ChE  170  Homework  #2  (Due  Thursday,  October  8)    1.   Biological   Chemicals   (30   Points):   Adenosine   is   a   building   block   for   many   important  biomolecules  that  are  involved  in  cellular  energy,  cell  signaling,  and  cellular  regulation.      (a)   Draw   the   structure   of   adenosine   triphosphate   (ATP)   and   cyclic   adenosine  monophosphate  (cAMP).    (b)  ATP  is  an  important  “energy  currency”  in  cells.  With  reference  to  your  structures  above,  explain   why   ATP   is   used   by   cells   to   store   &   release   energy,   while   another   adenosine-­‐containing  molecule   like   cAMP   is   not.   (hint:   your   answer   should   include   a   discussion   of  ΔG°)      (c)  A  70  kg  adult  (~150  lbs)  could  meet  his  or  her  entire  energy  needs  for  one  day  by  eating  3  moles  of  glucose  (540  g).  Assume  that  each  molecule  of  glucose  generates  30  ATP  when  it  is   oxidized.   The   concentration   of  ATP   is  maintained   in   cells   at   about   2  mM,   and   a   70   kg  adult   has   about   25   L   of   intracellular   fluid.   Given   that   the   ATP   concentration   remains  constant  in  cells,  calculate  how  many  times  per  day  (on  average)  each  ATP  molecule  in  the  body  is  hydrolyzed  and  resynthesized.      (d)   Suppose   you   are   asked   to   formulate   a   cell-­‐based   bioprocessing   strategy   to   produce  adenosine.  What  cellular  platform  would  you  select  for  production  (without  any  additional  information)      (e)   Given  what   you   know   about   adenosine,   list   one   potential   problem  you   see  with   cell-­‐based  production  of  this  product.        2.  Comparing  Cellular  Platforms  (20  Points):  In  class,  we  talked  about  the  differences  between  two  key  model  microbes  used  in  bioprocessing.  Below,  draw  an  “engineer’s  view”  of  the  cells  and  parts  of:  

(a.)  E.  coli        (b.)  S.  cerevisiae      

       

3.  Monitoring  Cell   Growth   (10   points):   Anaerobic   gut   fungi   take   up   residence  within   the  digestive  tract  of  large  herbivores,  where  they  have  evolved  to  break  down  plant  biomass  through  the  secretion  of  powerful  enzymes.  In  class,  you  had  the  chance  to  observe  these  microbial   cells   “close   up”,   where   you   (hopefully)   observed   that   they   produce   a   very  different  looking  biomass  compared  to  yeast  and  E.  coli.  If  not,  please  see  a  picture  of  them  on  this  site:  http://omalleylab.weebly.com/research.html.      Suppose  that  you  have  isolated  a  strain  of  gut  fungi  and  you  are  proliferating  the  fungi  in  the   lab.   You  plan   to   carry   out   a   batch   growth   experiment   to   determine  doubling   time  of  these  fungi.    (a.)   What   is   one   direct   method   you   can   think   of   to   measure   cell   growth   of   these   cells?    Describe  any  disadvantages  associated  with  your  chosen  method.    (b.)  What  is  one  indirect  method  that  you  could  use  to  measure  cell  growth?  Please  explain  your  answer.      4.  Batch  Cell  Growth  (15  points):  A  strain  of  mold  was  grown  in  a  batch  culture  on  glucose  and  the  following  data  were  obtained:  Time  (hr)   Cell  Concentration  (g/L)   Glucose  Concentration  (g/L)  

0   1.25   100  9   2.45   97  16   5.1   90.4  23   10.5   76.9  30   22   48.1  34   33   20.6  36   37.5   9.38  40   41   0.63  

 For  this  system:  (a.)  Calculate  the  maximum  net  specific  growth  rate,  μmax  (b.)  Calculate  the  growth  yield,  YX/S  (c.)  What  is  the  maximum  cell  concentration  you  would  expect  if  150  g  of  glucose  were  used  with  the  same  size  inoculum?                    

5.    Batch  Cell  Growth  (25  points):  A  simple,  batch  fermentation  of  E.  coli  growing  on  an  alcohol  gave  the  results  shown  in  the  below  table:    

Time  (hour)   X  (g/L)   S  (g/L)  0   .2   9.23  2   .211   9.21  4   .305   9.07  8   .98   8.03  10   1.77   6.8  12   3.2   4.6  14   5.6   0.92  16   6.15   0.077  18   6.2   0  

 Calculate:  (a.)  Maximum  growth  rate  (μm)  (b.)  Yield  on  substrate  (YX/S)  (c.)  Mass  doubling  time  (τd)  (d.)  Saturation  constant  (KS)  (e.)  Specific  growth  rate  (μnet)  at  t  =  10  hours