ABE Fermentation From Low Cost Substrates

The high cost of substrate and product inhibition in the fermentation broth remains two major problems associated with bio-butanol production. This thesis aims to solve these problems by examining abundant lignocellulosic biomass as potential feedstocks and exploring novel substrates such as carbohydrates derived from microalgae for ABE fermentation. The commonly observed toxic effect after pretreatment of lignocelluslosic biomass was removed by resin adsorption, where the resin could also serve as an in-situ butanol recvoery devices. Corn cobs (an agricultural waste), switchgrass (an energy crop) and phragmites (an invasive plant in North America) were investigated as substrates for ABE fermentation by Clostridium saccharobutylicum DSM 13864. NaOH pretreatment followed by a washing step was used to reduce the biomass recalcitrance and facilitate the subsequent enzymatic hydrolysis. Total sugar yields for corn cobs, switchgrass and phragmites were 475, 365, and 385 g/kg of raw biomass, respectively. After the subsequent fermentation, an ABE yield of 166, 146, and 150 g/kg raw biomass was obtained. Although biofuel production from lignocellulosic biomass is considered more sustainable than biofuel from food crops, it still faces many challenges. In order to demonstrate a possible biofuel production strategy using microalgal biomass, lipid extracted microalgae (LEA) was also used as substrates for ABE fermentation. To convert the carbohydrate fraction into solvents (ABE), LEA was either acid hydrolysed into glucose or directly fermented. The highest butanol titers (8.05 g/L) was obtained with the fermentation of acid hydrolysates. However fermenting the hydrolysate required detoxification via a resin, while direct fermentation did not, significantly simplifying the LEA to butanol process. The resin that was used to detoxify acid hydrolysates of LEA was further investigated for detoxification of lignocellulosic hydrolysates and in-situ butanol recovery. Detoxifcation of acid hydrolyzed phragmites by resin L-493, improved the fermentability signficantly. Resin L-493 was efficient in removing phenolic comopunds present in the phragmites hydrolysates, as well as butanol produced during fermentation

Study on Cement Slurry System for Deep and Ultra-Deep Wells

Cementing quality can’t meet the requirements in deep and ultra-deep wells cementing because of many factors such as long open hole section, multiple pressure system, high temperature and high pressure. In order to solve the problem of cementing in deep and ultra-deep wells, retarder and fluid loss additive were studied, then the cement slurry system for deep and ultra-deep wells were developed and the performance was evaluated. The results show that the cement slurry has steady performance for high temperature, adjustable thickening time, less fluid loss, good settlement stability, and high compressive strength, all of which can meet the requirement of cementing in deep and ultra-deep wells. Pilot tests of this cement system were conducted in more than 30 wells in Shengli, Dagang, Liaohe, Jiangsu, Jilin and Offshore oilfield, cementing qualities of these wells were qualified, which indicates that comprehensive performance of this kind of cement slurry system can meet the technical requirements for deep and ultra-deep wells cementing, which provides the references for the deep and ultra-deep wells cementing in all of the word.Key words: Deep and ultra-deep wells; Cementing; Fluid loss additive; Retarder; Thickening tim

Multiscale Method for Elastic Wave Propagation in the Heterogeneous, Anisotropic Media

Seismic wave simulation in realistic Earth media with full wavefield methods is a fundamental task in geophysical studies. Conventional approaches such as the finite-difference method and the finite-element method solve the wave equation in geological models represented with discrete grids and elements. When the Earth model includes complex heterogeneities at multiple spatial scales, the simulation requires fine discretization and therefore a system with many degrees of freedom, which often exceeds current computational abilities. In this dissertation, I address this problem by proposing new multiscale methods for simulating elastic wave propagation based on previously developed algorithms for solving the elliptic partial differential equations and the acoustic wave equation. The fundamental motivation for developing the multiscale method is that it can solve the wave equation on a coarsely discretized mesh by incorporating the effects of fine-scale medium properties using so-called multiscale basis functions. This can greatly reduce computation time and degrees of freedom compared with conventional methods. I first derive a numerical homogenization method for arbitrarily heterogeneous, anisotropic media that utilizes the multiscale basis functions determined from a local linear elasticity equation to compute effective, anisotropic properties, and these equivalent elastic medium parameters can be used directly in existing elastic modeling algorithms. Then I extend the approach by constructing multiple basis functions using two types of appropriately defined local spectral linear elasticity problems. Given the eigenfunctions determined from local spectral problems, I develop a generalized multiscale finite-element method (GMsFEM) for elastic wave propagation in heterogeneous, anisotropic media in both continuous Galerkin (CG) and discontinuous Galerkin (DG) formulations. The advantage of the multiscale basis functions is they are model-dependent, unlike the predefined polynomial basis functions applied in conventional finite-element methods. For this reason, the GMsFEM can effectively capture the influence of fine-scale variation of the media. I present results for several numerical experiments to verify the effectiveness of both the numerical homogenization method and GMsFEM. These tests show that the effectiveness of the multiscale method relies on the appropriate choice of boundary conditions that are applied for the local problem in numerical homogenization method and on the selection of basis functions from a large set of eigenfunctions contained in local spectral problems in GMsFEM. I develop methods for solving both these problems, and the results confirm that the multiscale method can be powerful tool for providing accurate full wavefield solutions in heterogeneous, anisotropic media, yet with reduced computation time and degrees of freedom compared with conventional full wavefield modeling methods. Specially, I applied the DG-GMsFEM to the Marmousi-2 elastic model, and find that DG-GMsFEM can greatly reduce the computation time compared with continuous Galerkin (CG) FEM

Structure-based drug discovery aiming at human-diseases related protein targets

Drug discovery remains a challenging task in both academic research and the pharmaceutical industry, owning to the fast upgrades to existing methods and the development of new methods that are applied in this field combined with the growing knowledge of disease mechanism from molecular biology. The speed with which a valuable new drug can be found and continue to use in clinics has accelerated rapidly compared to centuries ago. This thesis mainly focuses on the early stage of drug discovery aiming at human-diseases related protein targets. Four target proteins are introduced: PfPdxK kinase a protein related to malaria infections, human acute leukemia associated protein Menin and two human arginases involved in cancer. To investigate the interactions between proteins and ligands, we searched for and designed specific peptides, small fragments, or larger compounds to modulate or inhibit the protein targets. The designs were in part based on information gained from protein structures obtained by X-ray diffraction studies and we used fragment-based drug discovery and high throughput screening to screen large compound libraries to discover new binding compounds. Multiple biophysical approaches were used to validate the hits that were found, including differential scanning fluorimetry, microscale thermophoresis, and surface plasmon resonance. These techniques confirmed the hits found from screening and therefore provide a good start for fragment or compound growth index based improvement of the hits and later lead-like compounds optimization in future research