Screening for Lactobacilli in Dairy Products

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Probiotics in Dairy Products

• Definition: Live microorganisms which when administered in adequate amounts confer a health benefit on the host".• Probiotics are commonly consumed as part of fermented

foods with specially added active live cultures, such as in yoghurt, or as dietary supplements

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Probiotics: Lactic Acid Bacteria

• `Lactic acid bacteria’ includes species of the following genera: • Lactobacillus • Streptococcus• Enterococcus• Pediococcus• Leuconostoc

All these species can produce lactic acid in considerable amounts.• They are Gram-positive, cocci or rods, catalase and oxidase

negative

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Detection of Lactobacillus in Yoghurt by Simple Staining Procedure•The MRS formulation was developed by de Man,

Rogosa and Sharpe1 to encourage the growth of the `lactic acid bacteria’ •Selectivity of MRS media can be altered by pH

adjustment. • Lactobacilli will tolerate lower pH levels (pH 5.0-6.5) with

pediococci and leuconostocs growing best within this range than streptococci.

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Detection of Lactobacillus in Yoghurt by Simple Staining Procedure• Lactobacilli are microaerophilic and require incubation at

30⁰C for 5 days or 35⁰C for 3 days. • Colonies may be compact or feathery, and are small, opaque

and white.• Perform simple stain and catalase test on the isolated

colonies

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Screening for some Protease-containing Drugs

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Protease activity in alpha-chymotrypsin ampoule, iruxol ointment and digestin syrup• Alpha-Chymotrypsin contains a special type of proteases

called “endopeptidases”.• Chymotrypsin cleaves peptide bonds formed by aromatic

residues such as tyrosine, phenylalanine and tryptophan.• Iruxol ointment contains a collagenase clostridiopeptidase

and other proteases.• Digestin syrup has papain, pepsin and sanzyme.

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Add alpha chymotrypsin to the first cup

Add iruxol ointment to the

second cup

Add digestin syrup to the third

cup

Skimmed Milk Agar Plate

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The clear zones surrounding the cups are indicative of the proteolytic activity of

the preparations

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