Specific growth rate is defined as the increase in cell mass per unit time, e.g., grams cells (g) per gram cells (g) per hour: (). The specific growth rate is commonly given by the symbol, µ (mu), and the most common units are in reciprocal hours (h−1); however, it can also be expressed in reciprocal seconds (s−1) or minutes (min−1) or any other units of time.
Specific growth rate can be calculated from:
,
where are biomasses at the different timepoints (t1 and t2) respectively[1]
When looking for doubling time, then use that and the doubling time td is t2 - t1.
Specific growth rate constant is a way of measuring how fast the cells are dividing in a culture. It is defined on the basis of doubling rate, and mathematically it can be explained by the following formula:
k = 1/Log 2 x 1/t x (Log Nt - Log No)
it can be modified as:
k= 3.32 x 1/t x (Log Nt - Log No)
where k= growth rate constant
Nt = number of bacteria at a time t
No = number bacteria at start
t = time.