Liofilchem® ONPG 1.5% Supplement, 10mL x 10 Vials

Liofilchem® ONPG Supplement is a lyophilized additive designed for the determination of β-galactosidase enzyme activity in bacterial isolates. The supplement is incorporated into general-purpose microbiological media to enable differentiation based on the ability of microorganisms to hydrolyze ortho-nitrophenyl-β-D-galactopyranoside (ONPG).

This product is widely used in microbiology laboratories to support the identification and differentiation of Gram-negative bacteria, particularly within Enterobacteriaceae.

The supplement is added to media at a final concentration of 3 g per liter, as specified by the manufacturer

Principle of the Method

ONPG (ortho-nitrophenyl-β-D-galactopyranoside) is a chromogenic substrate for β-galactosidase.

When microorganisms produce β-galactosidase:

• ONPG is hydrolyzed.
• The reaction releases o-nitrophenol, a yellow compound.
• Yellow coloration indicates enzyme activity.

Unlike lactose, ONPG does not require permease for entry into the bacterial cell, allowing detection of β-galactosidase even in late lactose-fermenting organisms.

Composition

Each vial contains:

• Nitrophenyl-β-D-galactopyranoside – 15 mg 

Kit Contents

• 10 lyophilized vials of ONPG Supplement 

Product Code: 81032

Packaging: 10 vials (for use with 5 mL medium per vial)

Instructions for Use (Summary)

1. Reconstitute one vial aseptically with 1 mL sterile distilled water.
2. Mix until complete dissolution.
3. Add aseptically to 5 mL of general-use medium, previously autoclaved and cooled to 50°C.
4. Mix thoroughly and distribute into final containers. 

Applications

• Detection of β-galactosidase activity
• Differentiation of lactose fermenters and non-fermenters
• Identification of Enterobacteriaceae
• Supplementation of general-purpose culture media
• Clinical and research microbiology laboratories

Storage and Shelf Life

• Store at 5–12°C 
  81032_PI
• Shelf life: 3 years
  
  

Liofilchem ONPG Supplement (Code 81032) provides a reliable and standardized method for incorporating ONPG into general culture media for β-galactosidase detection. Supplied in stable lyophilized vials, it enables clear chromogenic differentiation of lactose-fermenting and late lactose-fermenting bacteria, supporting accurate microbial identification in clinical and laboratory settings.