Short‐term lime pretreatment of poplar wood

Short‐term lime pretreatment uses lime and high‐pressure oxygen to significantly increase the digestibility of poplar wood. When the treated poplar wood was enzymatically hydrolyzed, glucan and xylan were converted to glucose and xylose, respectively. To calculate product yields from raw biomass, these sugars were expressed as equivalent glucan and xylan. To recommend pretreatment conditions, the single criterion was the maximum overall glucan and xylan yields using a cellulase loading of 15 FPU/g glucan in raw biomass. On this basis, the recommended conditions for short‐term lime pretreatment of poplar wood follow: (1) 2 h, 140°C, 21.7 bar absolute and (2) 2 h, 160°C, and 14.8 bar absolute. In these two cases, the reactivity was nearly identical, thus the selected condition depends on the economic trade off between pressure and temperature. Considering glucose and xylose and their oligomers produced during 72 h of enzymatic hydrolysis, the overall yields attained under these recommended conditions follow: (1) 95.5 g glucan/100 g of glucan in raw biomass and 73.1 g xylan/100 g xylan in raw biomass and (2) 94.2 g glucan/100 g glucan in raw biomass and 73.2 g xylan/100 g xylan in raw biomass. The yields improved by increasing the enzyme loading. An optimal enzyme cocktail was identified as 67% cellulase, 12% β‐glucosidase, and 24% xylanase (mass of protein basis) with cellulase activity of 15 FPU/g glucan in raw biomass and total enzyme loading of 51 mg protein/g glucan in raw biomass. Ball milling the lime‐treated poplar wood allowed for 100% conversion of glucan in 120 h with a cellulase loading of only 10 FPU/g glucan in raw biomass. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Transformations of bioactive peptides in the presence of sugars--characterization and stability studies of the adducts generated via the Maillard reaction

Glycation of biomolecules, such as proteins, peptide hormones, nucleic acids, and lipids, may be a major contributor to the pathological manifestations of aging and diabetes mellitus. These nonenzymatic reactions, also termed the Maillard reaction, alter the biological and chemical properties of biomolecules. In order to investigate the effect of various reducing sugars on the products formed from small bioactive peptides (Tyr-Gly-Gly-Phe-Leu, Tyr-Gly-Gly-Phe-Leu-NH2, Tyr-Gly-Gly-Phe-Leu-OMe, Tyr-Gly-Gly-Phe, and Tyr-Gly-Gly), model systems were prepared with glucose, mannose or galactose. Peptide-sugar mixtures were incubated at 37 or 50 degrees C in phosphate-buffered saline, pH 7.4, or in methanol. The extent of glycation was determined periodically by RP HPLC. All sugar-peptide mixtures generated two different types of glycation products: N-(1-deoxy-ketos-1-yl)-peptide (Amadori compound) and the imidazolidinone compound substituted by sugar pentitol and peptide residue. The amount and distribution of peptide glycation products depended on the structure of the reactants, and increased in both concentration- and time-dependent manner in relation to exposure to sugar. Additionally, the rate of hydrolysis of glucose-derived imidazolidinone compounds, obtained either from leucine-enkephalin (1) or its shorter N-terminal fragments 2 and 3, was determined by incubation at 37 degrees C in human serum. These results revealed that imidazolidinones obtained from glucose and small peptides are almost completely protected from the action of enzymes in serum, the predominant route of degradation being spontaneous hydrolysis to initial sugar and peptide compound.     

Renewal ecology: conservation for the Anthropocene

The global scale and rapidity of environmental change is challenging ecologists to reimagine their theoretical principles and management practices. Increasingly, historical ecological conditions are inadequate targets for restoration ecology, geographically circumscribed nature reserves are incapable of protecting all biodiversity, and the precautionary principle applied to management interventions no longer ensures avoidance of ecological harm. In addition, human responses to global environmental changes, such as migration, building of protective infrastructures, and land use change, are having their own negative environmental impacts. We use examples from wildlands, urban, and degraded environments, as well as marine and freshwater ecosystems, to show that human adaptation responses to rapid ecological change can be explicitly designed to benefit biodiversity. This approach, which we call “renewal ecology,” is based on acceptance that environmental change will have transformative effects on coupled human and natural systems and recognizes the need to harmonize biodiversity with human infrastructure, for the benefit of both.     

Growth and carbon isotopes of Mediterranean trees reveal contrasting responses to increased carbon dioxide and drought

Forest dynamics will depend upon the physiological performance of individual tree species under more stressful conditions caused by climate change. In order to compare the idiosyncratic responses of Mediterranean tree species (Quercus faginea, Pinus nigra, Juniperus thurifera) coexisting in forests of central Spain, we evaluated the temporal changes in secondary growth (basal area increment; BAI) and intrinsic water-use efficiency (iWUE) during the last four decades, determined how coexisting species are responding to increases in atmospheric CO₂ concentrations (C _a) and drought stress, and assessed the relationship among iWUE and growth during climatically contrasting years. All species increased their iWUE (ca. +15 to +21 %) between the 1970s and the 2000s. This increase was positively related to C _a for J. thurifera and to higher C _a and drought for Q. faginea and P. nigra. During climatically favourable years the study species either increased or maintained their growth at rising iWUE, suggesting a higher CO₂ uptake. However, during unfavourable climatic years Q. faginea and especially P. nigra showed sharp declines in growth at enhanced iWUE, likely caused by a reduced stomatal conductance to save water under stressful dry conditions. In contrast, J. thurifera showed enhanced growth also during unfavourable years at increased iWUE, denoting a beneficial effect of C _a even under climatically harsh conditions. Our results reveal significant inter-specific differences in growth driven by alternative physiological responses to increasing drought stress. Thus, forest composition in the Mediterranean region might be altered due to contrasting capacities of coexisting tree species to withstand increasingly stressful conditions.     

Study of degradation pathways of Amadori compounds obtained by glycation of opioid pentapeptide and related smaller fragments: stability,reactions, and spectroscopic properties

Reactions between biological amines and reducing sugars (the Maillard reaction) are among the most important of the chemical and oxidative changes occurring in biological systems that contribute to the formation of a complex family of rearranged and dehydrated covalent adducts that have been implicated in the pathogenesis of human diseases. In this study, chemistry of the Maillard reactions was studied in four model systems containing fructosamines (Amadori compounds) obtained from the endogenous opioid pentapeptide leucine-enkephalin (Tyr-Gly-Gly-Phe-Leu), leucine-enkephalin methyl ester, structurally related tripeptide (Tyr-Gly-Gly), or from amino acid (Tyr). The degradation of model compounds as well as their ability to develop Maillard fluorescence was investigated under oxidative conditions in methanol and phosphate buffer pH 7.4 at two different temperatures (37 and 70 degrees C). At 37 degrees C, glycated leucine-enkephalin degraded slowly in methanol (t(1/2) approximately 13 days) and phosphate buffer (t(1/2) approximately 9 days), producing a parent peptide compound as a major product throughout a three-week incubation period. Whereas fluorescence slowly increased over time at 37 degrees C, incubations off all studied Amadori compounds at 70 degrees C resulted in a rapid appearance of a brown color and sharp increase in AGE (advanced glycation end products)-associated fluorescence (excitation 320 nm/emmision 420 nm) as well as in distinctly higher amounts of fragmentation products. The obtained data indicated that the shorter the peptide chain the more degradation products were formed. These studies have also helped to identify a new chemical transformation of the peptide backbone in the Maillard reaction that lead to beta-scission of N-terminal tyrosine side chain and p-hydroxybenzaldehyde formation under both aqueous and nonaqueous conditions.     

An improved description of Strombidium sulcatum Claparède & Lachmann, 1859 (Ciliophora) from slides of Fauré-Fremiet, and a designation of type material

Strombidium sulcatum, the type species of the genus, is examined using silver-stained material made by Fauré-Fremiet in the 1950s and 1960s. We found that the stained specimens possessed a prominent protuberance, as previously described; the number of anterior polykinetids (APk) differed between the accounts (15 this study, 12 previous reports); although previously illustrated, no contractile vacuole was observed; and the macronuclear shape, position, and size differed from those previously reported. Our work provides the first detailed re-analysis of the silver-stained material of S. sulcatum. We use data on S. sulcatum to distinguish it from a morphologically similar species, Strombidium inclinatum. Type material for S. sulcatum has been deposited in the Natural History Museum, London.     

Isolation and binding properties of leucyl-tRNA synthetase from Escherichia coli MRE 600

Summary A procedure for the large-scale isolation of leucyl-tRNA synthetase from E. coli MRE 600 is described: The enzyme was purified about 320-fold to homogeneity by precipitation with cetyl-trimethyl-ammonium bromide, two consecutive chromatographies on DEAE-cellulose and three on hydroxyapatite with an over-all yield of 4%.The molecular weight of leucyl-tRNA synthetase from E. coli MRE 600 was found to be 99 000 daltons. Binding studies by ultracentrifugation and equilibrium partition showed that the enzyme binds leucine, leucyl-adenylate and tRNA^Leu, each in a 1 : 1 stoichiometry. For ATP only a very weak binding to the enzyme could be observed, which did not allow the evaluation of the complex stoichiometry. The presence of ATP was not required for the binding of leucine or tRNA to leucyl-tRNA synthetase from E. coli MRE 600.     

Technical aspects of separation using aqueous two-phase systems in enzyme isolation processes.

Technical aspects of the separation of aqueous two-phase systems in a commercial separator were studied in detail. For the Gyrotester B, the smallest available separator, a flow rate of 200 ml/min and a length of the regulating screw in the outlet port of 13.5 mm were found as optimal operation parameters for the separation of a poly(ethylene glycol) (PEG)/dextran two-phase system. In the presence of cells and cell debris the characteristics of the carrier two-phase systems are changed, most notably the phase ratio. Nevertheless good separation and high throughput can be maintained up to 30% wet cell material in the complete system. Using this method the enzyme pullulanase was extracted from 6.65 kg Klebsiella pneumoniae in 88% yield in a single step in less than 2 hr. A yield of 90% was predicted for this step based upon laboratory data, indicating that the performance of the extraction and separation can be calculated with the necessary accuracy and the further scale-up of the process should be accomplished quite easily. The hydrophilic polymers Constituting the phase system will often stabilize the enzymes, So that the separation can be carried out at room temperature without extensive cooling. The method of enzyme solubilization or cell disruption is not decisive for the successful extraction of the enzymes, the only limitation being the necessity to find a suitable two-phase system where the desired product and the cells or cell debris will partition in opposite phases. This is shown for α-glucosidase from Saccharomyces carlsbergensis and three aminoacyl-tRNA-synthetases from Escherichia coli. The results obtained demonstrate that aqueous two-phase systems can be separated in commercially available separators with high capacity and efficiency. It can be expected that the advanced separation technology available from chemical engineering studies can also be used for the development of large-scale isolation processes for enzymes involving liquid–liquid partitions.     

Differential Spectral Sensitivity in the Optic Tectum and Eye of the Turtle

Light flashes of calibrated wavelength and intensity were presented to the turtle eye and electrical responses were simultaneously recorded from the cornea and the optic tectum. Spectral sensitivity curves derived from criterion-response levels showed a characteristic red-sensitive process at both sites. At high criterion levels the two curves were quite similar. At low criterion-response levels the tectum showed an enhanced blue-green process not evident in the peripheral record. The sensitivity to blue-green may correspond to previously observed behavior.     

Entrainment of circadian rhythms of cholesterol‐LDL,corticosterone and motor activity by feeding schedules in rats

Abstract

The daily variations of locomotor activity, plasma and adrenal corticosterone levels and cholesterol‐LDL were studied in male Wistar rats with food ad libitum and feeding restricted to the first 4 hours of the light phase in LD 12:12..

Under LD 12:12 (light on from 9:00 to 21:00h) rats with food ad libitum were eating and moving during the dark period and the locomotor activity clearly showed a biphasic pattern with three harmonic components. Plasma and adrenal corticosterone levels increased during the light period and reached a maximum value just before the dark period whereas the acrophase of cholesterol‐LDL is found at the beginning of the light phase.

The acrophases of activity, plasma and adrenal corticosterone levels in the restricted feeding schedule rats occurred in the first three hours of lighting and the cholesterol‐LDL acrophase at the beginning of the dark phase.

These results confirm a previous report that the shift of feeding to the light phase seems to cause a concomitant phase‐shift in all the variables measured.