Aerobic PDO process: improving sustainability Sef Heijnen, Department of Biotechnology, Faculty of Applied Sciences
F N,out = 3760969 (mol/h) The process scheme y O2,out = 0.0725 y CO2,out = 0.1614 F m,in (kg/h) = 71225 kg/h y w,out = 0.0600 p top = 1 bar Broth mass = Gas transfer: 2250 tonne O 2 = 433207 mol O 2 /h Heat = 51434 kJ/s NH 3 = 35970 mol NH 3 /h R p = 165 000 mol H 2 O = 225658 mol H 2 O/h PDO/h CO 2 = 607200 mol CO 2 /h F N,in = 3361320 (mol/h) y O2,in = 0.2100 35°C y w,in = 0 F m,out (kg/h) = 54920 kg/h y CO2,in = 0 F N,NH3 = 35970 (mol/h)
More sustainable: “pushing the limits” Less consumption/production per mol PDO of everything - Lower coefficients in the process reaction (lower variable cost) Lower DSP cost: Higher PDO concentration in broth - Glucose in feed at solubility limit Lower capital cost: Smaller fermenters - High O 2 transport rate in the fermenter: week 4 - Low O 2 /PDO ratio in process reaction
Lower q i /q p ratios: Dissect the process reaction q q µ q q q q q + + NH + + O + + + CO + H O + + + + Q s *C H O * NH * O * C H O N 1* C H O * CO * H O H * H ( heat ) 4 2 2 2 6 12 6 4 2 1 1.8 0.5 0.2 3 8 2 2 2 q q q q q q q q p p p p p p p p μ/q p · Biomass reaction + Minimize coefficients (+1) · PDO reaction by increasing q p + (-m s /q p ) · Glucose catabolism
Lowering q i /q p ratios: the kinetic approach by increasing q p by metabolic engineering Wild type Mutant q p,max 0.05 0.10 (=α) 0.04 μ opt 0.025 0.014 Metabolic 0.03 engineering q p,opt 0.023 0.059 q s / q p 1.295 0.95 0.02 q p μ / q p 1.09 0.24 0.01 q O2 / q p 2.63 1.42 c s,opt 85·10 -6 192·10 -6 0 0 0.005 0.010 0.015 0.02 0.025 0.03 0.035 μ (h -1 )
Limit of increasing q p mol s/mol p 1.4 Process reaction 1.2 strong 1.0 increasing q p 0.8 BB model PDO reaction BB model PDO reaction 0.6 is the lower limit 0.4 0.2 0 0.1 0.2 0.3 0.4 q p BB model PDO reaction -0.80 C 6 H 12 O 6 -0.80 O 2 + 1.00 C 3 H 8 O 2 + 1.80 CO 2 + H 2 O PDO
Lowering q i /q p ratios: the stoichiometric approach of metabolic engineering PDO reaction of the Black Box model: -0.80 C 6 H 12 O 6 -0.80 O 2 + 1.00 C 3 H 8 O 2 + 1.80 CO 2 + 0.80 H 2 O Catabolic part: -0.80/6 C 6 H 12 O 6 -0.80 O 2 + 0.80/6 CO 2 + 0.80/6 H 2 O Anabolic part, “substract catabolic part from PDO reaction”: -0.666 C 6 H 12 O 6 -0 O 2 + 1.00 C 3 H 8 O 2 + 1 CO 2 + 0 H 2 O
Limit of stoichiometric approach of metabolic engineering: Anaerobic holy grail Stoichiometric approach: decrease O 2 stoichiometry 0.80 mol O 2 /mol PDO à 0? Improved ATP production / O 2 • Less ATP consumption / mol PDO • …? • Theoretical PDO reaction -0.6666 C 6 H 12 O 6 – 0 O 2 + 1 C 3 H 8 O 2 + 1CO 2 + 110 kJ Gibbs energy
Limit of stoichiometric approach of metabolic engineering: Anaerobic holy grail Theoretical PDO reaction -0.6666 C 6 H 12 O 6 – 0 O 2 + 1 C 3 H 8 O 2 + 1CO 2 + 110 kJ Gibbs energy Compare: Theoretical Ethanol reaction -0.50 C 6 H 12 O 6 +1 C 2 H 6 O +1CO 2 + 112 kJ Gibbs energy Anaerobic PDO process in principle possible - More sustainable!!
Lower DSP cost: focus on less water High PDO concentration → More concentrated glucose solution: operate at glucose solubility limit → water free feedstock • Ethanol From sustainable • Methanol feedstocks • H 2 /CO syngas → High fermentation temperature to increase water evaporation
Big Banana: use mass not volume For previous calculations we used the volume approach: Which is incorrect, minor - Concentrations in mol/l error in dilute systems - Broth volume V L (m 3 ) - Volume balance However: - Volume conservation does not exist: 1 l water + 1 l ethanol ≠ 2 l mixture - Mass conservation holds: 1 kg water + 1 kg ethanol = 2 kg mixture Recommended approach: - Define concentration in mol/kg liquid - Use the total broth mass M in the fermenter - Use the total mass balance to calculate F m,out (kg/h, see PDO case) - From mass composition and thermodynamic density correlation you can calculate density, volume outflow and broth volume V L
See you in the next unit!
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