Joseph J. Bozell

Technology development for the production of biobased products from biorefinery carbohydrates—the US Department of Energy’s “Top 10” revisited

A biorefinery that supplements its manufacture of low value biofuels with high value biobased chemicals can enable efforts to reduce nonrenewable fuel consumption while simultaneously providing the necessary financial incentive to stimulate expansion of the biorefining industry. However, the choice of appropriate products for addition to the biorefinerys portfolio is challenged by a lack of broad-based conversion technology coupled with a plethora of potential targets. In 2004, the US Department of Energy (DOE) addressed these challenges by describing a selection process for chemical products that combined identification of a small group of compounds derived from biorefinery carbohydrates with the research and technology needs required for their production. The intent of the report was to catalyze research efforts to synthesize multiple members of this group, or, ideally, structures not yet on the list. In the six years since DOEs original report, considerable progress has been made in the use of carbohydrates as starting materials for chemical production. This review presents an updated evaluation of potential target structures using similar selection methodology, and an overview of the technology developments that led to the inclusion of a given compound. The list provides a dynamic guide to technology development that could realize commercial success through the proper integration of biofuels with biobased products.

Comparative genome analysis of lignin biosynthesis gene families across the plant kingdom.

BackgroundAs a major component of plant cell wall, lignin plays important roles in mechanical support, water transport, and stress responses. As the main cause for the recalcitrance of plant cell wall, lignin modification has been a major task for bioenergy feedstock improvement. The study of the evolution and function of lignin biosynthesis genes thus has two-fold implications. First, the lignin biosynthesis pathway provides an excellent model to study the coordinative evolution of a biochemical pathway in plants. Second, understanding the function and evolution of lignin biosynthesis genes will guide us to develop better strategies for bioenergy feedstock improvement.ResultsWe analyzed lignin biosynthesis genes from fourteen plant species and one symbiotic fungal species. Comprehensive comparative genome analysis was carried out to study the distribution, relatedness, and family expansion of the lignin biosynthesis genes across the plant kingdom. In addition, we also analyzed the comparative synteny map between rice and sorghum to study the evolution of lignin biosynthesis genes within the Poaceae family and the chromosome evolution between the two species. Comprehensive lignin biosynthesis gene expression analysis was performed in rice, poplar and Arabidopsis. The representative data from rice indicates that different fates of gene duplications exist for lignin biosynthesis genes. In addition, we also carried out the biomass composition analysis of nine Arabidopsis mutants with both MBMS analysis and traditional wet chemistry methods. The results were analyzed together with the genomics analysis.ConclusionThe research revealed that, among the species analyzed, the complete lignin biosynthesis pathway first appeared in moss; the pathway is absent in green algae. The expansion of lignin biosynthesis gene families correlates with substrate diversity. In addition, we found that the expansion of the gene families mostly occurred after the divergence of monocots and dicots, with the exception of the C4H gene family. Gene expression analysis revealed different fates of gene duplications, largely confirming plants are tolerant to gene dosage effects. The rapid expansion of lignin biosynthesis genes indicated that the translation of transgenic lignin modification strategies from model species to bioenergy feedstock might only be successful between the closely relevant species within the same family.

Biomass Oil Analysis: Research Needs and Recommendations

Abstract : Report analyzing the use of biomass oils to help meet Office of the Biomass Program goals of establishing commercial biorefinery by 2010 and commercializing at least four biobased products.

A Comparative Review of Petroleum‐Based and Bio‐Based Acrolein Production

Acrolein is an important chemical intermediate for many common industrial chemicals, leading to an array of useful end products. This paper reviews all the synthetic methods, including the former (aldol condensation) and contemporary (partial oxidation of propylene) manufacturing methods, the partial oxidation of propane, and most importantly, the bio-based glycerol-dehydration route. Emphasis is placed on the petroleum-based route from propylene and the bio-based route from glycerol, an abundantly available and relatively inexpensive raw material available from biodiesel production. This review provides technical details and incentives for industrial proyduction that justify a transition toward bio-based acrolein production.

Efficient Cobalt-Catalyzed Oxidative Conversion of Lignin Models to Benzoquinones

Phenolic lignin model monomers and dimers representing the primary substructural units of lignin were successfully oxidized to benzoquinones in high yield with molecular oxygen using new Co-Schiff base catalysts bearing a bulky heterocyclic nitrogen base as a substituent. This is the first example of a catalytic system able to convert both S and G lignin model phenols in high yield, a process necessary for effective use of lignin as a chemical feedstock.

Predicting Enzyme Adsorption to Lignin Films by Calculating Enzyme Surface Hydrophobicity

Background: Lignin is a plant cell wall polymer that inhibits enzymatic saccharification of polysaccharides for the production of biofuel. Results: The adsorption of enzymes to lignin surfaces correlates to solvent-exposed hydrophobic clusters. Conclusion: Hydrophobicity, not surface charge, identifies proteins that preferentially adsorb to lignin. Significance: The method could be used to design improved cellulase cocktails to lower the cost of biofuel production. The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production.

High-performance liquid chromatography/high-resolution multiple stage tandem mass spectrometry using negative-ion-mode hydroxide-doped electrospray ionization for the characterization of lignin degradation products.

In the search for a replacement for fossil fuel and the valuable chemicals currently obtained from crude oil, lignocellulosic biomass has become a promising candidate as an alternative biorenewable source for crude oil. Hence, many research efforts focus on the extraction, degradation, and catalytic transformation of lignin, hemicellulose, and cellulose. Unfortunately, these processes result in the production of very complex mixtures. Further, while methods have been developed for the analysis of mixtures of oligosaccharides, this is not true for the complex mixtures generated upon degradation of lignin. For example, high-performance liquid chromatography/multiple stage tandem mass spectrometry (HPLC/MS(n)), a tool proven to be invaluable in the analysis of complex mixtures derived from many other biopolymers, such as proteins and DNA, has not been implemented for lignin degradation products. In this study, we have developed an HPLC separation method for lignin degradation products that is amenable to negative-ion-mode electrospray ionization (ESI doped with NaOH), the best method identified thus far for ionization of lignin-related model compounds without fragmentation. The separated and ionized compounds are then analyzed by MS(3) experiments to obtain detailed structural information while simultaneously performing high-resolution measurements to determine their elemental compositions in the two parts of a commercial linear quadrupole ion trap/Fourier-transform ion cyclotron resonance mass spectrometer. A lignin degradation product mixture was analyzed using this method, and molecular structures were proposed for some components. This methodology significantly improves the ability to analyze complex product mixtures that result from degraded lignin.

Characterization of organosolv switchgrass lignin by using high performance liquid chromatography/high resolution tandem mass spectrometry using hydroxide-doped negative-ion mode electrospray ionization

Lignin is an aromatic biopolymer that may yield valuable chemicals currently obtained solely from petroleum. However, extraction of lignin by using traditional methods, such as organosolv extraction, produces very complex mixtures. Molecular level characterization of the major components is essential to be able to rationally tailor methodology for the conversion of these mixtures to transportation fuel and valuable chemicals. In this study, high performance liquid chromatography/high resolution tandem mass spectrometry (HPLC/MSn) was used to obtain molecular weight, elemental composition and structural information for the major components in an organosolv lignin sample. HPLC/MSn coupled with hydroxide-doped electrospray ionization was used to identify the structures of the major components by using a Thermo Scientific linear quadrupole ion trap-Fourier transform ion cyclotron resonance hybrid mass spectrometer (LQIT/FT-ICR). The results reported here demonstrate that the major products of organosolv extraction are low molecular weight compounds, including monomeric and dimeric lignin units, with various functionalities.

A study of poplar organosolv lignin after melt rheology treatment as carbon fiber precursors

Lignins from various poplar genotypes were isolated by using organosolv fractionation and subjected to rheological treatment at various temperatures. Physicochemical characterization of the lignin variants shows a broad distribution of glass transition temperatures, melt viscosity, and pyrolysis char residues. Rheological treatment at 170 °C induces lignin repolymerization accompanied with an increase in condensed linkages, molecular weights, and viscosities. In contrast, rheology testing at 190 °C results in the decrease in lignin aliphatic and phenolic hydroxyl groups, β-O-aryl ether linkages, molecular weights, and viscosity values. Lignin under air cooling generates more oxygenated and condensed compounds, but lower amounts of ether linkages than lignin cooled under nitrogen. Lignin with a lower syringyl/guaiacyl ratio tends to form more cross-linkages along with higher viscosity values, higher molecular weight and larger amounts of condensed bonds.

Integrating Separation and Conversion—Conversion of Biorefinery Process Streams to Biobased Chemicals and Fuels

The concept of the integrated biorefinery is critical to developing a robust biorefining industry in the USA. Within this model, the biorefinery will produce fuel as a high-volume output addressing domestic energy needs and biobased chemical products (high-value organics) as an output providing necessary economic support for fuel production. This paper will overview recent developments within two aspects of the integrated biorefinery—the fractionation of biomass into individual process streams and the subsequent conversion of lignin into chemical products. Solvent-based separation of switchgrass, poplar, and mixed feedstocks is being developed as a biorefinery “front end” and will be described as a function of fractionation conditions. Control over the properties and structure of the individual biomass components (carbohydrates and lignin) can be observed by adjusting the fractionation process. Subsequent conversion of the lignin isolated from this fractionation leads to low molecular weight aromatics from selective chemical oxidation. Together, processes such as these provide examples of foundational technology that will contribute to a robust domestic biorefining industry.