bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of medium composition for lipase production byCandida rugosaNCIM 3462 using response surface methodology
Authors: Rajendran Aravindan , Thangavelu Viruthagiri 
Published: July 2007

A sequential optimization approach using statistical design of experiments was employed to enhance the lipase production by Candida rugosa in submerged batch fermentation. Twelve medium components were evaluated initially using the Plackett–Burman 2-level factorial design. The significant variables affecting lipase production were found to be glucose, olive oil, peptone, (NH4)2SO4, and FeCl3·6H2O. Various vegetable oils were tested in the second step, and among them, groundnut oil was found to be the best inducer for lipase production by C. rugosa. The third step was to identify the optimal values of the significant medium components with groundnut oil as the inducer using response surface methodology. The regression equation obtained from the experimental data designed using a central composite design was solved, and analyzing the response surface contour plots, the optimal concentrations of the significant variables were determined. A maximum lipase activity of 5.95 U·mL–1, which is 1.64 times the maximum activity obtained in the Plackett–Burman experimental trials, was observed. The optimum combination of medium constituents contained 19.604 g·L–1glucose, 13.065 mL·L–1groundnut oil, 7.473 g·L–1peptone, 0.962 g·L–1(NH4)2SO4, 0.0019 g·L–1FeCl3·6H2O, and other insignificant components at the fixed level. A predictive model of the combined effects of the independent variables using response surface methodology and an artificial neural network was proposed. The unstructured kinetic models, logistic model, and Luedeking–Piret model were used to describe cell mass and lipase production. The parameters of the models were evaluated and the lipase production by C. rugosa was found to be growth associated.
Effect of protease mutations on the production of xylanases in Streptomyces lividans
Authors: Arias Éliana , Li Haiming , Morosoli Rolf 
Published: July 2007

Three protease mutants — 7 (tap–), 12 (tap–, ssp–), and 17 (multiple mutations) — of Streptomyces lividans were tested for their influence on protein secretion. Streptomyces lividans grown in xylan secretes 3 xylanases (A, B, and C). Xylanases A (XlnA) and B (XlnB) are secreted by the Sec pathway, whereas xylanase C (XlnC) is secreted by the Tat pathway. The production of XlnA and XlnC was affected in the mutants, suggesting that the mutations interfered with both Sec- and Tat-secretion systems. However, the processing rate for the Sec and Tat precursor was similar to the wild-type strain, indicating that the mutations had no direct effect on secretion. Streptomyces lividans naturally produced 2 forms of XlnB: XlnB1, which contains the catalytic and the xylan-binding domains, and XlnB2, which contains the catalytic domain only. There was no change from the wild-type strain in the ratio of XlnB1/XlnB2 produced by the mutants, indicating that these proteases are not involved in this process. Although XlnA1, partially truncated in its xylan-binding domain, was rapidly degraded to its catalytic domain (XlnA2) in the wild-type strain, the rate of conversion was reduced in the 3 mutants, indicating that the proteases participated to some extent in this proteolytic process.
Metabolism of fatty acid in yeast: addition of reducing agents to the reaction medium influences β-oxidation activities, γ-decalactone production, and cell ultrastructure inSporidiobolus ruineniicultivated on ricinoleic acid methyl ester
Authors: Feron Gilles , Mauvais Geneviève , Lherminier Jeanine , Michel Joël , Wang Xiao-Dong , Viel Christophe , Cachon Rémy 
Published: July 2007

The sensitivity of Sporidiobolus ruinenii yeast to the use of reducing agents, reflected in changes in the oxidoreduction potential at pH 7 (Eh7) environment, ricinoleic acid methyl ester catabolism, γ-decalactone synthesis, cofactor level, β-oxidation activity, and ultrastructure of the cell, was studied. Three environmental conditions (corresponding to oxidative, neutral, and reducing conditions) were fixed with the use of air or air and reducing agents (hydrogen and dithiothreitol). Lowering Eh7to neutral conditions (Eh7 = +30 mV and +2.5 mV) favoured the production of lactone more than the more oxidative condition (Eh7 = +350 mV). In contrast, when a reducing condition was used (Eh7= –130 mV), the production of γ-decalactone was very low. These results were linked to changes in the cofactor ratio during lactone production, to the β-oxidation activity involved in decanolide synthesis, and to ultrastructural modification of the cell.
Blind trials evaluating in vitro infectivity ofCryptosporidiumoocysts using cell culture immunofluorescence
Authors: Bukhari Zia , Holt David M. , Ware Michael W. , Schaefer Frank W. 
Published: July 2007

An optimized cell culture immunofluorescence (IFA) procedure, using the HCT-8 cell line, was evaluated in blind trials to determine the sensitivity and reproducibility of measuring the infectivity of flow-cytometry-prepared inocula of Cryptosporidium parvum oocysts. In separate trials, suspensions consisting of between 0% and 100% viable oocysts were prepared at the US Environmental Protection Agency, shipped to the American Water Laboratory, and analyzed blindly by cell culture IFA. Data indicated the control (100% live) oocyst suspensions yielded statistically similar results to cell culture dose–response curve data developed previously at the American Water Laboratory. For test samples containing oocyst suspensions of unknown infectivity, cell culture IFA analyses indicated a high degree of correlation (r2= 0.89; n = 26) with the values expected by the US Environmental Protection Agency. Cell culture infectivity correlates well with neonatal mouse infectivity assays, and these blind validation trials provide credibility for the cell culture IFA procedure as a cost-effective and expedient alternative to mouse infectivity assays for determining in vitro infectivity of C. parvum oocysts.
Purification and characterization ofEnterobacter sakazakiienterotoxin
Authors: Raghav Mamta , Aggarwal P.K. 
Published: July 2007

Enterobacter sakazakii has recently been recognized as an often fatal neonatal pathogen that rarely infects adults. Although not much is known about factors involved in its pathogenicity, the organism has been reported to produce enterotoxin. Currently, no information is available in the literature about the production and characterization of the enterotoxin. This report is the first attempt regarding purification and biochemical characterization of the enterotoxin produced from E. sakazakii. The toxin was purified by ammonium sulfate precipitation, followed by DEAE cellulose ion exchange and desalting by Sephadex™ G-100. The 66 kDa toxin was most active at pH 6 and was stable at 90 °C for 30 min. This stability combined with the potent activity of the toxin (LD50= 56 pg) emphasizes the potential risk to neonates fed infant milk formula contaminated with E. sakazakii. Further detailed molecular biological studies on the toxin are warranted in view of its stability and activity.
Detection of filamentous genus Gordonia in foam samples using genus-specific primers combined with PCR – denaturing gradient gel electrophoresis analysis
Authors: Shen Fo-Ting , Huang Hsuan-Ru , Arun A.B. , Lu Hui-Ling , Lin Ta-Chen , Rekha P.D. , Young Chiu-Chung 
Published: July 2007

A nested-PCR amplification combined with denaturing gradient gel electrophoresis (PCR–DGGE) approach was used to detect and identify Gordonia populations from wastewater treatment plant foam samples. The PCR-amplified region (position 722–1119) by specifically designed primers G699F and G1096R covered the hypervariable region of the Gordonia 16S rRNA gene sequence. This approach successfully distinguished Gordonia species to the interspecies level. The differential ability of PCR–DGGE analysis was effectively used to separate 12 Gordonia species belonging to different 16S rRNA gene-based phylogenetic lineages into 8 groups. Based on this method, the minimum limit of Gordonia detection was 5 × 104CFU·g–1in the seeded soil samples. The PCR–DGGE bands obtained were excised and identified by sequence analysis. Gordonia polyisoprenivorans , Gordonia amicalis , DGGE type II Gordonia species, and an uncertain Gordonia species dominated the activated sludge foam samples. Results of this study indicate that the detection and analyses of genus Gordonia within a complex microbial community could be accomplished using the PCR–DGGE approach to a larger extent, with certain limitations. Detection of diverse Gordonia populations in foam samples from wastewater treatment plants revealed the significant role of Gordonia in biological foaming during wastewater treatment. The nested-PCR amplification and DGGE can be used as a diagnostic tool for the early detection of foaming incidents in wastewater treatment plants using Gordonia as indicator organism.
Characterization ofBacillusandPseudomonasstrains with suppressive traits isolated from tomato hydroponic-slow filtration unit
Authors: Renault D. , Déniel F. , Benizri E. , Sohier D. , Barbier G. , Rey P. 
Published: July 2007

Bacillus and Pseudomonas spp. are known to be involved in plant pathogenic fungi elimination during the slow filtration process used in tomato soilless cultures. We isolated 6–8 strains of both Bacillus and Pseudomonas from the top, middle, and bottom sections of filters and identified them after 16S rDNA sequencing. Four Pseudomonas strains were identified as Pseudomonas fulva , 5 as Pseudomonas plecoglossicida , and 12 as Pseudomonas putida . The use of specific oligonucleotide polymerase chain reaction primer sets designed from gyrB gene sequences additionally permitted the identification of 17 Bacillus cereus and 3 Bacillus thuringiensis strains. Ribotyping with EcoRI pointed out an important polymorphism within Bacillus and Pseudomonas strains. Molecular characterization did not reveal a correlation between the location of isolates within the filter (top, middle, or bottom) and bacterial identification or riboclusters. Functional aspects assessed by community-level physiological profiling showed marked phenotypic differences between Pseudomonas communities isolated from the top and bottom filter layers; differences were lower between Bacillus communities of different layers and far less noticeable between mixed communities of Bacillus and Pseudomonas. These strains were tested for several suppressive activities. Conversely to most Bacillus, the majority of Pseudomonas strains were auxin producers and promoted the growth of tomato plantlet roots. On the other hand, only Bacillus strains displayed antagonistic activities by inhibiting the growth of pathogenic fungi frequently detected in soilless cultures. Siderophores were produced by nearly all bacteria, but at higher amounts by Pseudomonas than Bacillus strains. The biocontrol agent potentiality of certain strains to optimize the slow filtration process and to promote the suppressive potential of nutrient solution is discussed.
Predicting green and dry mass of yellow-poplar: an integral approachWest Virginia Agriculture and Forestry Experiment Station Scientific Article 2962.
Authors: Brooks John R. , Jiang Lichun , Zhang  Yujia 
Published: July 2007

An integral approach to estimating stem green and dry masses for yellow-poplar (Liriodendron tulipifera L.) in West Virginia was compared with traditional ratio equation methods. The data were based on stem analysis of 26 trees from the Central Appalachian Broadleaf Forest province in northern West Virginia and 18 trees from the Eastern Broadleaf Forest province in west-central West Virginia. Sample disks were extracted from 0.3 m, 0.6 m, 1.37 m, 1.8 m, and then every 1.2 m to an approximate 7.6 cm top diameter outside bark. Sample trees ranged from 17.3 cm to 56.1 cm in diameter and from 18.8 m to 38.5 m in total height. The proposed equation generally performed better for the whole tree as well as for sections within the tree based on the nine relative height classes examined. A constant wood-density equation was superior to the use of a linear wood-density equation as a function of height above the ground. The proposed equation explained over 90% of the variation in stem mass and compared favorably with existing fixed merchantable top mass equations.
Modeling corewood–outerwood transition in loblolly pine using wood specific gravity
Authors: Mora Christian R. , Allen H. Lee , Daniels Richard F. , Clark Alexander 
Published: July 2007

A modified logistic function was used for modeling specific-gravity profiles obtained from X-ray densitometry analysis in 675 loblolly pine ( Pinus taeda L.) trees in four regeneration trials. Trees were 21 or 22 years old at the time of the study. The function was used for demarcating corewood, transitional, and outerwood zones. Site and silvicultural effects were incorporated into the model. Heteroscedasticity and within-group correlation were accounted for by specifying the variance and serial-correlation structure, respectively. The estimated transition zone was located between rings 5 and 15, and the outerwood demarcation point varied from rings 12 to 15. No effects of treatments on the demarcation points were observed; however, site preparation and fertilization affected the lower asymptotes of the curves in all sites. A geographical trend for the demarcation point was observed, with the northern site requiring more time to reach a plateau in specific gravity compared with the southern sites. The diameter of the juvenile core was increased as a result of the treatments. However, the amount of corewood was not statistically affected, ranging from 55% in the north to 75% in the south, except at one site where fertilization decreased the percentage of corewood.
Bridging native and scientific observations of snowshoe hare habitat restoration after clearcutting to set wildlife habitat management guidelines on Waswanipi Cree land
Authors: Jacqmain Hugo , Bélanger Louis , Hilton Susanne , Bouthillier Luc 
Published: July 2007

Large-scale timber harvesting in the northern black spruce forest, on Quebec Cree territory, causes immediate loss of productive wildlife habitat for Cree hunters. Duration of this impact is key information to improve forest management. The objective here was to examine the postharvesting habitat restoration delay for snowshoe hare, a species valuable to Cree hunters, as well as a wildlife indicator of the sapling stage. A minimum threshold for vegetation development was established, at which the return of hare populations is considered acceptable by Cree hunters. To do so, an adaptive approach was used, combining Cree hunter knowledge and biological assessment. Hare populations were monitored in 36 cut blocks, ranging from 0 to 30 years after harvest. Cree hunters were interviewed to determine when a cut block becomes adequate for snaring. The combined analysis of the two knowledge sources indicated that stands that meet the threshold average 4 m in height, 6300 trees/ha in density, and are aged between 13 and 27 years. Current regulation sets this threshold at 3 m in height, regardless of cut block scale, and at 20 years postcut when considering family hunting ground scale, and thus, does not fully meet sustainable resource development objectives.
Modelling the influence of weed competition on growth of young Pinus radiata. Development and parameterization of a hybrid model across an environmental gradient
Authors: Watt Michael S. , Kimberley Mark O. , Coker Graham , Richardson Brian , Estcourt George 
Published: July 2007

A hybrid tree growth model sensitive to competition from a diverse range of weed species was developed and validated using data from a nationwide series of 24 plots covering an extensive environmental gradient. Tree growth in plots with weeds over the first 3 years following establishment was predicted by reducing potential growth from an empirically determined optimum rate for the site (weed free) using a competition modifier, which accounts for the degree of weed competition for both light and water availability. Diameter growth of trees in plots with weeds was initially predicted by including a light competition modifier into the model developed for weed-free plots. This model accounted for 87% of the variance in diameter of trees growing with weeds. Although inclusion of this modifier provided unbiased predictions of tree diameter growth on wet sites, model predictions overestimated diameter growth on dryland sites by on average 11%. Addition of a competition index for water based on treatment differences in average fractional available root-zone volumetric water content significantly (p < 0.001) improved the precision (R2 = 0.96) and reduced the bias of the overall model. A cross validation of this final model indicated it was unbiased and relatively accurate (R2 = 0.95).
Winter conditions in eastern hemlock and mixed-hardwood deer wintering areas of Vermont
Authors: Lishawa Shane C. , Bergdahl Dale R. , Costa Scott D. 
Published: July 2007

In regions experiencing harsh winter, eastern hemlock ( Tsuga canadensis (L.) Carrière) is thought to moderate winter conditions and provide cover for white-tailed deer ( Odocoileus virginianus Zimmerman, 1780). In Vermont, USA, eastern hemlock is the dominant tree in many white-tailed deer wintering areas. Hemlock woolly adelgid ( Adelges tsugae Annand; HWA), an insect introduced from Asia, is causing widespread mortality of eastern hemlock. HWA cold-hardiness research and cold-hardiness zone climate models predict that HWA is capable of winter survival in portions of southern Vermont. This study quantifies the effects of eastern hemlock cover on winter temperatures and snow depths and assesses the effect of hemlock dominance on the winter severity values for white-tailed deer and on cold hardiness zone designations. Within site-paired eastern hemlock and hardwood stands, temperatures were recorded at 30 min intervals and snow depths were recorded every 2 weeks in the winters of 2003–2004 and 2004–2005. Extreme temperatures and snow depths were significantly moderated within hemlock stands. In southern Vermont, eastern hemlock mortality caused by HWA will alter these pockets of moderated microclimate, adding additional stress to white-tailed deer. Furthermore, the magnitude of temperature buffering in hemlock stands suggests that HWA may be capable of winter survival farther north than previously estimated.
Dwarf mistletoe effects on fuel loadings in ponderosa pine forests in northern Arizona
Authors: Hoffman Chad , Mathiasen Robert , Sieg Carolyn Hull 
Published: July 2007

Southwestern dwarf mistletoe ( Arceuthobium vaginatum (Willd.) J. Presl ssp. cryptopodum ) infests about 0.9 million ha in the southwestern United States. Several studies suggest that dwarf mistletoes affect forest fuels and fire behavior; however, few studies have quantified these effects. We compared surface fuel loadings and predicted fire behavior among four levels of dwarf mistletoe infestation (none, light, moderate, and severe) in a total of 239 plots on 11 sites on basaltic soils in northern Arizona. In each plot we measured tree attributes, dwarf mistletoe rating and surface fuel loading. Stands severely infested by dwarf mistletoe had lower (P < 0.05) tree density and higher snag density, but higher (P < 0.05) total surface fuel loadings and total fuel loadings >7.62 cm and <7.62 cm, than non-infested stands. However, there were no statistical differences in any canopy fuel variables among infestation classes. Predicted fire behavior indicated that the wind speed required to promote the spread of a surface fire into the canopy was lower in severely infested stands than in non-infested stands. These results suggest that stands in northern Arizona that are severely infested with dwarf mistletoe should be priority areas for fuels treatments.
Combining microsatellites, growth, and adaptive traits for managing in situ genetic resources ofEucalyptus urophylla
Authors: Tripiana Vincent , Bourgeois Michaël , Verhaegen Daniel , Vigneron Philippe , Bouvet Jean-Marc 
Published: July 2007

Genetic diversity and structure of 17 populations representative of the natural range of Eucalyptus urophylla S.T. Blake in Indonesia were analysed with 10 microsatellite markers. Two provenance and progeny trials, using the same populations, were established in the Republic of the Congo and analysed for growth and survival at 37 months. Observed microsatellite heterozygosity (Ho) was moderate to high within populations (Ho= 0.51–0.72). The index of fixation (FIS) was significantly different from zero for all populations (FIS= 0.13–0.31) and possibly resulted from a Wahlund effect. The differentiation parameter was low (FST= 0.04) and not significantly different from zero, which can be explained by effective gene flow via pollen. The genetic variances within and among provenances for survival and growth traits were significantly different from zero, representing 13%–23% and 14%–50% of the total variation, respectively. The differentiation between populations based on quantitative traits was marked (QST= 0.07–0.33). A negative relationship between altitude of the seed source and its performance in the Congo was observed (R2= 0.59–0.67) and could be explained by the effect of natural selection along the altitudinal gradient. This marked differentiation for quantitative traits despite high apparent gene flow results in a clinal variation, which suggests the use of altitude of seed source as an important principle for in situ or ex situ management of E. urophylla genetic resources.
The relationship between tree growth patterns and likelihood of mortality: a study of two tree species in the Sierra Nevada
Authors: Das Adrian J. , Battles John J. , Stephenson Nathan L. , van Mantgem Phillip J. 
Published: July 2007

We examined mortality of Abies concolor (Gord. & Glend.) Lindl. (white fir) and Pinus lambertiana Dougl. (sugar pine) by developing logistic models using three growth indices obtained from tree rings: average growth, growth trend, and count of abrupt growth declines. For P. lambertiana, models with average growth, growth trend, and count of abrupt declines improved overall prediction (78.6% dead trees correctly classified, 83.7% live trees correctly classified) compared with a model with average recent growth alone (69.6% dead trees correctly classified, 67.3% live trees correctly classified). For A. concolor, counts of abrupt declines and longer time intervals improved overall classification (trees with DBH ≥20 cm: 78.9% dead trees correctly classified and 76.7% live trees correctly classified vs. 64.9% dead trees correctly classified and 77.9% live trees correctly classified; trees with DBH <20 cm: 71.6% dead trees correctly classified and 71.0% live trees correctly classified vs. 67.2% dead trees correctly classified and 66.7% live trees correctly classified). In general, count of abrupt declines improved live-tree classification. External validation of A. concolor models showed that they functioned well at stands not used in model development, and the development of size-specific models demonstrated important differences in mortality risk between understory and canopy trees. Population-level mortality-risk models were developed for A. concolor and generated realistic mortality rates at two sites. Our results support the contention that a more comprehensive use of the growth record yields a more robust assessment of mortality risk.