Lactose Bile Salt Medium for Fecal Coliform Determination in Cosmetics
This selective liquid medium is designed for the detection and enumeration of fecal coliforms in cosmetic samples. It adopts bovine bile salt as selective inhibitor and bromocresol purple as pH indicator to identify lactose-fermenting fecal coliforms.
Formula Composition (per Liter)
| Ingredient |
Content |
| Peptone |
20.0 g |
| Lactose |
5.0 g |
| Bovine bile salt |
5.0 g |
| Bromocresol purple |
0.01 g |
| Final pH |
7.4 ± 0.1 at 25 ℃ |
Verification Principle
Peptone supplies carbon and nitrogen sources to support bacterial growth. Bovine bile salts suppress the growth of Gram-positive bacteria. Lactose is the fermentable carbohydrate for coliform group. Bromocresol purple acts as a pH indicator, turning yellow under acidic conditions and purple under alkaline conditions.
Directions for Use
Weigh 30.0 g of the medium powder, heat and dissolve in 1000 mL distilled water, dispense into containers, autoclave at 115 ℃ for 20 minutes, and reserve for later use.
Microbial Performance Test for Lactose Bile Salt Medium
Prepare the medium following the instructions. Inoculate the quality control strain and incubate aerobically at 44 ± 0.5 ℃ for 24–48 hours.
