Hi All. In the literature I have found that the maximum growth rate of an algae culture is calculated by determining the slope of the linear regression obtained after plotting the change in cell abundance or OD against time during the exponential phase. If I do that I am getting an slope of around 0.013 d-1 . But if I calculate the growth rate per each day during the exponential phase using the equation: mu= ln(N2/N1)/t2-t1 where N and t are the cell abundance at times 2 and 1 respectively..., then I am getting values of around 0.3 being the highest (maximum) growth rate determined in the exponential phase aprox. 0.6. Does anyone know how are these growth rates so different? Thanks!
The dry weights can also be used to calculate the growth rate of algae.
The specific growth rate is calculated ed using the following formula.
𝜇 = ln ( x1/ x 0)/ t1-t0 where x1 and x0 are the densities of algae (g/L) and the culture time t1 and t0 days. (Shuler and Kargi, 2002)
The difference between the two methods is high, check if you use for both the same units, Ln or log10, days or hours, how many couple of data have you for the regression ?
Did you calculate the regression after putting the cell numbers on a natural log based logaritmic y-axis (i.e. with base 2.718 (=exp(1))?
Hi. Thanks for the answers and suggestions. Jacco, I did calculate it that way but after the question from Gang Li and Claude Yepremian, I have just realized that I was using different time units for the two approaches...a very basic mistake! Thanks again to everybody!
I suggest you to use some software such as matlab, input your experimental data and fit the model, then you can have the result from the data fitting result.
you can refer to my paper: Biomass production and nutrients removal by a newly-isolated microalgal strain Chlamydomonas sp in palm oil mill effluent (POME)
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