Aims: Microbial biomass is an important biotechnological parameter. The
traditional method for its determination involves an oven-drying step and
equilibration to room temperature before weighing, and it is tedious and time
consuming. This work studied the utilisation of a moisture analyser consisting
of an efficient infrared-heating module and an analytical balance for the determination
of microbial biomass by dry weight.
Methods and Results: The method duration depended on the sample volume
and was between 7 and 40 min for sample volumes of 1–10 ml. The method
precision depended on the total dry weight analysed – 10 mg of total dry
weight being sufficient to achieve coefficients of variation of 5% or less. Comparison
with the conventional oven method provided a correlation coefficient
r2 of 0Æ99. The recovery of an internal standard ranged between 94Æ2 and
106Æ4% with a precision of 1Æ39–4Æ53%CV.
Conclusions: Validation revealed sufficient method accuracy, precision and
robustness and was successfully applied to the study of yeast and bacterial
growth kinetics. Techniques are discussed that allow for increased method precision
at low biomass concentrations, and equations are provided to estimate
required drying time and method precision based on sample volume and total
sample dry weight, respectively.
Significance and Impact of the Study: This work presents a rapid method for
the determination of microbial biomass, allowing for the timely implementation
of biomass-based information in biotechnological and laboratory
protocols.