Identification of a haloalkaliphilic and thermostable cellulase with improved ionic liquid tolerance (open access)

Identification of a haloalkaliphilic and thermostable cellulase with improved ionic liquid tolerance

Some ionic liquids (ILs) have been shown to be very effective solvents for biomass pretreatment. It is known that some ILs can have a strong inhibitory effect on fungal cellulases, making the digestion of cellulose inefficient in the presence of ILs. The identification of IL-tolerant enzymes that could be produced as a cellulase cocktail would reduce the costs and water use requirements of the IL pretreatment process. Due to their adaptation to high salinity environments, halophilic enzymes are hypothesized to be good candidates for screening and identifying IL-resistant cellulases. Using a genome-based approach, we have identified and characterized a halophilic cellulase (Hu-CBH1) from the halophilic archaeon, Halorhabdus utahensis. Hu-CBH1 is present in a gene cluster containing multiple putative cellulolytic enzymes. Sequence and theoretical structure analysis indicate that Hu-CBH1 is highly enriched with negatively charged acidic amino acids on the surface, which may form a solvation shell that may stabilize the enzyme, through interaction with salt ions and/or water molecules. Hu-CBH1 is a heat tolerant haloalkaliphilic cellulase and is active in salt concentrations up to 5 M NaCl. In high salt buffer, Hu-CBH1 can tolerate alkali (pH 11.5) conditions and, more importantly, is tolerant to high levels (20percent w/w) of ILs, …
Date: February 17, 2011
Creator: Zhang, Tao; Datta, Supratim; Eichler, Jerry; Ivanova, Natalia; Axen, Seth D.; Kerfeld, Cheryl A. et al.
System: The UNT Digital Library
High Resolution Simulations of Ignition Capsule Designs for the National Ignition Facility (open access)

High Resolution Simulations of Ignition Capsule Designs for the National Ignition Facility

Ignition capsule designs for the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 443, 2841 (2004)] have continued to evolve in light of improved physical data inputs, improving simulation techniques, and - most recently - experimental data from a growing number of NIF sub-ignition experiments. This paper summarizes a number of recent changes to the cryogenic capsule design and some of our latest techniques in simulating its performance. Specifically, recent experimental results indicated harder x-ray drive spectra in NIF hohlraums than were predicted and used in previous capsule optimization studies. To accommodate this harder drive spectrum, a series of high-resolution 2-D simulations, resolving Legendre mode numbers as high as two thousand, were run and the germanium dopant concentration and ablator shell thicknesses re-optimized accordingly. Simultaneously, the possibility of cooperative or nonlinear interaction between neighboring ablator surface defects has motivated a series of fully 3-D simulations run with the massively parallel HYDRA code. These last simulations include perturbations seeded on all capsule interfaces and can use actual measured shell surfaces as initial conditions. 3-D simulations resolving Legendre modes up to two hundred on large capsule sectors have run through ignition and burn, and …
Date: February 17, 2011
Creator: Clark, D. S.; Haan, S. W.; Cook, A. W.; Edwards, M. J.; Hammel, B. A.; Koning, J. M. et al.
System: The UNT Digital Library
Archaeological Protein Residues: New Data for Conservation Science (open access)

Archaeological Protein Residues: New Data for Conservation Science

This article identifies several cases where archaeological protein residues may be of benefit, justifies the use of protein residues in particular, and discusses areas for improvement.
Date: February 17, 2011
Creator: Barker, Andrew
System: The UNT Digital Library