Pretreatment and fractionation of lignocellulosic biomass for production of biofuel and value-added products

Biorefineries are sustainable biomass conversion processes to make bio-based fuels and chemical products. In this thesis, several different lignocellulosic biomass pretreatment and fractionation processes are developed and described with possible biorefinery applications. Fractionation using aqueous ammonia and hot-water, hybrid fractionation using zinc chloride (ZnCl2) and simultaneous saccharification and fermentation (SSF), low-moisture anhydrous ammonia pretreatment, and photocatalyst-assisted ammonia pretreatment are investigated to improve the utilization of lignocellulosic biomass. The two-stage fractionation process using aqueous ammonia and hot-water separated three main components with relatively high purity of each component. Ammonia treatment selectively removed lignin from biomass, while hot-water treatment separately hydrolyzed hemicellulose in the following stage. Under the optimal reaction conditions using RSM, relatively high purity of hemicellulose and lignin were recovered. High enzymatic digestibility and fermentability were also resulted with cellulose fraction. A hybrid fractionation process using ZnCl2 and SSF was also investigated to improve the utilization of lignocellulosic biomass. The ZnCl2 showed high swelling effect and selectivity for hemicellulose; hence most of the hemicellulose was released into the liquid hydrolysate by ZnCl2 treatment. The fractionated hemicellulose in the liquid hydrolysates was converted into furfural by thermal reaction, while the residual solids which have high cellulose and lignin contents were converted into ethanol by SSF. Up to 98% of theoretical maximum ethanol yield was obtained; therefore, the residual solids could be high purity lignin. Low-moisture anhydrous ammonia pretreatment was studied in an effort to minimize ammonia and water input and to obtain high enzymatic digestibilities and ethanol yield. Gaseous ammonia treatment significantly reduced ammonia input (0.1 g ammonia/g biomass) and water input (1.0 g water/g biomass). In addition, there was no washing step which required significant washing water. Even though water and ammonia inputs were significantly reduced compared to previous ammonia pretreatment methods, the maximum theoretical ethanol yield (based on glucan and xylan in the biomass) reached 90% by simultaneous saccharification and cofermentation (SSCF). A photocatalyst-assisted ammonia pretreatment method was developed to enhance the effects of liquid ammonia pretreatment by oxidation reaction with photocatalysts. Higher delignification and enzymatic hydrolysis yield of treated solids resulted from photocatalyst-assisted ammonia pretreatment compared to ammonia pretreatment itself. Moreover, photocatalysts shortened the pretreatment time. Improving the pretreatment effects and shortening the pretreatment time by UV treatment using photocatalysts show a potential of photocatalytic treatment as a useful technology for lignocellulosic biomass utilization. These studies show that the development of biomass conversion process can contribute to the utilization of lignocellulosic biomass. Each approach has its own particular solution to the problems of biomass conversion processes. Fractionation processes propose ways to produce valuable building blocks, and pretreatment processes suggest efficient methods by enhancing conversion yields and reducing production costs. Although there are still many obstacles to overcome, these studies are believed to help commercialize lignocellulosic biomass products

Optimal Initial Perturbations for Ensemble Prediction of the Madden-Julian Oscillation during Boreal Winter

An initialization strategy, tailored to the prediction of the Madden-Julian oscillation (MJO), is evaluated using the Goddard Earth Observing System Model, version 5 (GEOS-5), coupled general circulation model (CGCM). The approach is based on the empirical singular vectors (ESVs) of a reduced-space statistically determined linear approximation of the full nonlinear CGCM. The initial ESV, extracted using 10 years (1990-99) of boreal winter hindcast data, has zonal wind anomalies over the western Indian Ocean, while the final ESV (at a forecast lead time of 10 days) reflects a propagation of the zonal wind anomalies to the east over the Maritime Continent an evolution that is characteristic of the MJO. A new set of ensemble hindcasts are produced for the boreal winter season from 1990 to 1999 in which the leading ESV provides the initial perturbations. The results are compared with those from a set of control hindcasts generated using random perturbations. It is shown that the ESV-based predictions have a systematically higher bivariate correlation skill in predicting the MJO compared to those using the random perturbations. Furthermore, the improvement in the skill depends on the phase of the MJO. The ESV is particularly effective in increasing the forecast skill during those phases of the MJO in which the control has low skill (with correlations increasing by as much as 0.2 at 20 25-day lead times), as well as during those times in which the MJO is weak

Deep Eutectic Solvent Pretreatment of Transgenic Biomass With Increased C6C1 Lignin Monomers.

The complex and heterogeneous polyphenolic structure of lignin confers recalcitrance to plant cell walls and challenges biomass processing for agroindustrial applications. Recently, significant efforts have been made to alter lignin composition to overcome its inherent intractability. In this work, to overcome technical difficulties related to biomass recalcitrance, we report an integrated strategy combining biomass genetic engineering with a pretreatment using a bio-derived deep eutectic solvent (DES). In particular, we employed biomass from an Arabidopsis line that expressed a bacterial hydroxycinnamoyl-CoA hydratase-lyase (HCHL) in lignifying tissues, which results in the accumulation of unusual C6C1 lignin monomers and a slight decrease in lignin molecular weight. The transgenic biomass was pretreated with renewable DES that can be synthesized from lignin-derived phenols. Biomass from the HCHL plant line containing C6C1 monomers showed increased pretreatment efficiency and released more fermentable sugars up to 34% compared to WT biomass. The enhanced biomass saccharification of the HCHL line is likely due to a reduction of lignin recalcitrance caused by the overproduction of C6C1 aromatics that act as degree of polymerization (DP) reducers and higher chemical reactivity of lignin structures with such C6C1 aromatics. Overall, our findings demonstrate that strategic plant genetic engineering, along with renewable DES pretreatment, could enable the development of sustainable biorefinery

Double-Well Potential : The WKB Approximation with Phase Loss and Anharmonicity Effect

We derive a general WKB energy splitting formula in a double-well potential by incorporating both phase loss and anharmonicity effect in the usual WKB approximation. A bare application of the phase loss approach to the usual WKB method gives better results only for large separation between two potential minima. In the range of substantial tunneling, however, the phase loss approach with anharmonicity effect considered leads to a great improvement on the accuracy of the WKB approximation.Comment: 14 pages, revtex, 1 figure, will appear at Phys. Rev.

Visualization of lignification in flax stem cell walls with novel click-compatible monolignol analogs

IntroductionAs an essential part of plant cell walls, lignin provides mechanical support for plant growth, enhances water transport, and helps to defend against pathogens. As the most abundant natural aromatic-based renewable resource on earth, its biosynthesis has always been a research focus, and it is still currently under study.MethodsIn this study, the p-coumaryl alcohol analog (HALK) and the coniferyl alcohol analog (GALK) containing an alkyne group at the ortho position were synthesized and applied to lignification in vivo and in vitro. The incorporation of these novel lignin monomers was observed via fluorescence imaging.Results and DiscussionIt was found that the two monolignol analogs could be incorporated in dehydrogenated polymers (DHPs) in vitro and in flax cell walls in vivo. The results showed that as the cultivation time and precursor concentration varied, the deposition of H and G-type lignin exhibited differences in deposition mode. At the subcellular scale, the deposited lignin first appears in the cell corner and the middle lamella, and then gradually appears on the cell walls. Furthermore, lignin was also found in bast fiber. It was demonstrated that these new molecules could provide high-resolution localization of lignin during polymerization

Combining loss of function of FOLYLPOLYGLUTAMATE SYNTHETASE1 and CAFFEOYL-COA 3-O-METHYLTRANSFERASE1 for lignin reduction and improved saccharification efficiency in Arabidopsis thaliana

This article tests if lignin content can be further reduced by combining genetic mutations in C1 metabolism and the lignin biosynthetic pathway by generating and functionally characterizing fpgs1ccoaomt1 double mutants. The observations demonstrate that additional reduction in lignin content and improved sugar release can be achieved by simultaneous downregulation of a gene in the C1 (FPGS1) and lignin biosynthetic (CCOAOMT) pathways