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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