity of such bacteria is known to inhibit a large number of enteric and urinary pathogenic bacteria (Hutt et al., 2006). Lactic acid bacteria including Lactobacillus, leuconostoc, Lactococcus, pediococcus and Bifidobacterium are found throughout the gastrointestinal tract. Lactobacillus and Bifidobacterium spp. are prominent members of the intestinal flora and are the commonly studied probiotics bacteria. They cause reduced lactose intolerance, alleviation of some diarrhoeas, lowered blood cholesterol, increased immune response and prevention of cancer. The selection criteria for probiotic LAB include: safety, viability/activity in delivery vehicles, resistance to acid and bile salt, adherence to gut epithelial tissue ability to colonise the gastro intestinal tract, production of antimicrobial substances, ability to stimulate a host immune response and the ability to influence metabolic activities such as vitamin production, cholesterol assimulation and lactose activity (Savodago et al., 2006). Therefore, LAB isolated from fish feed were evaluated for their potential as probiotics.

            1.1           AIM

The aim of the study is to evaluate the potential of Lactic Acid Bacteria isolated from fish feeds as probiotics

            1.2           OBJECTIVES OF THE STUDY

The study was carried out to determine the following:

v  pH tolerance of  Lactic Acid Bacteria (LAB).

v  Temperature, HCl and NaCl tolerance.

v  Antibiotic susceptibility pattern of selected LAB isolates.

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