What type of Algae do you have?

Thanks Alex for your response.

It is Green Algae, Scenedesmus sp.

The growth of this algae can be monitored by optical density at a wavelength of 530 nm, and verified by cell number count in cytometric (Goriajev) chamber

I have both the growth (OD) and the cell No. for periodic interval of 3 days up to 30 days.

Is it possible for you to send this reference. It will be useful for everyone in this filed.

Guillard, R.R.L. Ryther, J.H. 1962.Studies on marine

planktonic diatoms I. Cyclotella nana Hustedt and

Detonula confervacea (Cleve) Gran. Can. J. Micro. 8: 229-

239.

This paper describes about the specific growth determination.

Hi Mr. Arumugam

As for as I know, in order to find the specfic growth rate of the microalgae you need to have the biomass productivity of the particular organism in the experiment. This should be calculated only in the exponential phase of growth. The formula for calculating the specific growth rate is as follows....

μ= ln(X1/X0)/t1-t0

X1 and X0 are biomass concentration at t1 and t0 days respectively....(ln is natural log)

M. Levasseur, P.A. Thompson, P.J. Harrison, J. Phycol. 29 (1993) 587–595.

Good luck...

Thanks for your suggestion.

cell count is preferable method as temperature may affect biomass density determination through O.D. measurement. 

Dear Arumugum Muthu; The formula written above i.e. ln(x2-x1)/t2-t1 where x2 and x1 are biomass (preferably dry wt) at time t2 and t1 is correct to use. But i would say the reference of Physiological acclimation of marine phytoplankton to different nitrogen sources. J. Phycol., 29, 87-595 Levasseur never says x2 and x1 rather it has f2 and f1 as reading of fluorescence as the sample is put in a fluorometer. In your case whether you take OD or drybiomass (note in the linear phase of growth) u cant call it F1/F2. For your benefit i am sending you the same paper. you can go through once and correct me if i am wrong.

Thanks for all suggestions. Do you mean that is the exponential phase days is the important to determent the growth rate data only.

simple.. set initial OD and culture it for 15-20 days and take spec reading daily at 680nm. then put in excel days vs absorbance. then you can calculate it with this equation ln(x2-x1)/t2-t1

Hi, you may use this formula:

Specific Growth rate (u) = ln (X1-X0) / N1-N0, Where

X1= Cell number at the end of exponential phase

X0= cell number at the beginning of exponential phase

N1= number of days at the end of exponential phase

N0= number of days at the beginning of exponential phase.

You'll need to determine where the exponential growth phase is. To do that you need to plot a daily cell count (or cell density count) until you reach the late log/stationary phase.

the unit for specific growth rate is divisions/day, (d-1)

Thanks Willy Yee.

I wondered if it was also possible to use cell counts (Burker cell count) instead of biomass for the formula of μ= ln(X1/X0)/t1-t0 ?

@Bas van den Boomgaard Yes you may use cell counts as you may see the cell count values are in theory directly correlated with OD, biomass, fluorescence vs. (if the conditions are the same). So you may use cell count or OD interchangeably. Hence, you may want to observe the linearity of OD vs Cell count graph to be sure you were taking the samples adequately.

Fahri Koray Sakarya Hii

The formula about growth rate;

which nanometer do you use for chlorophyta members?

And you measure every day or othertime?

And what does "ln" means?

Can you write a sample calculation?

Thanks Dr. Sakaraya,

It is freshwater micro-algae Scenedesmus, I hope you are also working with same organism. It is now established, thanks for your response.

best regards,

Füsun Akgül hello,

we measure absorbance at 680 nm. For chlorophytes and others we use the same wavelength. A spectral analysis is better, though almost all algae cultures would give a local maximum absorbance peak around 680 nm.

Ln X is natural logarithm of the number X. At logarithmic growth, they grow exponentially over time, and logarithm of growth versus time graph should be a linear curve within log growth phase. The growth rate is (for simplicity) average logarithmic change of biomass through time. Lets say the number of cells increased 54.6-fold in 10 days. ln(X1/X0)=ln(54.6)=4

4/10 = 0.4 day^-1 is the daily growth rate.

In the previous comment I said you may use cell count and OD interchangeably. It is correct, but you need a conversion factor for using OD since it is an indirect measurement. For using OD in further experiments, one should first monitor the growth rate through both OD and cell count (dry weight if cell count is not possible). Then you may say what OD corresponds to what cell count (linear correlation, OD=a*cell count + b).

Hope this helps,

best,

koray

Thank you very much for your answer, ı will write something to your message box.

Unfortunately 680 nm is not a good wavelength as it will be affected by any changes in the chlorophyll content per cell which will the cause an error. It is best to use 720 to 750 nm

Michael A Borowitzka

Thank you very much for your answer.

I am agree with @Michael A Borowitzka.

I recommend the following for standard methods: Moheimani NR, Borowitzka MA, Isdepsky A, Fon Sing S (2013) Standard methods for measuring growth of algae and their composition. In: Borowitzka MA, Moheimani NR (eds) Algae for Biofuels and Energy. Springer, Dordrecht, pp 265-284

Excellent placement Michael A Borowitzka

Considering absorption spectra of chlorophylls and cartenoids, it is seem that the region between 540 to 600 nm is better for measurement of the broth concentration only for green algae If we want to make a measurement in the visible wavelength range.

Hossein, unfortunately your answer is incorrect. The wavelength range you mention Is in the absorption range of these pigments, so any change in pigment concentration will affect the results. Unfortunately, there are quite a number of published papers which fall into this trap and whose results are therefore somewhat in doubt. You must use 720-750 nm, or even better (and more accurate) actually count cell numbers and also measure cell dry weight.

Dear Prof. Borowizka, Thank you for your valuable comment.

Due to the low absorption of extracted pigments in this region (540-600 nm), I thought the effect of pigment content would be very small.

Thanks again for your guidance.

Yes, but there is still some absorption.

Hi Michael, I used to follow the protocol to measure the OD at 680nm, but recently I decided to use the 750nm to determine the cell density. The cell density was measured every day by a Thermo UV-vis spectrophotometer at the absorbance of 750 nm (OD750). Each sample was diluted to give an absorbance in the range 0.1-1.0 (if optical density was greater than 1.0). Microalgal cells were harvested by centrifugation and washed twice with distilled water at 3000 g for 10 minutes. The sample pellet was freeze-dried for 2 days and then the dried weight was calculated. A linear regression relationship was obtained between optical density and dried weight.

The specific growth rate (M) of the exponential phase was calculated according to the following equation: M=ln(Xt/X0)/(t-t0)

Where Xt and X0 are the cell density (dry weight) at the time of measurement (t) and the beginning of the duration ( t0 ), respectively.

I hope this answer could help.

Follow this article " https://link.springer.com/article/10.1007%2Fs11356-018-1967-5 "

Hello Arumugam Muthu

In my lab, we are working with green algae, cyanobacteria and diatoms. We do culture maintenance every day. In the beginning, we had to determine basic parameters such as growth curves and growth rates, I agree with the calculation given by Fahri Koray Sakarya. Concerning the wavelength, I can not help you because I use a flow cytometer in routine.

specific growth rate (M) =ln(Xt/X0)/(t-t0)

specific growth rate=ln Fm−ln Im/t

where , Fm is the biomass (or cell density) at time t, and Im is the initial biomass (or cell density).

What is the difference between these two equations? Eventhough both are found to be used to calculate the specific growth rate.

Neethu K V There is no difference. However, there are missing brackets in the second equation. It should be:

specific growth rate = (ln Fm - ln Im)/delta t

Fm: final mass, or Xt: biomass amount at time t

Im: initial mass, or X0: biomass amount at t0, which is the beginning of the experiments.

ln(Fm/Im) = ln Fm - ln Im

You may use any type of biomass measure; cell count, dry weight, or turbidity, or absorbance etc., as long as it is justified (it somehow measures the biomass density with good statistical reliability).

Thank you so much Fahri Koray Sakarya