Hi there,

You actually may use turbidimetry for monitoring growth provided you measure OD (usually at 600nm) within the linear response of the spec (usually OD has to be between 0 and 0.8) and provided you establish the relationship between OD and cell density (or dry weight). The main advantage of turbidimetry is that it is very quick once the system is calibrated for the organism you study. The main disadvantage is that you have to calibrate the system for every organism you intend to study and for the specific spec you use (as you actually measure light diffusion response depends on the geometry of the spec (mainly on the distance between the cuvette and the detector)).

It probably depends on the mold you are dealing with. If the mold is growing as macroscopic hyphae, turbidity is clearly not adequate (they will sediment very fast, and the turbidity across the cell will not be homogeneous anyhow)

Molds have hyphae. Their growth may be filamentous depending on the fungi. These will not be evenly suspended in the media or buffer solution that may be used for measuring in turbidimetric method. Mycelial growth when weighed as wet weight, the water content may vary depending on how much is squeezed. Also water/broth entrapped will give false result. Hence wet mycelia are washed 2-3 times with distilled water. And then dried to obtain dry weight that is measured rather than turbidimetric measurements.

Molds grow in filamentous form. Hence, it will not be evenly suspended in a buffer or medium that you will use for turbidimetric analysis. Unlike bacteria which may have unform growth in a buffer/ medium, molds may form mats at the top of the medium while others may form heavy pellets depending on the culture conditions. Hence, measuring turbidity will not prove to be useful since the media/ buffer may retain its clarity even when fungal growth is already evident.

Moulds unlike bacteria have macro and micro-structures.....with structures such as mycelia developing it will be inappropriate to use turbidimetry since they will form a mat as mentioned by Carascal..

As others explained, for measuring microbial growth by turbidity, you need a opaque (turbid) but homogeneous suspension of the microbe, as in the case of a bacterial strain. So, could you get a homogeneous suspension with your mold in culture? Please observe your growing mold culture under a microscope, to see how it grows. Good luck.

Turbidimetric method is used for bacteria because after growth you will have homogeneous solution to measure. In molds you will not be able to have this.So, Dry matter is the best.