S20 Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576

[B.31]

Building the perfect bioenergy feedstock for cellulosic biofuelproduction

C.N. Stewart 1,2, Jr. Stewart Jr. 1,2,∗

1 University of Tennessee, United States2 Bioenergy Science Center, United StatesKeywords: Switchgrass; Panicum virgatum; Biofuel; Biotechnol-ogy; Biosafety

Many countries, including the United States, have ambitiousgoals for significant replacement of petroleum-derived trans-portation fuels with biofuels. Cellulosic biofuels are consideredto be more desirable than those from food or feed crops for avariety of reasons, but cellulosic feedstocks are not well devel-oped: biologically, chemically, or agriculturally. Rapid and drasticmodifications will most certainly rely on biotechnology toolsenabled by genomics and systems biology research. Agricul-tural production of cellulosic feedstocks would benefit from theinclusion of domestication traits, such as dwarfing and rapidearly season growth. Many biological aspects of dedicated bioen-ergy feedstock biology will require attention; focusing on traitsthat would yield increased biomass on marginal lands. Traitsinclude increased cold-temperature photosynthesis, abiotic andbiotic stress tolerance, and delayed flowering. Plant cell wallsare the primary target for improving chemical processing andconversion. Altering how cell walls are produced and degradedwill address the sizable recalcitrance problem. Finally, transgenicplants will likely require biosafety assurance including biocon-tainment of transgenes, a prerequisite for sustainable deployment,since the same transgenes that could drastically improve feed-stocks could also exacerbate weed problem. Recent biotechnologyand genomics developments in switchgrass (Panicum virgatum)suggest that sizable improvement could be attained by engi-neering plants with just a few transgenes taking a short periodof time.

doi:10.1016/j.jbiotec.2010.08.064

[B.32]

Toxicogenomic analysis of lignin-hydrolysates: Overcominghurdles to renewable energy

R.J. Mitchell 1,∗, S. Lee 1, B.-I. Sang 2

1 Ulsan National Institute of Science and Technology, Republic of Korea2 Korea Institute of Science and Technology, Republic of KoreaKeywords: Lignin hydrolysate; Toxicogenomics; Gene expression;Bioluminescence

To answer the need for a non-food based source of fermentablesugar, researchers have focused on woody plants, which can consistof 70% or more sugar, in the form of hemicellulose and cellulose.During hydrolysis of the wood, however, the lignin fraction is alsohydrolyzed, producing aromatic acids and aldehydes, such as fer-ulic acid, coumaric acid and syringaldehyde, which are toxic to thebacterial strains and inhibit the fermentation process.

Therefore, we conducted a transcriptome analysis to determinewhich gene expression levels are perturbed in E. coli during a sub-lethal exposure to ferulic acid. Using microarray and real-timequantitative PCR (RT-qPCR), several genes were identified that areinduced within E. coli BL21(DE3) (Table 1 and Fig. 1).

Interestingly, most of the genes showing a significant induc-tion are members of the MarR regulon. To further demonstrate this,bioluminescent strains carrying fusions of two MarR-regulated pro-

Table 1Some of the genes showing a significant change in the expression levels accordingto the microarray analyses.

Genes showing a parturbed expression

aaeA Aromatic carboxylic acid efflux protein AaaeB Aromatic carboxylic acid efflux protein BaaeA Response regulator–oxidative and xenobiotic stressinaA pH-inducible protein involved in stress responsehptG Protein chaperone–heat shock responseecpD Probable pilin chaperonegroES Protein chaperone–heat shock response

Fig. 1. a) Microarry results from an exposure to 0.25 g/L ferulic acid. b) Real-timeqPCR results for the different ferulic acid concentrations tested.

Fig. 2. Growth of E. coli BL21(DE3) and bioluminescent responses of strainsBL21(DE3)/pZWF and BL21(DE3)/pSP4 when exposed to ferulic acid.

moters, zwf and inaA, with the luxCDABE genes were exposed tothese compounds (Fig. 2).

The inaA gene was induced in all three analyses (�Array, RT-qPCR and biosensor), demonstrating that the expression of thisgene is affected by ferulic acid and other hydrolysate-related com-pounds. Likewise, zwf was only mildly induced in the biosensortests, which agrees with the lack of perturbation seen in themicroarray results.

Currently, we are attempting to improve the resistance and sur-vival of this strain through over-expression of these genes andknock-out analysis.

doi:10.1016/j.jbiotec.2010.08.065