Sampling
Known sample volumes were withdrawn fromthe fermentors, and one fraction was stored at −20 °C for subsequent analysis of extracellular metabolites. For quantification of cell mass, a known sample volume was treated with 2N HCl in order to solubilize undissolved CaCO3. The treated broth was centrifuged, and the pellet was washed once. After that, the wet biomass pellet was redissolved in distilled water and poured onto a preweight aluminum dish. Aluminum dishes were kept at 90 °C for 24 h in order to evaporate the water and subsequently stored in a desiccator until weighing.