Question

NS: oxygen supply in fermentation broth Calculate the amount of oxymen provided to an aerobit umure, e,pressed as godu culture-hour. 20 air, at STP conditions, is bubbled per hour into a cunure broth wolume of one Iner. Assume that only 25% of the oxygen in the bubbled a aer, due to mass transier timitalions. Show ends up dinsnived in the he calculations you performed to arrive at your at

calculate the amount of oxygen provided to an aerobic culture, expressed as mg of O2/Liz of culture-hour, if 20 L of air, at stp conditions, is bubbled per hour into the culture brother volume of one liter. Assume that only 25% of the oxygen in the bubbled air ends up dissolved in the water, due to mass transfer limitations. Show the calculations you performed to arrive to your answer.

Answer 1

20l of air bubbles /hr into 1 liter broth

Air contain 20% pure oxygen

20liter air X 20/100 = 4 liter oxygen pure oxygen provided

25% is resolved of O2 disolve

Means 4L O2 x25/100=1lit

1liter 02 disolve /liter of culture / hour

1 liter = 1000ml

1000ml of oxygen resolve /liter of culture / hour

ml/L is equivalent to part pr thousand

But the volume of gases is not equivalents to mass it can be calculated by gas law

PV=nRT

where

P

= pressure in atm (1 atm = 1000mb = 101.3 kPa)

V

= volume in liters

n

= moles of gas

R

= gas constant (for these units, =0.0821 L*atm/mol*K

T

= temperature in Kelvins ( T(K) = T(degC) + 273K )

1atmX1lit of oxygen=nX0.0821x293k

n= 1atmx1liter of oxygen/0.0821X293k

356.881molO2/liter

MW of oxygen 32.0g/mole

1 mol contain 32 g oxygen

356.881 mol contain 32x356.881

=11420.19 or 11421 g

1g =1000mg

11421x1000=

Disolve oxygen =11421x10 -3mg O2/liter of culture / hour

Provided oxygen 11421x10-3 x 4=45684 x 10-3mg 02/liter of culture / hour