Max Planck Institute Magdeburg Max Planck Institute Magdeburg Investigation of an integrated racemization/separation process for the production of enantiomerically pure mandelic acid García-Rivera M. 1 , Wrzosek K. 2 , Renken A. 1 , Seidel-Morgenstein A. 2,3 MAX-PLANCK-INSTITUT DYNAMIK KOMPLEXER TECHNISCHER SYSTEME MAGDEBURG 1 EPFL Swiss Federal Institute of Technology, Lausanne/Switzerland 2 Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg/Germany 3 Chair for Process Systems Engineering, Otto-von-Guericke University Magdeburg/Germany August 2015 1
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Max Planck Institute Magdeburg
Investigation of an integrated racemization/separation process for the production
essences, drugs• Single enantiomers enantiomerically
pure compounds
CephalosporinSertraline Penicillin
(S)-mandelic acid (R)-mandelic acid
O
OHOH
O
OHOH
Duloxetine
• Skin treatments, urinary antiseptic• Precursors for vanillin production and thrombin inhibitors• Resolution of other racemates
Mandelic acid and derivatives
Max Planck Institute Magdeburg 4August 2015
Introduction
Pure enantiomers
from
through through
Classical resolution
Kinetic resolution
Dynamic kinetic resolution
� 50% yield
� 50% yield
�100% yield
Crystallization
Chromatography
L-L extraction
Membrane separation
Non-synthetic Synthetic
Chiral or achiral compounds Racemates
Resolution techniques
Asymmetric catalysts
Biocatalysts
Chiral auxiliaries
Chiral pool
Enantioselective synthesis
1.
Enantiopure compounds production[1,2]
Integrated processes
Max Planck Institute Magdeburg 5August 2015
Integrated racemization-separation process
Integrated processes[3]
• Overcome 50% yield 100%• Cost-effective methods• Racemization, chromatography and crystallization• Versatility in operation configurations• Suitable conditions for all the operations
2.
Enzymatic racemization
Enantioselective chromatography
R-enantiomer
R -enantiomer S- enantiomerRacemate
R+S
Selected integrated process
Integrated process
Suitable conditions
Max Planck Institute Magdeburg 6
Enzymatic racemization
August 2015
Integrated racemization-separation process2.
Enantioselective chromatography
• Mandelate racemase• Well studied and characterized• Broad spectrum of mandelic acid
derivatives as substrate• Mild reaction conditions• Recombinant expression in E. coli [4]
• Immobilized for easy reuse
• Chirobiotic® T• Teicoplanin/silica gel as stationary
chiral phase
• Commercially available• Highly enantioselective• Variety of enantiomers
• Proper selection of a compatible mobile phase for both operations
Octamer with ~ 39 kDa identical monomers
Macrocyclic glycopeptide
Complex chiral environment
Hydrogen bonding sites
Active site within a hydrophobic cavity
Max Planck Institute Magdeburg 7August 2015
Enzymatic racemization3.
(R)-mandelic acid (R)-mandelic acidcomplex
Planar enolateintermediate
(S)-mandelic acidcomplex
(S)-mandelic acid
O
OHOH
O
OHOH
NNH
His 297NH3
+
Lys 166
H
O
O
Glu 317
NH3+
Lys 164
Mg2+
H
O O-
OH Asn 197
: NH+
NH
His 297
NH3+
Lys 166
H
O
O
Glu 317
NH3+
Lys 164
Mg2+
H
O-
O-
O Asn 197
Racemization mechanism[5,6]
NH+
NH
His 297NH2
Lys 166
H
O
O
Glu 317
NH3+
Lys 164
Mg2+
H
O O-
O
HAsn 197
:
Active site in hydrophobic cavity [7]
Max Planck Institute Magdeburg 8August 2015
Enzymatic racemization3.
1 U amount of enzyme that catalyzes 1 µmol of substrate in 1 minute under determined conditions
0 20 40 60 80 100 120 140 160 180 200
CR,0 [mM]
Initi
al re
actio
n ra
te [U
]
First-order reaction
Zero-order reaction
Michaelis-Menten kinetics[8] (irreversible)
R + E C S + Ek-R
kR
kS
−𝑑𝐶𝑅
𝑑𝑡 =𝑽𝒎𝒂𝒙𝐶𝑅
𝐶𝑅+𝑲𝑴 𝑽𝒎𝒂𝒙=𝑘𝑆𝐶𝐸
Enzymatic activity, in U1
• Maximum catalytic potential• Determined temperature, pH and initial substrate concentration• Initial reaction rate used in kinetics
Max Planck Institute Magdeburg 9August 2015
Enzymatic racemization3.
Reversible Michaelis-Menten kinetics [8,9]R + E C S + E
k-R
kR
kS
k-S
−𝑑𝐶𝑅
𝑑𝑡 =𝑉𝑚𝑎𝑥 (𝐶𝑅−𝐶𝑆 )𝐾𝑀+𝐶𝑅+𝐶𝑆
Simplified model
Substrate inhibition
−𝑑𝐶𝑅
𝑑𝑡 =𝑽 ′𝒎𝒂𝒙 (𝐶𝑅−𝐶𝑆 )
𝑲 ′𝑴+𝐶𝑅+𝐶𝑆+𝐶𝑅
𝑲 𝒊(𝐶𝑅+𝐶𝑆)
𝑘𝑆=𝑘𝑅 𝑘−𝑆=𝑘−𝑅
𝑽𝒎𝒂𝒙=𝑘𝑆𝐶𝐸
R + E C S + EkR
k-S
RC
+R
Ki
k-RkS
No distinction between enantiomers: and
Ineffective binding at high substrate concentration
𝑽 ′𝒎𝒂𝒙=𝑘𝑆𝐶𝐸
Max Planck Institute Magdeburg 10August 2015
Application on a fixed-bed reactor4.
Enzyme immobilization
• Solid porous carrier• Easy reuse• Versatility of reactor configuration• Mass transfer effects• Apparent kinetic parameters:
• Static volume• PFR outlet (non-reacting)• Measured only once
Constant inlet
Polarimeter
Constant outlet
Max Planck Institute Magdeburg 17August 2015
Experimental
• Immobilized enzyme storage• Sampling at 2, 4, 6, 8, 10 and 12 min• Reaction stopped by filtering and heating up to 90 °C• Analytical HPLC measurement: Chirobiotic® T
5.
8 mL substrate
60 mg wet carrier
0 2 4 6 8 10 12 140
500
1000
1500
2000
2500
3000
3500
Time (min)
Subs
trat
e co
nsum
ptio
n (m
mol
/gca
rrie
r)
initial rate enzymatic activity
HPLC method
Enzymatic activity
Free enzyme Immobilized enzyme
Polarimetry method Enzyme characterization Kinetics from batch reactor
HPLC method - Storage stability
Protein concentration Bradford method[10] Mass balance
Max Planck Institute Magdeburg 18August 2015
Experimental
Cell growth
5.
Protein identification
Max Planck Institute Magdeburg 19August 2015
5 L culture 20 g dry adsorbent 60 g wet carrier
= 3x weight of dry adsorbent
337 mg protein
+
Enzyme production
Results6.
Immobilization yields
• Immobilized protein recovery: • Activity recovery:
Remaining protein in eluent
Total available protein1 -100 * ( ) = 50% Activity in total mass of wet carrier
Activity in total volume of extract100 * ( ) = 48%
Max Planck Institute Magdeburg
Free enzyme storage
20August 2015
Results
Immobilized enzyme storage(measured by polarimetry method) (measured by HPLC method)
6.
Activity at time t
Initial activity)
Activity retention = 100 * (
• Best storage at -20°C• Good activity retention after 60 days
• Best storage with Tris HCl buffer• Good activity retention after 70 days
Max Planck Institute Magdeburg 21August 2015
Results6.
Initial substrate concentration, CR,0 [mM]
Initial substrate concentration, CR,0 [g/L]
Initi
al re
actio
n ra
te,
[U/g
carr
irer]
ExperimentalNonlinear fit r2 = 0.9355
ExperimentalNonlinear fit r2 = 0.8999
Initial substrate concentration, CR,0 [mM]
Initial substrate concentration, CR,0 [g/L]
−𝑑𝐶𝑅
𝑑𝑡 |0=𝑉𝑚𝑎𝑥
𝑎𝑝𝑝 𝐶𝑅 , 0
𝐾𝑀𝑎𝑝𝑝+𝐶𝑅 , 0
−𝑑𝐶𝑅
𝑑𝑡 |0=
𝑉 ′𝑚𝑎𝑥𝑎𝑝𝑝 𝐶𝑅 ,0
𝐾 ′𝑀𝑎𝑝𝑝+𝐶𝑅 ,0+𝐶𝑅 , 0
2
𝐾 𝑖
Kinetics without substrate inhibition(measured by polarimetry method) (measured by polarimetry method)
Kinetics with substrate inhibition
Max Planck Institute Magdeburg 22August 2015
Results6.
Kinetics without substrate inhibition(measured by polarimetry method) (measured by polarimetry method)
Kinetics with substrate inhibition
Kinetic model at chromatographic conditionsa or or Ki r2 b
No substrate inhibition 169.46 ± 5.07 U/gcarrier 8.59 ± 1.24 mM - 0.9355
Substrate inhibition 330.09 ± 17.13 U/gcarrier 30.61 ± 4.78 mM 95 mM 0.8999a 20 mM HEPES 3.3 mM MgCl2 20%v MeOH pH=6.80b Correlation coefficient for nonlinear fit. For best fit r2 ~1
−𝑑𝐶𝑅
𝑑𝑡 |0=𝑉𝑚𝑎𝑥
𝑎𝑝𝑝 𝐶𝑅 , 0
𝐾𝑀𝑎𝑝𝑝+𝐶𝑅 , 0
−𝑑𝐶𝑅
𝑑𝑡 |0=
𝑉 ′𝑚𝑎𝑥𝑎𝑝𝑝 𝐶𝑅 ,0
𝐾 ′𝑀𝑎𝑝𝑝+𝐶𝑅 ,0+𝐶𝑅 , 0
2
𝐾 𝑖
Max Planck Institute Magdeburg 23August 2015
Results6.
PFR prediction without substrate inhibition
PFR prediction with substrate inhibition
(2𝑲 ′𝑴𝒂𝒑𝒑+2𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 ,0+𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 ,0
2
𝑲 𝒊 ) ln ( 2𝐶𝑅 (𝜏)−𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 , 0
2𝐶𝑅 , 0−𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 ,0)+2(𝐶𝑅(𝜏 )−𝐶𝑅 ,0)=−
4𝜏𝑽 ′𝒎𝒂𝒙𝒂𝒑𝒑 𝑲 𝒊
𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 , 0
𝐶𝑅(𝜏 )=12 𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 , 0 (1+𝑒𝑒𝑅 , 0𝑒
− 2𝑘𝑜𝑣𝑒𝑟𝑎𝑙𝑙, 𝑃𝐹𝑅𝝉 )
𝑘𝑜𝑣𝑒𝑟𝑎𝑙𝑙 ,𝑃𝐹𝑅=𝑽𝒎𝒂𝒙
𝒂𝒑𝒑
𝑲𝑴𝒂𝒑𝒑+𝐶𝑜𝑣𝑒𝑟𝑎𝑙𝑙 ,0
𝐷𝑃𝐹𝑅
Inlet concentration [g/L]
Enantiomeric excess
koverall,PFR [1/min]
20 100%eeR
1.6720 60%eeR
20 40%eeR
20 100%eeS
40 100%eeR 0.86
𝐷𝑃𝐹𝑅=¿1512 gcarrier/Lsolution
Max Planck Institute Magdeburg 24August 2015
Results6.
PFR prediction without substrate inhibition(measured by polarimetry method) (measured by polarimetry method)
PFR prediction with substrate inhibition
(R)-m
ande
lic a
cid
conc
entr
atio
n, C
R [g
/L]
Residence time, τ [min] Residence time, τ [min]
• More accurate prediction of CR
• Good performance for all %ee
• Deviation in 100%ee prediction• Good performance for 60 and 40%ee
Coverall,0 = 20 g/L Coverall,0 = 20 g/L
Max Planck Institute Magdeburg 25August 2015
Results6.
PFR prediction without substrate inhibition(measured by polarimetry method) (measured by polarimetry method)
PFR prediction with substrate inhibition
Subs
trat
e co
ncen
trat
ion,
CR o
r CS [
g/L]
Residence time, τ [min] Residence time, τ [min]
• More accurate prediction of CR
• Incapability for prediction of CS
• Simplified model considers only R→S
• Slower reaction rate due to inhibition• Matches with S→R reaction• No accurate prediction of any
Covereall,0 = 20 g/L Coverall,0 = 20 g/L
Max Planck Institute Magdeburg 26August 2015
Results6.
PFR prediction without substrate inhibition(measured by polarimetry method) (measured by polarimetry method)
PFR prediction with substrate inhibition
Subs
trat
e co
ncen
trat
ion,
CR o
r CS [
g/L]
Residence time, τ [min]
• 100%ee of R-mandelic acid• Faster reaction rate predicted• 40 g/L is under substrate inhibition
• 100%ee of R-mandelic acid• Slower reaction rate predicted• Overestimation of inhibition
Coverall,0 = 40 g/L
Max Planck Institute Magdeburg 27August 2015
Conclusions and outlook7.
• Immobilized mandelate racemase presented improved storage stability in comparison with the free-enzyme form
• Good operational stability and ease of reuse when used in different reactor configurations
• Effective prediction of fixed-bed reactor behavior with no-inhibition model up to CR,0 = 20 g/L
• Accurate prediction even with different initial enantiomeric excesses
Conclusions
Outlook
• Non-simplified kinetic model: consideration of kinetic parameters for both reaction directions R → S and S → R
• Non-ideality of the fixed-bed reactor: external and internal mass transfer effects, residence time distribution deviations
• Feasibility for coupling with crystallization: solubility of pure enantiomers in mobile phase
Max Planck Institute Magdeburg 28August 2015
References
1. Todd, M.H., Separation of enantiomers. Synthetic methods. 2014: Wiley-VCH.
2. Lorenz, H. and A. Seidel-Morgenstern, Processes To Separate Enantiomers. Angewandte Chemie International Edition, 2014. 53(5): p. 1218-1250.
3. Kaspereit, M., S. Swernath, and A. Kienle, Evaluation of Competing Process Concepts for the Production of Pure Enantiomers. Organic Process Research & Development, 2012. 16(2): p. 353-363.
4. Narmandakh, A. and S.L. Bearne, Purification of recombinant mandelate racemase: Improved catalytic activity. Protein Expression and Purification, 2010. 69(1): p. 39-46.
5. Bearne, S.L. and R.J. Spiteri, Reduction of intrinsic kinetic and thermodynamic barriers for enzyme-catalysed proton transfers from carbon acid substrates. Journal of Theoretical Biology, 2005. 233(4): p. 563-571.
6. Nagar, M., et al., Potent Inhibition of Mandelate Racemase by a Fluorinated Substrate-Product Analogue with a Novel Binding Mode. Biochemistry, 2014. 53(7): p. 1169-1178.
7. Lietzan, A.D., et al., Structure of Mandelate Racemase with Bound Intermediate Analogues Benzohydroxamate and Cupferron. Biochemistry, 2012. 51(6): p. 1160-1170.
8. Cornish-Bowden, A., Fundamentals of Enzyme Kinetics, ed. P. Press. 2004, London.
9. Illanes, A., Enzyme biocatalysis. Principles and applications. 2008: Springer Science and Business Media B.V.
10. Bradford, M.M., A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Analytical Biochemistry, 1976. 72(1–2): p. 248-254.
Max Planck Institute Magdeburg 29August 2015
Free and immobilized enzyme kinetics
−𝑑𝐶𝑅
𝑑𝑡 |0=
𝑽𝒎𝒂𝒙𝒂𝒑𝒑 𝐶𝑅 ,0
𝑲𝑴𝒂𝒑𝒑+𝐶𝑅 ,0
Kinetics free enzyme(measured by polarimetry method) (measured by polarimetry method)
169.46± 5.07 71.21 ± 2.13 8.59 ± 1.24 1 from previous results, not measured in this study2 50 mM HEPES 3.3 mM MgCl2 pH=7.503 20 mM HEPES 3.3 mM MgCl2 20%v MeOH pH=6.80