1. 47-mm glass fiber paper filters (Whatman GF/C, Schleicher & Schuell Co.) were presaturated with 100 ml distilled water and dried overnight at 60°C and 1h at 120°C, to evaporate all the water. Eppendorf tube containing a presaturated paper filter were pre- weighted.
2. Replicate aliquots (10 ml) of culture suspensions were centrifuged (4700xg, 10 min, room temperature).
3. washed with 80 ml 0.5 M ammonium formate to remove the salt content and resuspended in 0.5 M ammonium formate.
4. After OD750 determination a defined volume of culture was filtered (with a vacuum pump) through the pre-weighed glass fiber paper filter.
5. The filters with cells were then lyophilized for 24 h to volatilize the ammonium formate and the water.
6. After cooling to room temperature in a desiccator, the filters were weighted to determine the relative dry biomass.