Elemental analysis for biomass determination in the presence of insoluble substrates

Growth determination in the presence of solid substrates presents a unique set of experimental difficulties which limit the utility of most commonly used techniques for biomass measurement. In an effort to develop a method for routine growth determination in the presence of elemental sulfur and other insoluble substrates, we evaluated an approach by which the cell carbon of bacteria collected on glass-fiber filters was measured directly with a Carlo Erba elemental analyzer. Even in the presence of large excesses of elemental sulfur, iron and manganese oxides or smectite clays, cell carbon measurement proved effective with a sensitivity at least equal to that of spectrophotometric optical density determination. Sample preparation was rapid and required no costly materials. The results obtained here indicate that this approach is well suited for bacterial growth detection in the presence of inorganic solid substrates.