Renewable Energy A: Metabolic Engineering for Biofuel Production: Genes, Enzymes and Pathways Biofuels—An Overview

1
Renewable Energy AMetabolic Engineering for
Biofuel Production Genes, Enzymes and
PathwaysBiofuelsAn Overview

• W. Malcolm Byrnes
• Howard University
• Washington, DC
• Primary Source Nature Outlook Biofuels (2011)
  Nature 474 S1-S25
• June 1, 2012

2
Outline

• Introduction
• Next Generation Biofuels
• The Food versus Fuel Controversy
• Early Movers in Advanced Biofuel Production
• Engineered Bacteria
• Biofuels from Lignocellulosic Biomass
• Biofuels from Algae
• Conclusions
• Todays Session

3
Renewable Energy

• Able to be replenished, not used up
  carbon-neutral
• Solar
• Wind
• Geothermal
• Hydrokinetic
• Biogas
• Fuel cells and hydrogen
• Biofuels
• So far, bioethanol and biodiesel most common
• On the horizon advanced biofuels
• May solve environmental and other problems

Source http//www.theenergyresources.com/the-bene
fits-of-renewable-energy-resources.shtml
4
One Route Biofuels from Biomass

• engineering plants
• understanding lignin breakdown in fungi and
  bacteria
• engineering plant lignins
• hyperstable cellulases
• chemical conversion of CO2 and hydrogen to
  hydrocarbons

Source http//www.ema.gov.sg/images/stories/biofu
els-diagram.jpg
5
Next Generation Biofuels

• First generation biofuels (ethanol and
  biodiesel) criticized higher food prices
  deforestation do little to cut GHG emissions
• IEA (May 2011) issued roadmap to ramp-up biofuel
  production from 2 to 27 by 2050 (could reduce
  CO2 emissions by 2.1 gigatons)
• What can be done?
• Next generation biofuels may help solve these
  problems
• Currently too expensive continued RD needed
• But tide is shifting due to global events
• Instability of Middle East oil
• Increased demand from developing countries
• BP Deepwater Horizon oil spill disaster
• Tsunami-induced nuclear energy crisis in Japan

6
The Food versus Fuel Conundrum

• First generation biofuels (ethanol and biodiesel)
  derived from edible parts of food crops
• Tensions over land use
• Borneo palm oil-based biodiesel
• Corn large portions of harvest diverted to
  ethanol biorefineries price spiked 73 at end of
  2010
• Ideally, biofuel crops grown on marginal land,
  but reality has been different Eg., profit often
  higher for biofuel corn
• Possible Solution advanced biofuels derived from
  non-edible parts of plants (biomass)
• Lignocellulosic feedstocks
• Energy harder to extract (cellulose bound with
  lignin)
• Enzymes more expensive
• Dedicated cropseg., Miscanthus and
  switchgrasscritical grow on minimal soil use
  little water nutrients remain in soil

7
Some Early Movers in Advanced Biofuel Production

• Mainly cellulosic ethanol
• Gruppo Mossi and Ghisolfi, April 2011 use straw
  and Novozyme enzymes to displace 34 million
  gallons of gasoline
• Mascoma, late 2011 use genetically engineered
  thermophilic microbes that secrete cellulases to
  break down cellulose
• Coskata gassify woody biomass to produce CO and
  hydrogen, which is fermented to ethanol by
  anaerobic bacteria
• Iogen use enzyme from jungle rot fungus to
  break down lignin in woody biomass of trees,
  generating ethanol
• Exxon and Synthetic Genomics (Venter) engaged in
  RD to engineer algae to produce biofuel oils
• Biorefineries can produce a range of products

8
Engineered Bacteria

• Jim Liao of UCLA engineered E. coli to produce
  butanol from glucose and protein Clostridium
  species to overproduce isobutanol cyanobacteria
  to produce butanol
• Michelle Chang of UC-Berkeley engineered E. coli
  to overproduce isobutanol by putting in genes
  from 3 other microorganisms
• Yasuo Yoshikuni (BioArchitecture Lab) used genes
  from a species of Vibrio to engineer E. coli to
  degrade, uptake and metabolize alginate from
  seaweed
• Alcohols valuable, but drop-in fuels best
• Especially needed for heavier vehicles and
  aircraft
• Using cyanobacteria to produce alkanes (LS9,
  George Church)
• Using algae to produce oils
• Plant oils from seeds and leaves

Butanol from glucose
Escherichia coli
Source DOE website
Source Yan and Liao (2009) JIMB 36 471-479.
9
Biofuels from Lignocellulosic Biomass

• Woody stems of plants contain lignocellulosic
  material cellulose, hemicellulose and lignin
• Cellulose ? ethanol other alcohols
• But cellulose and hemicellulose held tightly by
  lignin, a complex polymer
• Currently lignocellulosic material broken apart
  by heat and chemicals
• Simon McQueen-Mason of York discovering genes
  for cellulases in Limnoria quadripunctata, which
  can digest wood without bacterial symbionts
• Dominique Loque of JBI in Emeryville engineering
  plants to redistribute lignin or produce weaker
  lignins
• Brad Holmes of JBI using ionic liquids to
  dissolve lignin in biomass
• But ions must be removed prior to enzymatic and
  fermentation steps
• John Hartwig and Alexey Sergeev of UI using a
  nickel catalyst to modify lignins by removing
  oxygen from them
• Potential problems source and transport of
  biomass feedstock enzyme transport

Sources top, feedstocks.pss.msstate.edu bottom,
www.sfi.mtu.edu/FutureFuelfromForest/Lignocellulos
icBiomass.htm
10
Biofuels from Algae

• Algae could yield 61,000 liters of biofuel oil
  per hectare
• Could replace 17 of US petroleum imports
• Challenges
• Space only 5.5 of land in US suitable for
  algae-growing ponds
• Water huge amounts needed
• Possible solutions
• strains that grow in wastewater or salt water
• closed photobioreactors and siting near CO2
  source
• Jim Liao use algae as food (protein) for
  engineered E. coli that produce long chain
  alcohols
• George Church of Harvard grow cyanobacteria
  engineered to produce hydrocarbons

Sources top, biomassauthority.com/biodiesel-from-
algae/ bottom, biofuels.asu.edu/images/biomateria
ls-figure1.jpg
11
Conclusions

• next generation biofuels hold great promise for
  the future
• Each type of biofuel has pros and cons
  therefore, diversity of types approaches needed
• Can serve as transitional fuels, and fuels for
  heavier vehicles and aircraft
• Intensified research funding critical greater
  investment by companies government incentives
• Part of a multi-pronged approach toward achieving
  energy sustainability

12
Todays Session
unfortunately, Qing Xu (engineering
cyanobacteria for hydrogen production) cannot
attend.