Renewable Energy A Metabolic Engineering for Biofuel Production Genes_ Enzymes and Pathways Biofuels—An Overview.ppt

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					                   Renewable Energy A:
                   Metabolic Engineering for
                   Biofuel Production: Genes,
                   Enzymes and Pathways

                   Biofuels—An Overview
W. Malcolm Byrnes
Howard University
Washington, DC
Primary Source: Nature Outlook: Biofuels (2011) Nature 474: S1-
June 1, 2012
o   Introduction
o   “Next Generation” Biofuels
o   The Food versus Fuel Controversy
o   Early Movers in Advanced Biofuel Production
o   Engineered Bacteria
o   Biofuels from Lignocellulosic Biomass
o   Biofuels from Algae
o   Conclusions
o   Today’s Session
                 Renewable Energy
                                                             o   Able to be replenished, not
                                                                 used up; carbon-neutral
                                                             o   Solar
                                                             o   Wind
                                                             o   Geothermal
                                                             o   Hydrokinetic
                                                             o   Biogas
                                                             o   Fuel cells and hydrogen
                                                             o   Biofuels
                                                                  n   So far, bioethanol and
                                                                      biodiesel most common
                                                                  n   On the horizon: advanced
                                                                  n   May solve environmental
                                                                      and other problems
One Route: Biofuels from Biomass

                     o engineering plants
   *           *     o understanding
                       lignin breakdown in
                       fungi and bacteria
                     o engineering plant
           *           lignins
       *             o hyperstable
                     o chemical
                       conversion of CO2
                       and hydrogen to

“Next Generation” Biofuels
o “First generation” biofuels (ethanol and biodiesel)
    criticized: higher food prices; deforestation; do little to cut
    GHG emissions
o   IEA (May 2011) issued roadmap to ramp-up biofuel
    production: from 2% to 27% by 2050 (could reduce CO2
    emissions by 2.1 gigatons)
o   What can be done?
o   “Next generation” biofuels may help solve these problems
o   Currently too expensive; continued R&D needed
o   But tide is shifting due to global events:
     n Instability of Middle East oil
     n Increased demand from developing countries
     n BP Deepwater Horizon oil spill disaster
     n Tsunami-induced nuclear energy crisis in Japan
The Food versus Fuel
Conundrum      First generation biofuels (ethanol and
               biodiesel) derived from edible parts
               of food crops
                         o Tensions over land use:
                             n Borneo palm oil-based biodiesel
                             n Corn: large portions of harvest
                                diverted to ethanol biorefineries;
                                price spiked 73% at end of 2010
                         o Ideally, biofuel crops grown on
                           marginal land, but reality has been
                           different: Eg., profit often higher for
                           biofuel corn
                         o Possible Solution: advanced biofuels
                           derived from non-edible parts of
                           plants (biomass)
                             n Lignocellulosic feedstocks
                             n Energy harder to extract
                                (cellulose bound with lignin*)
                             n Enzymes more expensive
                         o Dedicated crops—eg., Miscanthus
                           and switchgrass—critical; grow on
                           minimal soil; use little water;
                           nutrients remain in soil
Some Early Movers in
Advanced Biofuel Production
o Mainly cellulosic ethanol
o Gruppo Mossi and Ghisolfi, April 2011: use straw and
    Novozyme enzymes to displace 34 million gallons of
o   Mascoma, late 2011: use genetically engineered
    thermophilic microbes that secrete cellulases* to break
    down cellulose
o   Coskata: gassify woody biomass to produce CO and
    hydrogen, which is fermented to ethanol by anaerobic
o   Iogen: use enzyme from “jungle rot” fungus to break down
    lignin in woody biomass of trees, generating ethanol
o   Exxon and Synthetic Genomics (Venter): engaged in R&D
    to engineer algae to produce biofuel oils
o   “Biorefineries” can produce a range of products
             Engineered Bacteria
                             o   Jim Liao of UCLA: engineered E.
                                 coli to produce butanol from glucose
                                 and protein; Clostridium species to
       Butanol from              overproduce isobutanol;
       glucose                   cyanobacteria to produce butanol
                             o   Michelle Chang of UC-Berkeley:
                                 engineered E. coli to overproduce
                                 isobutanol by putting in genes from
                                 3 other microorganisms
                             o   Yasuo Yoshikuni (BioArchitecture
                                 Lab): used genes from a species of
                                 Vibrio to engineer E. coli to degrade,
                                 uptake and metabolize alginate from
Escherichia coli             o   Alcohols valuable, but “drop-in fuels”
                                   n   Especially needed for heavier
                                       vehicles and aircraft
                                   n   Using cyanobacteria to produce
                                       alkanes (LS9, George Church)
                                   n   Using algae to produce oils
                                   n   Plant oils from seeds and
Source: DOE website
                           Source: Yan and Liao (2009) JIMB 36: 471-479.
                     Biofuels from Lignocellulosic
                     Biomass       Woody stems of plants contain lignocellulosic
                                   material: cellulose, hemicellulose and lignin
                                                       o   Cellulose → ethanol + other alcohols
                                                       o   But cellulose and hemicellulose held tightly
                                                           by lignin, a complex polymer
                                                       o   Currently lignocellulosic material broken apart
                                                           by heat and chemicals
                                                       o   Simon McQueen-Mason of York: discovering
                                                           genes for cellulases in Limnoria
                                                           quadripunctata, which can digest wood
                                                           without bacterial symbionts
                                                       o   Dominique Loque of JBI in Emeryville:
                                                           engineering plants to redistribute lignin or
                                                           produce weaker lignins
                                                       o   Brad Holmes of JBI: using “ionic liquids” to
                                                           dissolve lignin in biomass
                                                             n   But ions must be removed prior to
                                                                 enzymatic and fermentation steps*
                                                       o John Hartwig and Alexey Sergeev of UI:
                                                         using a nickel catalyst to modify lignins by
                                                         removing oxygen from them*
                                                       o Potential problems: source and transport of
                                                         biomass feedstock; enzyme transport

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

Sources: top,; bottom,
o   “next generation” biofuels hold great promise
    for the future
o   Each type of biofuel has pros and cons;
    therefore, diversity of types & approaches
o   Can serve as “transitional” fuels, and fuels for
    heavier vehicles and aircraft
o   Intensified research funding critical; greater
    investment by companies; government
o   Part of a multi-pronged approach toward
    achieving energy sustainability
          Today’s Session
           8:15                               Plants as renewable sources
                          John Dyer
           a.m.                               of biofuels
           8:45           Ed                  Enzyme design for lignin
           a.m.           Eisenstein          engineering
           9:15                       Plant biomass conversion
                          Jason Sello
           a.m.                       using Streptomyces
           10:00                              The quest for hyperthermo-
                          Frank Robb
           a.m.                               stable cellulases
           10:30                              A 2-step hydrocarbon
                          David Drab
           a.m.*                              synthesis from CO2 and H2
*unfortunately, Qing Xu (engineering cyanobacteria for hydrogen production) cannot attend.

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