Methods for the quantification of Frankia cell biomass

Six methods for the estimation of microbial biomass were compared for determination of Frankia cell concentrations. Six strains of Frankia were cultivated in stationary culture, harvested by centrifugation, washed with a saline buffer and diluted to five standardized concentrations. These cell suspensions were then used to assess reliability of each of the biomass determination methods. The destructive total protein determination methods were the most sensitive and reliable. Two non-destructive methods, packed cell volume and turbidity measurement, were also accurate, and because of their simplicity hold advantage for routine growth measurements and inoculum dilutions. Dry weight determinations were inconsistent for the small cell masses used in this study. An ELISA procedure demonstrated reliability but little sensitivity.