Use of membrane filter technique in the microbiological control for the brewing industry.

A physical method was developed involving serial filtration with membrane filters for separating yeast cells from bacteria. Such a method eliminates the need for antibiotics previously required to permit differential counting of such populations. All yeast cells filtered were successfully retained and cultivated on a 1.2-mu membrane filter by use of a synthetic medium. All bacteria filtered avoided entrapment on a 1.2-mu membrane filter and were successfully retained and cultivated on a 0.22-mu membrane filter with the same synthetic medium. Final filtrates from these serial filtrations were free from all yeast cells and bacteria when tested with Fluid Thioglycollate Medium.