Although membrane filtration processes have several advantages, a thorough evaluation of the process parameters influencing membrane fouling is necessary to optimize permeate flow, and ah the optimal concentration of the filtered or retained enzyme. The use of sequential separation processes $($e$.$g$.$ microfiltration and ultrafiltration$)$ can reduce the number of downstream steps, thus minimizing production costs.

In this activity, the aim is to concentrate the lipases produced by Aspergillus niger through sequential membrane separation processes, as shown below:

Culture $->$ Prefiltration $(20\backslash$mu m$)->$ Microfiltration $(0\mathrm{.}45\backslash$mu m$)->$ Ultrafiltration $($concentr$-$

ation$)$

Based on previous laboratory pilot tests with a breeding ground of Aspergillus niger, with an approximate concentration of $20$ g$/$L$,$ it has been determined that the pre$-$filter is capable of removing about $50\%$ of the biomass, which drastically reduces the viscosity of the medium to approximately $50$ cP$.$ On the other hand, the microfiltration membrane $(60$ cm$2)$ retains the rest of the biomass as well as other smells of the micron order and produces the following experimental data when operated at constant pressure $(14$ psi$)$:

Time $($s$)$ Volume $($mL$)$

$10\mathrm{.}06347\mathrm{.}9$

$60\mathrm{.}67974\mathrm{.}1$

$257\mathrm{.}72154$

$572\mathrm{.}63293$

$887\mathrm{.}74207$

$12034694$

$15185195$

$18005867$

Table $1$: Microfiltration data for A$.$ niger breeding ground

The resulting permeate is processed by tangential flow ultrafiltration in order to be concentrated. Based on the previous information, it answers as follows:

$1.$ Make a block diagram of the lipase production and recovery process Microfiltration

$2.$ Plot the change in membrane $($Rm$)$ and cake $($Rt$)$ resistances over time. Which of the two resistances is more significant? Why?

$3.$ Based on the operating volume you previously calculated for your problem situation, estimate the filtration area needed to process the culture medium within a maximum of $2$ hours

Ultrafiltration

$4.$ Make a proposal for the molecular cut$-$off size that the ultrafiltration membrane should have to retain the lipase. Justify your answer

$5.$ Whereas the permeate flux of ultrafiltration is $1\mathrm{.}6$x$102$ kg$/$m$2$s and remains relatively constant throughout the operation, making a proposal of the filtration area and process time to remove $75\%$ of the fluid. Justify your answer