Biological Conversion of Glycerol: A New Path to Renewable Chemicals and Fuels Ramon Gonzalez Department of Chemical & Biomolecular Engineering, Department of Bioengineering, Rice University
Renewable Chemicals and Fuels Linking PetroChemical and BioBased Industries Biobased Industry
Petrochemical Industry Crude oil and natural gas
Plant biomass and wastes
Hydrocarbons
Sugars, oils, etc.
Feedstocks and intermediates Fuels: Gasoline, diesel
Chemicals Materials
• National energy security • Climate protection • Sustainability • Economic growth Biofuels:
Fuels Bulk and Specialty Chemicals
Ethanol, biodiesel
Chemicals Bio-based Materials
Fuels & Chemicals from Biorenewables Challenges
Feedstock Engineering
Feedstock Deconstruction
Microbial Fermentation
Plant Biotechnology
Pretreatment and Hydrolysis
Biocatalysis
Recovery Distillation Extraction
Metabolic Engineering (MetEng) and Metabolic Evolution (MetEvo) STRAIN CONSTRUCTION Genetic engineering (gene/pathways “knockins” & “knockouts”); Mutagenesis & Selection
MetEng/MetEvo Cycle
DESIGN Integration (systems biology), Target Identification
STRAIN CHARACTERIZATION Tubes, Flask & Bioreactors
ANALYSIS Fermentation Profiling, Functional genomics
Fluxomics
Proteomics Transcriptomics
Metrics: Concentrations (g/L), Yields (g/g), Rates (g/L/h)
Oleochemical and Biodiesel Industries Glycerol/Glycerin as Inevitable Byproduct
Yazdani and Gonzalez (2007). Curr. Opin Biotechnol. 18: 213-219.
Biodiesel and Crude Glycerol US Production & Prices
Yazdani and Gonzalez (2007) Curr. Opin Biotechnol. 18: 213-219.
Solution? The Use of Anaerobic Fermentation of Glycerol as a Platform to Produce Reduced Chemicals and Fuels
Yazdani and Gonzalez (2007) Curr. Opin Biotechnol. 18: 213-219.
Why Anaerobic Fermentation of Glycerol? Relative and Absolute Reasons • Abundant: The production of biodiesel in the U.S. increased by 10-fold in the last two years: in million gallons, from 25 (2004) to 250 (2006). Each gallon of biodiesel inevitably generates 0.75 lb of glycerol. • Inexpensive. • Renewable/Green. • New Uses/Applications Needed. • Lower Capital/Operational Costs of Anaerobic Fermentations. • Highly Reduced State of Carbon (outperform sugars: see next slide).
Glycerol vs Sugars Redox Balance
Dharmadi, Murarka, Gonzalez. Biotechnol. Bioeng., 2006: 94: 821-829. Gonzalez et al. (MS in Review); Murarka et al. App. Environ. Microbiol., 2008: 74 (4); Yazdani & Gonzalez. (2007) Curr. Opin. Biotechnol. 18: 213-219.
Current State of Knowledge on Glycerol Metabolism in Enterobacteriaceae Established model for glycerol fermentation: Glycerol-fermenting species such as Klebsiella and Citrobacter utilize a two-branch pathway; the reductive, 1,3-PDO-producing branch acts as a sink for the reducing equivalents generated in the oxidative branch.
Respiratory metabolism of glycerol: Metabolism of glycerol in species such as E. coli, which do not synthesize 1,3-PDO, takes place through a respiratory pathway that requires an external electron acceptor. Gonzalez et al. (MS in Review); Murarka et al. App. Environ. Microbiol., 2008: 74 (4); Yazdani & Gonzalez. (2007) Curr. Opin. Biotechnol. 18: 213-219.
Our Findings: E. coli Ferments Glycerol in the Absence of Electron Acceptors For nearly 80 years, researchers had believed that the metabolism of glycerol in E. coli was restricted to respiratory conditions: i.e., the presence of an external electron acceptor. • Quastel JH, Stephenson M (1925). Biochem J. 19:660. • Quastel JH, Stephenson M, Whetham MD (1925). Biochem J. 14:304. • Lin EC (1976). Annu Rev Microbiol. 30:535-78. • Booth I (2005). In Neidhardt FC et al., (ed.), E. coli and Salmonella: cellular and molecular biology, Web Edition. ASM Press, Washington, DC. Available at www.ecosal.org.
Glycerol
µ =0.041 h-1
Growth
Ethanol Other Products
Dharmadi, Murarka, Gonzalez. Biotechnol. Bioeng., 2006: 94: 821-829. Gonzalez et al. (MS in Review); Murarka et al. App. Environ. Microbiol., 2008: 74 (4); Yazdani & Gonzalez. (2007) Curr. Opin. Biotechnol. 18: 213-219.
Can we Change the Biodiesel Industry with Glycerol Fermentation? Feedstock and Operating Costs for B100 Component/Kind of Cost
Cost in $/gal. biodiesel (12/06)
Soy Oil
2.381
Methanol
0.202
Processing Costs
0.211
(Feedstock + Operating) Costs
2.794
B100 Market Price
2.750
Byproduct (Glycerin) Credit
0.021 (@0.025 $/lb)
“Byproduct Ethanol-H2/Formic credit” 0.150-0.250 “Byproduct Succinic Acid Credit”
0.600-1.000
Co-production of Ethanol-Formic Strain SY04 (pZSKLMgldA) Growth
Glycerol
EtOH Formic Byproducts
Product yields: ~ 95% (mol EtOH or formate/mol glycerol) Specific Rates: ~ 30 mmol product/gCell/h
Yazdani and Gonzalez (MS in Review)
Co-Production of: (1) EtOH-Formic or (2) EtOH-H2 Data represents close to maximum theoretical yield for all products
SY03 (pZSKLMgldA) Strain 2
SY04 (pZSKLMgldA)
Formate or Hydrogen can never be co-produced along with ethanol if sugars are used instead of glycerol. The use of glycerol results in more energy- and carbon-efficient processes. Dharmadi, Murarka, Gonzalez. Biotechnol. Bioeng., 2006: 94: 821-829. Gonzalez et al. (MS in Review); Murarka et al. App. Environ. Microbiol., 2008: 74 (4); Yazdani & Gonzalez. (2007) Curr. Opin. Biotechnol. 18: 213-219.
Ethanol-Formic and Ethanol-H2 from Glycerol * Feedstock cost is “net” for cornethanol (include revenue from coproducts) but not for glycerol-derived ethanol (does not include revenue from co-products H2 and formic acid) Capital cost significantly lower than in corn-ethanol plant. Yazdani and Gonzalez (2007) Curr. Opin Biotechnol. 18: 213-219.
Can we Change the Biodiesel Industry with Glycerol Fermentation? Feedstock and Operating Costs for B100 Component/Kind of Cost
Cost in $/gal. biodiesel (12/06)
Soy Oil
2.381
Methanol
0.202
Processing Costs
0.211
(Feedstock + Operating) Costs
2.794
B100 Market Price
2.750
Byproduct (Glycerin) Credit
0.021 (@0.025 $/lb)
“Byproduct Ethanol-H2/Formic credit” 0.150-0.250 “Byproduct Succinic Acid Credit”
0.600-1.000
Acknowledgements Graduate Students:
Postdoc:
Y. Dharmadi A. Gupta G. Durnin
S. Yazdani
A. Murarka J. Clomburg
USDA - National Research Initiative of the USDA Cooperative State Research, Education and Extension Service (2005-3550415222/16698) NSF- Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET-0601549)