1 a A tissue culture flask containing cells is cultured in 1

1.

a.) A tissue culture flask containing cells is cultured in 10mL of media containing 0.01g/mL glucose. If the cells consume glucose at a rate of 0.01 g/hour, how long before the glucose level in the media reaches 0.001g/mL? Why does this model not accurately represent the rate at which nutrients are consumed by cells?

b.) If these cells are grown in a 10mL bioreactor which flows fresh media (containing 0.01g/mL glucose) into the system and continually ejects an equal volume of the existing media, what flow rate must be used to maintain a 0.005g/mL glucose level in the system? Assume a well-mixed system.

Solution

a) Given the starting glucose concentration of 0.01 g/ml (10 ml) the current amout of glucose present = 0.01 g.ml x 10 ml = 0.1 g glucose (present in the 10 ml media)

The final concentration status of glucose = 0.001 g/ml

The total remaining glucose = 0.001 g/ml x 10 ml = 0.01 g glucose (remining in the 10 ml media)

The amount of glucose consumed = Initial glucose amount - final glucose amount

= 0.1 - 0.01 = 0.09 g glucose

The given rate of glucose consumption = 0.01 g glucose/hour

So, the time required in consuming 0.09 g glucose will be = 0.09 g / 0.01g = 9 hours

The model does not take in account the rate of cell growth i.e. the cells grow in number more or less enponentially. And, this type o growth pattern will not keept the glucose consumption rate constant. The glucose consumption rate is a function of number of cells in the media.