GASTROINTESTINAL TRACT

A1.0  Biologically important functions of Large Intestine

·       Absorption and secretion of certain electrolytes, like water.

·       Storage and excretion of waste materials.  

A2.0  Composition and activities of gut microflora           

Human Body:

·       Eukaryotic cells ≈10¹³

·       Prokaryotic cells ≈10¹⁴

≈50 genera with several hundred species of bacteria

         A3.0  Factors Affecting Bacterial activities  

• Substrate availability

• Redox potential

• pH

• O₂ tension

• Distribution in the colon

(Cummings et al, 1991)

A4.0  GUT MICROBIAL BALANCE

    (Rotimi,1981)

          A5.0  FACTORS AFFECTING GUT MICROBIAL BALANCE

             ·       Abusive & improper dietary habits

·       Starvation

·       Alcohol consumption

·       Stress

·       Diseases of the Intestinal Tract

·       Oral antibiotic therapy

·       Surgical operation

(Wang,1993)

A6.0  COMPOSITION AND HEALTH EFFECTS OF PREDOMINANT HUMAN FECAL BACTERIA

A7.0  Substrates for Colonic bacterial growth  

·           Resistant Starch                   

·       Polysaccharides

·       Unabsorbed Sugars- lactose, raffinose, stachyose

·       Oligosaccharides- fructooligosaccharides, oligofructose, inulin

·       Dietary & endogenous proteins (e.g. pancreatic enzymes)

·       Sugar Alcohols – sorbitol, xylitol

·       Endogenous Carbohydrates – glycoproteins (e.g. mucin)

·       Other Food Additives

A8.0  Major Typ es of Metabolic Reaction

    ·           Synthesis of vitamins and amino acids.

·       Degradation of starches to simple sugars.

·       Fermentation of non-starch polysaccharides to volatile fatty acids.

·       Degradation of proteins to amino acids, amines & ammonia.

·       Hydrogenation of unsaturated fatty acids.

·       Transformation of primary to secondary bile acids.

·       Transformation of cholesterol to other sterols.

·       Reduction of nitrate to nitrite.

·       Detoxification. e.g. bilirubin to urobilins.

·       Toxin production, e.g. glycolysis of cycasin.

·       Carcinogen formation, e.g. synthesis of N- nitroso compounds.  

A9.    Generalized scheme of fermentation by human colonic microflora

(Gibsan & Raberfroid,1994)

  “Organisms and substances which contribute to intestinal microbial balance”

(Sperti, 1971)

 “A live microbial feed suppliment which beneficially affects the host animal by improving its intestinal microbial balance.”

                          (Fuller, 1989)                 

B1.0  CRITERIA TO BE PROBIOTIC

1.     The probiotic must be capable of being prepared in a viable manner and on a large scale.

2.     During use and under storage the probiotic should remain viable and stable.

3.     It should be able to survive in the intestinal ecosystem.

4.     The host animal gain beneficially from harboring the probiotic.

B2.0  Composition of PROBIOTICS

Lactobacilli

Lactobacillus bulgaricus

Lactobacillus acidophilus

Lactobacillus casei

Lactobacillus helveticus

Lactobacillus lactis

Lactobacillus salivarius

Lactobacillus plantarum

Lactobacillus delbruekii

Streptococci

Streptococcus thermophilus

Streptococcus lactis

Enterococci

Enterococcus faecium

Enterococcs faecalis

Bifidobacteia

Bifidobacterium adolescentis

Bifidobacterium bifidum

Bifidobacterium infantis

Bifidobacterium longum

B3.    EXAMPLES OF FERMENTED MILK PRODUCTS

ANTAGONISTIC METABOLITES

ORGANIC ACIDS – Lactic acid , Acetic acid, Propionic acid

BROAD SPECTRUM ANTAGONISTS

HYDROGEN PEROXIDE (H₂O₂)

DIACETYL

BACTERIOCINS  

E1.1   ORGANIC ACIDS  

 

Lethality / toxicity

Organic acids > Inorganic acids

PA>AA>LA

E1.2   BRAOD SPECTRUM ANTAGONISTS  

General characteristics:  

·       Low molecular weight

·       Free of nitrogen

·       Acidic in nature

·       Resistant to proteolytic enzymes and heat

  LAB, associated with antagonism:  

ACIDOPHILIN, LACTOCIDIN, ACIDOLIN

Producer: Lactobacillus acidophilus

Effective against both Gram positives and Gram negatives

 

BULGARICAN

Producer: Lactobacillus delbruckii ssp.bulgaricus

Effective against Gram positives and Gram negatives  

 

BIFIDINE

Producer: Bifidobacterium bifidum

Characteristics:

• Heat stable, contains two amino acids: phenylalanine and glutamic acid.

• Effective against gram +ves and gram –ves.

  FOOD SPOILAGE AND FOOD BORN PATHOGENS 

Escherichia coli

Pseudomonas aeruginosa

Salmonella typhimurium

Bacillus fragilis

Bacillus cereus

Proteus vulgaris

Staphylococcus aureus

Clostridium perfringens

Shigella dysentriae  

E1.3   HYDROGEN PEROXIDE

  H₂O₂ producer LAB Species  

E1.4   DIACETYL  

Diacetyl producers  

Lactobacilli

Leuconostocs

Lactococcus lactis ssp. lactis biovar. diacetylactis

Propionibacteria

Effective Level  

Species                         effective concentration(µg/ml)

LAB                                                    >400

Gram –ves                                         ≤200

Gram +ve (non-lactic)                    >350  

Production level

       Leuconostocs                                     14 µg/ml

        Lactobacilli                                        84 µg/ml

Effectiveness of Diacetyl  

E1.5   BACTERIOCINS  

Anti-microbial peptides or small proteins active against bacteria closely related to the producer strain.

General Characteristics  

·       Producer strain is typically immune against its own bacteriocin.

·       Heat resistant, but are inactivated by proteolytic enzymes.

·       Bacteriocins having MW< 10 kD are small peptides, they include lantibiotic type      bacteriocins.

·       Bacteriocins have MW>30 kD are large proteins.

·       Another group of bacteriocins may be a complex molecule with a lipid or polysaccharide moiety, essentially required for its activity.

BACTERIOCIN PRODUCERS  

LACTIC ACID BACTERIA  

Lactococcus lactis

Lactobacillus

Leuconostoc

PROPIONIC ACID BACTERIA  

Prpionibacterium

E2.0   ANTICARCINOGENIC/ANTITUMOR ACTIVITIES  

CANCER: Set of diseases, in which uncontrolled growth of cells occur.

Types of Cancer Inhibited by Nutritional factors  

MECHANISM OF ANTITUMOUR EFFECT