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61.
Enzyme hydrolysis and ethanol fermentation of liquid hot water and AFEX pretreated distillers' grains at high-solids loadings 总被引:1,自引:0,他引:1
Kim Y Hendrickson R Mosier NS Ladisch MR Bals B Balan V Dale BE 《Bioresource technology》2008,99(12):5206-5215
The dry milling ethanol industry produces distiller's grains as major co-products, which are composed of unhydrolyzed and unfermented polymeric sugars. Utilization of the distiller's grains as an additional source of fermentable sugars has the potential to increase overall ethanol yields in current dry grind processes. In this study, controlled pH liquid hot water pretreatment (LHW) and ammonia fiber expansion (AFEX) treatment have been applied to enhance enzymatic digestibility of the distiller's grains. Both pretreatment methods significantly increased the hydrolysis rate of distiller's dried grains with solubles (DDGS) over unpretreated material, resulting in 90% cellulose conversion to glucose within 24h of hydrolysis at an enzyme loading of 15FPU cellulase and 40 IU beta-glucosidase per gram of glucan and a solids loading of 5% DDGS. Hydrolysis of the pretreated wet distiller's grains at 13-15% (wt of dry distiller's grains per wt of total mixture) solids loading at the same enzyme reduced cellulose conversion to 70% and increased conversion time to 72h for both LHW and AFEX pretreatments. However, when the cellulase was supplemented with xylanase and feruloyl esterase, the pretreated wet distiller's grains at 15% or 20% solids (w/w) gave 80% glucose and 50% xylose yields. The rationale for supplementation of cellulases with non-cellulolytic enzymes is given by Dien et al., later in this journal volume. Fermentation of the hydrolyzed wet distiller's grains by glucose fermenting Saccharomyces cerevisiae ATCC 4124 strain resulted in 100% theoretical ethanol yields for both LHW and AFEX pretreated wet distiller's grains. The solids remaining after fermentation had significantly higher protein content and are representative of a protein-enhanced wet DG that would result in enhanced DDGS. Enhanced DDGS refers to the solid product of a modified dry grind process in which the distiller's grains are recycled and processed further to extract the unutilized polymeric sugars. Compositional changes of the laboratory generated enhanced DDGS are also presented and discussed. 相似文献
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Differential Roles of the Pseudomonas aeruginosa PA14 rpoN Gene in Pathogenicity in Plants, Nematodes, Insects, and Mice 总被引:3,自引:0,他引:3 下载免费PDF全文
Erik L. Hendrickson Joulia Plotnikova Shalina Mahajan-Miklos Laurence G. Rahme Frederick M. Ausubel 《Journal of bacteriology》2001,183(24):7126-7134
We cloned the rpoN (ntrA, glnF) gene encoding the alternate sigma factor sigma(54) from the opportunistic multihost pathogen Pseudomonas aeruginosa strain PA14. A marker exchange protocol was used to construct the PA14 rpoN insertional mutation rpoN::Gen(r). PA14 rpoN::Gen(r) synthesized reduced levels of pyocyanin and displayed a variety of phenotypes typical of rpoN mutants, including a lack of motility and the failure to grow on nitrate, glutamate, or histidine as the sole nitrogen source. Compared to wild-type PA14, rpoN::Gen(r) was ca. 100-fold less virulent in a mouse thermal injury model and was significantly impaired in its ability to kill the nematode Caenorhabditis elegans. In an Arabidopsis thaliana leaf infectivity assay, although rpoN::Gen(r) exhibited significantly reduced attachment to trichomes, stomata, and the epidermal cell surface, did not attach perpendicularly to or perforate mesophyll cell walls, and proliferated less rapidly in Arabidopsis leaves, it nevertheless elicited similar disease symptoms to wild-type P. aeruginosa PA14 at later stages of infection. rpoN::Gen(r) was not impaired in virulence in a Galleria mellonella (greater wax moth) pathogenicity model. These data indicate that rpoN does not regulate the expression of any genes that encode virulence factors universally required for P. aeruginosa pathogenicity in diverse hosts. 相似文献
64.
Erythrocruorins are giant extracellular respiratory proteins found freely dissolved in the blood of annelids. We present here results from our ultracentrifugation, electron microscopy, spectroscopy, and diffraction experiments on these erythrocruorins. These data are rationalized in terms of a three-dimensional model of the quaternary structure. The proposed structure is arranged in a hierarchy of symmetry. The implications of this structure for the assembly process are considered with special attention to uniqueness and self-limitation. The hypothesis is consistent with observations not used in its construction and it serves as a working hypothesis to focus further experimentation. 相似文献
65.
Removal of visual cortex in the rat axotomizes projection neurons in the dorsal lateral geniculate nucleus (dLGN), leading to cytological and structural changes and apoptosis. Biotinylated dextran amine was injected into the visual cortex to label dLGN projection neurons retrogradely prior to removing the cortex in order to quantify the changes in the dendritic morphology of these neurons that precede cell death. At 12 hours after axotomy we observed a loss of appendages and the formation of varicosities in the dendrites of projection neurons. During the next 7 days, the total number of dendrites and the cross-sectional areas of the dendritic arbors of projection neurons declined to about 40% and 20% of normal, respectively. The response of dLGN projection neurons to axotomy was asynchronous, but the sequence of structural changes in individual neurons was similar; namely, disruption of dendrites began within hours followed by cell soma atrophy and nuclear condensation that commenced after the loss of secondary dendrites had occurred. However, a single administration of fibroblast growth factor-2 (FGF2), which mitigates injury-induced neuronal cell death in the dLGN when given at the time of axotomy, markedly reduced the dendritic degeneration of projection neurons. At 3 and 7 days after axotomy the number of surviving dendrites of dLGN projection neurons in FGF-2 treated rats was approximately 50% greater than in untreated rats, and the cross-sectional areas of dendritic arbors were approximately 60% and 50% larger. Caspase-3 activity in axotomized dLGN projection neurons was determined by immunostaining for fractin (fractin-IR), an actin cleavage product produced exclusively by activated caspase-3. Fractin-IR was seen in some dLGN projection neurons at 36 hours survival, and it increased slightly by 3 days. A marked increase in reactivity was seen by 7 days, with the entire dLGN filled with dense fractin-IR in neuronal cell somas and dendrites. 相似文献
66.
C Cappadona E M Redmond N G Theodorakis I H McKillop R Hendrickson A Chhabra J V Sitzmann P A Cahill 《Experimental cell research》1999,250(1):174-186
The objective of this study was to determine the effect of phenotype on pulse pressure-induced signaling and growth of vascular smooth muscle cells in vitro. Using a perfused transcapillary culture system, cells were exposed to increases in pulsatile flow and hence pulse pressure and maintained for 72 h before cells were harvested. Cell proliferation was determined by cell number, DNA synthesis, and proliferating cell nuclear antigen expression. Mitogen-activated protein kinase (MAPK) levels were determined by immunoblot and kinase activity by phosphorylation of myelin basic protein. Cell phenotype was determined by immunoblot and immunocytofluorescence using antisera specific for the differentiation markers alpha-actin, myosin, calponin, osteopontin, and phospholamban. In cells that highly expressed these differentiation markers, there was a significant increase in cell growth in response to chronic increases in pulse pressure without a significant change in MAPK activity in these cells. In contrast, in cells that weakly expressed SMC differentiation markers, there was a significant decrease in cell growth concomitant with a significant decrease in MAPK signaling in these cells. We conclude that SMC phenotype dictates the growth response of SMC to mechanical force in vitro. 相似文献
67.
The AIDS era has seen multiple advances in the power of genetics research; scores of host genetic protective factors have been nominated and several have translated to the bedside. We discuss how genomics may inform HIV/AIDS prevention, treatment and eradication. 相似文献
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69.
Crystals of myohemerythrin 总被引:1,自引:0,他引:1
Crystals have been grown of metazide myohemerythrin from the sipunculid Dendrostomum pyroides. The crystals are in space group P212121 and have unit cell dimensions of . An asymmetric unit contains a single myohemerythrin molecule. 相似文献
70.