A rapid method for the determination of microbial biomass by dry weight using a moisture analyser with an infrared heating source and an analytical balance.

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 r(2) of 0.99. The recovery of an internal standard ranged between 94.2 and 106.4% with a precision of 1.39-4.53%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.