Hello, in order to measure the dry mass concentration in the fermentation broth, It is well-known that we should draw the calibration curve correlating cell concentration with absorbance deviates from a linear correlation y=ax+b. However, the value of a and b is variable, depends on yeast morphology and nature and even the growth phase.In my case, I used commercial dry yeast after 6 hours of incubation to draw the following calibration curve where a=1.07 which represents a significant difference with other works where a was around 0.34. I have double-confirmed and got same results.Does my calibration curve seem correct?
Did you fellow the same protocol used by others? Have you done appropriate dilutions to make your standard calibration curve? Your R2 =0.9653 also looks low?
Hi there,
Basically OD of cell suspension is actually a measurement of light diffusion due to the cells rather than light absorption. So the result depends on the geometry of the spec (if PM is farther from the cuvette, OD is bigger) which is not standardized (distance between PM and cuvette is not a constant therefore the same sample will give different OD value depending on this distance). So comparing data is complicated if they haven't been collected with the same apparatus.
Deat Hamid,
The measurement of biomass by spectrometric methods may be full of unexpected traps.
I have specifically studied this question in an article
Thierie J. (2014)
A Method for Exploring Suspended Particles Interactions by Means of Optical Density Measurements: Application to Bacterial Floc and Solid Nutrients - J Microb Biochem Technol 6: 279-285
(on Researchgate).
I advise you to read this little paper which takes into account the interactions between suspended cells (and / or particles).
Jacques
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