MICROBIOLOGICAL ENGINEERING - QUESTION 28.3 : In the calculation of the growth o

MICROBIOLOGICAL ENGINEERING - QUESTION 28.3 : In the calculation of the growth of bacteria, absorbance, A in spectrophotometry is used. According to Beer-Lambert Law, A = e x l x c where A is the absorbance of the solution (no unit), l is the distance of light travels through the solution (in cm), e is the molar absorptivity or the molar extinction coefficient [ in L / (mol.cm) ]. For a particular solute and fixed path length : As / Ao = Cs / Co where Ao is the observed signal for a known concentration Co, and As is the observed signal for a sample concentration Cs. (a) For a cell concentration of 560 cells / mL, a spectrophotometre gives an absorbance reading of 1.0. A mixture of concentration 3600000 cells / mL can be diluted in several operations, with each operation having a dilution of 1:20. How many dilutions should be made so that the concentration of this mixture can be calculated within a range of A = 0.0 to 1.0. (b) In another experiment, a sample tube of 1 cm in width is used. Let A = 0.06 and e = 0.0012 ml / (cell.cm). Find the cell concentration of the sample.

Question Posted / kangchuentat

1 Answers
1698 Views
I also Faced
E-Mail Answers

MICROBIOLOGICAL ENGINEERING - QUESTION 28.3 : In the calculation of the growth of bacteria, absorban..

Answer / kangchuentat

MICROBIOLOGICAL ENGINEERING - ANSWER 28.3 : (a) Let Ao = 1.0, Co = 560 cells / mL, Cs = 3600000 cells / mL. By using the equation As / Ao = Cs / Co, then As = Ao x Cs / Co = 1.0 x 3600000 / 560 = 6428.57. For a dilution of 1:20, first stage dilution gives A = 6428.57 / 20 = 321.43, second stage dilution gives A = 321.43 / 20 = 16.07, third stage dilution gives A = 16.07 / 20 = 0.8, which is within a range of A = 0.0 to 1.0. Total stages of dilution needed = 3. (b) By using the equation A = e x l x c, then c = A / (e x l) = 0.06 / { [ 0.0012 ml / (cell.cm) ] x 1 cm } = 50 cells / mL. The answer is given by Kang Chuen Tat; PO Box 6263, Dandenong, Victoria VIC 3175, Australia; SMS +61405421706; chuentat@hotmail.com; http://kangchuentat.wordpress.com.

Is This Answer Correct ?

0 Yes

0 No

Post New Answer

More Chemical Engineering Interview Questions

At what temperature is glass fused to steel in the making of glass-lined equipment?

0 Answers

Question 64 – According to a heuristic of chemical engineering plant design, assume a pressure difference dP = 4 psi for each 10-ft rise in elevation. A pump is needed to pump liquid from a storage tank at a lower elevation to a heating tank at a higher elevation with the elevation difference of 60 ft. (a) Find the pressure loss due to such elevation. (b) If the required minimum inlet pressure to the heating tank is 9 psi, with 1 control valve is installed between pump and heating tank, what is the dP minimum required for the control valve and the entrance to the heating tank when the heuristic mentions that at least 10 psi is required for the control valve? (c) The pressure at the inlet of the pump is 8 psi and the flowrate of the liquid produces pressure head of 50 psi. What is the total pressure produced by the pump? (d) Assume a pipeline dP of 2 psi / 100 ft for liquid flow in a pipe according to heuristic, what is the approximate maximum length of the pipe in ft that can be installed between the pump and the heating tank?

1 Answers

Define pcbs?

0 Answers

significance of fouling factor in shell and tube heat exchnager

1 Answers

Why is steam added into the cracker in thermal cracking?

2 Answers

What are the some common problems associated with dense phase pneumatic conveying?

0 Answers

What are the methods involved to test helium leak testing in a vacuum system?

0 Answers

what is meaning of pid how it is useing controlers