Browsing by Author "Virginia Tech. Department of Biological Systems Engineering"
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- Evaluating the effectiveness of best management practices with a rainfall simulatorVirginia Tech. Department of Biological Systems Engineering (2007-01-05)Runoff plot studies utilizing a rainfall simulator at Policy Fork Research Facility near Blacksburg. Researchers are evaluating the water quality impacts of various land management practices with respect to sediment and nutrient losses.
- Genetically Encoded Self-Assembly of Large Amyloid FibersRidgley, Devin M.; Freedman, Benjamin G.; Lee, Parker W.; Barone, Justin R. (The Royal Society of Chemistry, 2014-01-14)“Functional” amyloids are found throughout nature as robust materials. We have discovered that “template” and “adder” proteins cooperatively self-assemble into micrometer-sized amyloid fibers with a controllable, hierarchical structure. Here, Escherichia coli is genetically engineered to express a template protein, Gd20, that can initiate self-assembly of large amyloid fibrils and fibers. Through atomic force microscopy (AFM) we found that expression of Gd20 produces large amyloid fibrils of 490 nm diameter and 2–15 _m length. Addition of an extracellular adder protein, myoglobin, continues self-assembly to form amyloid tapes with widths of [similar]7.5 _m, heights of [similar]400 nm, and lengths exceeding 100 _m. Without myoglobin the amyloid fibrils are metastable over time. When myoglobin is present, the amyloid fiber continues self-assembling to a width of [similar]18 _m and height of [similar]1 _m. Experimental results demonstrate that large amyloid fibers with a tailored stiffness and morphology can be engineered at the DNA level, spanning four orders of magnitude.
- High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic PathwayZhang, Y. H. Percival; Evans, Barbara R.; Mielenz, Jonathan R.; Hopkins, Robert C.; Adams, Michael W. W. (2007-05-23)Background. The future hydrogen economy offers a compelling energy vision, but there are four main obstacles: hydrogen production, storage, and distribution, as well as fuel cells. Hydrogen production from inexpensive abundant renewable biomass can produce cheaper hydrogen, decrease reliance on fossil fuels, and achieve zero net greenhouse gas emissions, but current chemical and biological means suffer from low hydrogen yields and/or severe reaction conditions. Methodology/Principal Findings. Here we demonstrate a synthetic enzymatic pathway consisting of 13 enzymes for producing hydrogen from starch and water. The stoichiometric reaction is C₆H₁₀O₅ (l)+7 H₂O (l)-> 12 H₂ (g)+ 6 CO₂ (g). The overall process is spontaneous and unidirectional because of a negative Gibbs free energy and separation of the gaseous products with the aqueous reactants. Conclusions. Enzymatic hydrogen production from starch and water mediated by 13 enzymes occurred at 30 degrees C as expected, and the hydrogen yields were much higher than the theoretical limit (4 H(2)/glucose) of anaerobic fermentations. Significance. The unique features, such as mild reaction conditions (30 degrees C and atmospheric pressure), high hydrogen yields, likely low production costs ($~ to 2/kg H₂), and a high energy-density carrier starch (14.8 H₂-based mass%), provide great potential for mobile applications. With technology improvements and integration with fuel cells, this technology also solves the challenges associated with hydrogen storage, distribution, and infrastructure in the hydrogen economy.
- Metabolic Engineering of Yeast to Produce Fatty Acid-derived Biofuels: Bottlenecks and SolutionsSheng, Jiayuan; Feng, Xueyang (Frontiers, 2015-06-08)Fatty acid-derived biofuels can be a better solution than bioethanol to replace petroleum fuel, since they have similar energy content and combustion properties as current transportation fuels. The environmentally friendly microbial fermentation process has been used to synthesize advanced biofuels from renewable feedstock. Due to their robustness as well as the high tolerance to fermentation inhibitors and phage contamination, yeast strains such as Saccharomyces cerevisiae and Yarrowia lipolytica have attracted tremendous attention in recent studies regarding the production of fatty acid-derived biofuels, including fatty acids, fatty acid ethyl esters, fatty alcohols, and fatty alkanes. However, the native yeast strains cannot produce fatty acids and fatty acid-derived biofuels in large quantities. To this end, we have summarized recent publications in this review on metabolic engineering of yeast strains to improve the production of fatty acid-derived biofuels, identified the bottlenecks that limit the productivity of biofuels, and categorized the appropriate approaches to overcome these obstacles.
- Molecular basis of 5-hydroxytryptophan synthesis in Saccharomyces cerevisiaeZhang, Jiantao; Wu, Chaochen; Sheng, Jiayuan; Feng, Xueyang (Royal Society of Chemistry, 2016-03-18)We report for the first time that 5-hydroxytryptophan can be synthesized in Saccharomyces cerevisiae by heterologously expressing prokaryotic phenylalanine 4-hydroxylase or eukaryotic tryptophan 3/5-hydroxylase, together with enhanced synthesis of MH4 or BH4 cofactors. The innate DFR1 gene in the folate synthesis pathway was found to play pivotal roles in 5-hydroxytryptophan synthesis.
- Near-Real-Time Analysis of the Phenotypic Responses of Escherichia coli to 1-Butanol Exposure Using Raman SpectroscopyZu, Theresah N. K.; Athamneh, Ahmad I. M.; Wallace, Robert S.; Collakova, Eva; Senger, Ryan S. (American Society for Microbiology, 2014-08-25)Raman spectroscopy was used to study the time course of phenotypic responses of Escherichia coli (DH5 alpha) to 1-butanol exposure (1.2% [vol/vol]). Raman spectroscopy is of interest for bacterial phenotyping because it can be performed (i) in near real time, (ii) with minimal sample preparation (label-free), and (iii) with minimal spectral interference from water. Traditional offline analytical methodologies were applied to both 1-butanol-treated and control cells to draw correlations with Raman data. Here, distinct sets of Raman bands are presented that characterize phenotypic traits of E. coli with maximized correlation to offline measurements. In addition, the observed time course phenotypic responses of E. coli to 1.2% (vol/vol) 1-butanol exposure included the following: (i) decreased saturated fatty acids levels, (ii) retention of unsaturated fatty acids and low levels of cyclopropane fatty acids, (iii) increased membrane fluidity following the initial response of increased rigidity, and (iv) no changes in total protein content or protein-derived amino acid composition. For most phenotypic traits, correlation coefficients between Raman spectroscopy and traditional off-line analytical approaches exceeded 0.75, and major trends were captured. The results suggest that near-real-time Raman spectroscopy is suitable for approximating metabolic and physiological phenotyping of bacterial cells subjected to toxic environmental conditions.
- Recyclable Cellulose-Containing Magnetic Nanoparticles: Immobilization of Cellulose-Binding Module-Tagged Proteins and Synthetic Metabolon Featuring Substrate ChannelingMyung, Suwan; You, Chun; Zhang, Y. H. Percival (The Royal Society of Chemistry, 2013-07-01)Easily recyclable cellulose-containing magnetic nanoparticles were developed for immobilizing family 3 cellulose-binding module (CBM)-tagged enzymes/proteins and a self-assembled three-enzyme complex called the synthetic metabolon. Avicel (microcrystalline cellulose)-containing magnetic nanoparticles (A-MNPs) and two controls of dextran-containing magnetic nanoparticles (D-MNPs) and magnetic nanoparticles (MNPs) were prepared by a solvothermal method. Their adsorption ability was investigated by using CBM-tagged green fluorescence protein and phosphoglucose isomerase. A-MNPs had higher adsorption capacity and tighter binding on CBM-tagged proteins than the two control MNPs because of the high-affinity adsorption of CBM on cellulose. In addition, A-MNPs were used to purify and co-immobilize a three-enzyme metabolon through a CBM-tagged scaffoldin containing three different cohesins. The three-enzyme metabolon comprised of dockerin-containing triosephosphate isomerase, aldolase, and fructose 1,6-bisphosphatase was self-assembled because of the high-affinity interaction between cohesins and dockerins. Thanks to spatial organization of the three-enzyme metabolon on the surface of A-MNPs, the metabolon exhibited a 4.6 times higher initial reaction rate than the non-complexed three-enzyme mixture at the same enzyme loading. These results suggested that the cellulose-containing MNPs were new supports for immobilizing enzymes, which could be selectively recycled or removed from other biocatalysts by a magnetic force, and the use of enzymes immobilized on A-MNPs could be very useful to control the On/Off process in enzymatic cascade reactions.
- Upper Stroubles Creek Watershed TMDL Implementation Plan Montgomery County, VirginiaStroubles Creek IP Steering Committee; Virginia Tech. Department of Biological Systems Engineering; Virginia Water Resources Research Center (Virginia Tech, 2006-05-24)A Total Maximum Daily Load (TMDL) study was conducted on Stroubles Creek from April 2002 through October 2003 and approved by EPA in January 2004 (Benham et al., 2003). The TMDL specified the maximum sediment load that Stroubles Creek can handle in a manner that is protective of the habitat for benthic macroinvertebrates, in particular, and aquatic life, in general, so that it is in compliance with Virginia water quality standards. This document serves as the Total Maximum Daily Load (TMDL) implementation plan (IP) for Stroubles Creek in Montgomery County and the Town of Blacksburg, Virginia. The implementation plan is the next step in the TMDL process that specifies where and how the sediment reductions called for in the TMDL study will be made to remove the benthic impairment on Stroubles Creek.