Effect of drying and rewetting on bacterial growth rates in soil

The effect of soil moisture on bacterial growth was investigated, and the effects of rewetting were compared with glucose addition because both treatments increase substrate availability. Bacterial growth was estimated as thymidine and leucine incorporation, and was compared with respiration. Low growth rates were found in air-dried soil, increasing rapidly to high stable values in moist soils. Respiration and bacterial growth at different soil moisture contents were correlated. Rewetting air-dried soil resulted in a linear increase in bacterial growth with time, reaching the levels in moist soil (10 times higher) after about 7 h. Respiration rates increased within 1 h to a level >10 times higher than that in moist soil. After the initial flush, there was a gradual decrease in respiration rate, while bacterial growth increased to levels twice that of moist soil 24 h after rewetting, and decreased to levels similar to those in moist soil after 2 days. Adding glucose resulted in no positive effect on bacterial growth during the first 9 h, despite resulting in more than five times higher respiration. This indicated that the initial increase in bacterial growth after rewetting was not due to increased substrate availability.     

Impact of impregnation time and chip size on sugar yield in pretreatment of softwood for ethanol production

Efficient pretreatment is necessary to make the wood-to-ethanol process more feasible. In this study, chips of different sizes were impregnated with SO₂ and steam-pretreated. Dilute-acid pretreatment together with subsequent enzymatic hydrolysis resulted in solubilization of between 69% and 73% of the fermentable sugars (glucose and mannose) in the raw material for the combinations of impregnation times and chip sizes investigated. Shorter impregnation times resulted in slightly lower mannose yields for the larger chips, probably due to poor diffusion of the catalyst. Small differences in glucose yield after enzymatic hydrolysis showed that the overall glucose yield was slightly higher for the smaller chips, however, whether the increased energy demand and cost of size reduction is compensated for by the higher yield, requires techno-economical evaluations.     

Effect of DNA complexation and freeze-drying on the physicochemical characteristics of cationic liposomes

We describe the use of saccharides, such as sorbitol, mannitol, sucrose, maltodextrin, and dextran, as cyoprotectants for freeze-drying cationic liposomes. Saccharides can protect liposomes either by interacting with phospholipid headgroups or by forming an amorphous glass surrounding the vesicles, thus preventing aggregation, mechanical rupture of membrane, fusion of liposomes, and drug leakage. We have particularly considered liposome characteristics, such as size, zeta potential, and ability in complexing DNA, before and after freeze-drying. Our study indicates that cationic liposomes are able to maintain liposome characteristics after lyophilization and rehydration and maintain the ability to complex DNA even if the strength of the interaction forces was of lower intensity with respect to liposomes before lyophilization.     

Insulin-loaded alginate microspheres for oral delivery – Effect of polysaccharide reinforcement on physicochemical properties and release profile

Oral administration of insulin requires protein protection from degradation in the gastric environment and its absorption improvement in the intestinal tract. To achieve this objective several types of microspheres composed of alginate, chitosan and dextran sulphate have been prepared by ionotropic gelation. Parameters such as the mean particle size, swelling behaviour, insulin encapsulation efficiency, loading capacity and release profiles in simulated gastric and intestinal fluids have been compared for the systems developed. In this study, attempts have been made to increase insulin protection and to improve its release from microspheres by reinforcing the alginate matrix with chitosan and/or dextran sulphate. Dextran sulphate was able to avoid insulin release at pH 1.2, protecting the protein from the acidic environment and reducing the total insulin released at pH 6.8. This effect was explained by an interaction between the permanent negatively charged groups of dextran sulphate and insulin molecules.     

Sol-gel treatments on cotton fabrics for improving thermal and flame stability: Effect of the structure of the alkoxysilane precursor

Sol-gel treatments have been performed on cotton fabrics in order to promote the formation of a surface silica insulating barrier, able to enhance their thermo-oxidative stability and flame retardancy. In particular, the role of several silica precursors, which differ as far as their structure (number and type of hydrolysable groups, presence of aromatic rings) is concerned, has been thoroughly investigated. The level of silica distribution and dispersion on and within the fabrics was found to depend on the type of precursor employed, as revealed by scanning electron microscopy and elemental analysis. All the precursors were able to favour the char formation in air below 360 °C, as stated by thermogravimetric analysis: in particular, the highest thermal stability was achieved in the presence of precursors bearing aromatic rings. Indeed, both flammability resistance and combustion behaviour of the treated fabrics were remarkably enhanced.     

Effect of heat–moisture treatment on the structure and physicochemical properties of tuber and root starches

Starch from tubers potato (Solanum tuberosum), taro (Alocassia indica), new cocoyam (Xanthosoma sagitifolium), true yam (Dioscorea alata), and root cassava, (Manihot esculenta) crops was isolated and its morphology, composition and physicochemical properties were investigated before and after heat–moisture treatment (HMT) (100 °C, for 10 h at a moisture content of 30%). Native starch granules were round to oval to polygonal with smooth surfaces. The granule size (diameter) ranged from 3.0 to 110 μm.The total amylose content ranged from 22.4 to 29.3%, of which 10.1–15.5% was complexed by native lipid. The phosphorus content ranged from 0.01 to 0.1%. The X-ray pattern of potato and true yam was of the ‘B’-type. Whereas, that of new cocoyam and taro was of the ‘A’-type. Cassava exhibited a mixed ‘A+B’-type X-ray pattern. The relative crystallinity, swelling factor (SF), amylose leaching (AML), gelatinization temperature range and the enthalpy of gelatinization of the native starches ranged from 30 to 46, 22 to 54, 5 to 23%, 13 to 19 °C and 12 to 18 J/g, respectively. Susceptibility of native starches towards hydrolysis by 2.2N HCl and porcine pancreatic -amylase were 60–86% (after 12 days), and 4–62% (after 72 h), respectively. Retrogradation was most pronounced in the B-type starches. Granule morphology remained unchanged after HMT. The X-ray pattern of the B-type starches was altered (B→A+B) on HMT. However, that of the other starches remained unchanged. HMT decreased SF, AML, gelatinization enthalpy and susceptibility towards acid hydrolysis, but increased gelatinization temperatures and enzyme susceptibility. Extent of retrogradation and relative crystallinity decreased on HMT of true yam and potato starches, but remained unchanged in the other starches. The foregoing data showed that changes in physicochemical properties on HMT are influenced by the interplay of crystallite disruption, starch chain associations and disruption of double helices in the amorphous regions.     

Effect of acid–alcohol treatment on the molecular structure and physicochemical properties of maize and potato starches

The molecular structure and physicochemical properties of acid–alcohol treated maize and potato starches (0.36% HCl in methanol at 25 °C for 1–15 days) were investigated. The yields of the modified starches were ranging from 91 to 100%. The average granule size of modified starches decreased slightly. The solubility of starches increased with the increase of treatment time, and the pasting properties confirmed the high solubility of modified starches. The gelatinization temperatures and range of gelatinization increased with the increase of treatment time except T_o (onset temperature) of maize starch. Molecular structures of modified starches suggested the degradation of starches occurred mostly within the first 5 days of treatment, and degradation rate of potato starch was higher than maize starch both in amylopectin and in amylose. Maize starch was found less susceptible to acid–alcohol degradation than potato starch.     

Effect of vacuum drying on protein-mannitol interactions: The physical state of mannitol and protein structure in the dried state

The purpose of the present studies was to systematically investigate protein-mannitol interactions using vacuum drying, to obtain a better understanding of the effect of protein/mannitol wt/wt ratios on the physical state of mannitol and protein secondary structure in the dried state. Solutions containing β-lactoglobulin (βLg):mannitol (1∶1–1∶15 wt/wt) were vacuum dried at 5°C under 3000 mTorr of pressure. The physical state of mannitol was studied using x-ray powder physical state of mannitol was studied using x-ray powder diffractometry (XRPD), polarized light microscopy (PLM), Fourier-transform infrared (FTIR) spectroscopy, and modulated differential scanning calorimetry (MDSC). XRPD studies indicated that mannitol remained amorphous up to 1∶5 wt/wt βLg:mannitol ratio, whereas PLM showed the presence of crystals of mannitol in all dried samples except for the 1∶1 wt/wt βLg:mannitol dried sample. FITR studies indicated that a small proportion of crystalline mannitol was present along with the amorphous mannitol in dried samples at lower (less than 1∶5 wt/wt) βLg:mannitol ratios. The T_g of the dried 1∶1 wt/wt βLg:mannitol sample was observed at 33.4°C in MDSC studies, which indicated that at least a part of mannitol co-existed with protein in a single amorphous phase. Evaluation of the crystallization exotherms indicated that irrespective of the βLg:protein wt/wt ratio in the initial sample, the protein to amorphous mannitol ratio was below 1∶1 wt/wt in all dried samples. Second-derivative FTTR studies on dried βLg and recombinant human interferon α-2a samples showed that mannitol affected protein secondary structure to a varying degree depending on the overall mannitol content in the dried sample and the type of protein.     

Effect of the cross-linked reagent type on some morphological,physicochemical and functional characteristics of banana starch (Musa paradisiaca)

Cross-linked starches have increased their importance due to their applications such as adsorbents of heavy metals. In this work the effect the reagent used in the chemical modification of banana starch and its impact on some morphological, physicochemical and functional characteristics was evaluated. The reagent used in the cross-linked of starch decreased the fat and protein content, whereas ash level were higher. The morphology of the granules, observed by scanning electron microscopy, was more affected when a blend of sodium trimetaphosphate (STMP)/sodium tripolyphosphate (STPP) and epichlorohydrin (EPI) were used in the modification. The cross-linked starches presented a bimodal distribution and the effect was more conspicuous in those starches modified with STMP/STPP and EPI. The swelling value (60 °C) increased with the cross-linking and the highest value was obtained in those starches modified with STMP/STPP and EPI. However, at higher temperatures the swelling values of cross-linked starches with STMP/STPP and EPI decreased as temperature increased (80 °C), and there after the value was constant. The cross-linked starches with STMP/STPP and EPI showed the lowest solubility values. The cross-linked starch with POCl₃ (phosphorous oxychloride) showed a slight decrease in the onset and peak temperatures compared with its native counterpart, but those modified with STMP/STPP and EPI presented an increase in the three transition temperatures, but a decrease in enthalpy value. The results obtained can be used to determine the type of reagent used for cross-linked in order to obtain a starch with specific characteristics.     

Effect of process parameters on the production and drying of Leuconostoc mesenteroides cultures

Leuconostoc mesenteroides BLAC was grown on MRS broth or on a carrot juice medium, and the effects of sugar concentration, type of pH control, aeration and fermentor size on viable counts were examined. The effect on viability of the type of centrifuge used to concentrate the bacterial culture was also examined. When the MRS broth had the traditional 110 mM glucose, pH control did not increase the final population. However, using a zone pH control mode, increasing the glucose content of MRS both from 110 to 220 mM almost doubled the population. In MRS broth, the amount of acetic acid produced was the same for all treatments, and was proportional to the amount of citrate consumed. There was a significantly lower cell yield in the carrot juice medium when the pH was not regulated. In the carrot juice medium, pH had a more pronounced effect on the final population level than did aeration, even though the quantity of viable cells was greater when the culture was aerated. In MRS broth, glucose was completely consumed during fermentation, but this was not the case in carrot juice medium. Aeration resulted in increased acetic acid content of the fermented medium. Viable counts were not affected by scaling the volume of the fermentation from 2 to 15 l ,or by the type of centrifuge used to concentrate the cells. Cells were concentrated by a factor of 10, but in both centrifuge types, viable counts showed only an eightfold average increase. However, freeze-dried powders obtained from the continuous pilot-plant-centrifuged cultures had, on the average, 33% lower populations than those obtained from the laboratory unit. Journal of Industrial Microbiology & Biotechnology (2002) 28, 291–296 DOI: 10.1038/sj/jim/7000245 Received 09 July 2001/ Accepted in revised form 25 January 2002     

Theoretical study on the thermal decomposition of model compounds for Poly (dialkyl fumarate)

The thermal decomposition of model compounds for poly (dialkyl fumarate) was studied by using ab initio and density functional theory (DFT) calculations. To determine the most favorable reaction pathway of thermal decomposition, geometries, structures, and energies were evaluated for reactants, products, and transition states of the proposed pathways at the HF/6-31G(d) and B3LYP/6-31G(d) levels. Three possible paths (I, II and III) and subsequent reaction paths (IV and V) for the model compounds of poly (dialkyl fumarate) decomposition had been postulated. It has been found that the path (I) has the lowest activation energy 193.8 kJ mol⁻¹ at B3LYP/6-31G(d) level and the path (I) is considered as the main path for the thermal decomposition of model compounds for poly (dialkyl fumarate).      

Effect of DNA length and H4 acetylation on the thermal stability of reconstituted nucleosome particles

To examine the factors involved with nucleosome stability, we reconstituted nonacetylated particles containing various lengths (192, 162, and 152 base pairs) of DNA onto the Lytechinus variegatus nucleosome positioning sequence in the absence of linker histone. We characterized the particles and examined their thermal stability. DNA of less than chromatosome length (168 base pairs) produces particles with altered denaturation profiles, possibly caused by histone rearrangement in those core-like particles. We also examined the effects of tetra-acetylation of histone H4 on the thermal stability of reconstituted nucleosome particles. Tetra-acetylation of H4 reduces the nucleosome thermal stability by 0.8 degrees C as compared with nonacetylated particles. This difference is close to values published comparing bulk nonacetylated nucleosomes and core particles to ones enriched for core histone acetylation, suggesting that H4 acetylation has a dominant effect on nucleosome particle energetics.     

Effect of the agitation on the adsorption and hydrolytic efficiency of cutinases on polyethylene terephthalate fibres

The effect of agitation on adsorption, desorption and hydrolytic efficiency of a native and a genetically modified cutinase (L182A) on polyethylene terephthalate fibres is reported in this paper. The effect of mechanical agitation was studied using a shaker bath with orbital agitation and a Rotawash machine with vertical agitation with and without extra steel discs inside the reaction pots. The results obtained indicate that mechanical agitation combined with enzymatic action enhances the adsorption and activity of cutinases towards PET (polyethylene terephthalate) fibres. L182A showed higher adsorption than the native enzyme for all the levels of mechanical agitation. Lower units of L182A lead to similar yields of terephthalic acid formed in all levels of mechanical agitation. The highest increase of hydroxyl surface groups was found for the genetically modified L182A at the lowest level of mechanical agitation with a shaker bath. These results indicate that enzymatic functionalization of PET is favoured with a process with lower levels of mechanical agitation.     

Effect of ice fraction and dilution factor on the antifreeze activity in the hemolymph of the cerambycid beetle Rhagium inquisitor

The freezing-melting hysteresis in a given volume of hemolymph from the cerambycid beetle Rhagium inquisitor was linearly and negatively related to the logarithm of the mass fraction of ice in the sample. When the ice fraction dropped by a factor of 10, the hysteresis activity increased by about 2 degrees C. When the hemolymph was diluted, the hysteresis activity was linearly and negatively related to the logarithm of the dilution factor. Dilution of the hemolymph by a factor of 2 led to a 1 degree C reduction in hysteresis activity. In the diluted samples, the ice growth took place along the a-axes, implying that the antifreeze peptides of insects block ice growth along the c-axis, in addition to the a-axis.     

Effect of phosphorylation on the thermal and light stability of the thylakoid membranes

Higher plant thylakoid membranes contain a protein kinase that phosphorylates certain threonine residues of light-harvesting complex II (LHCII), the main light-harvesting antenna complexes of photosystem II (PSII) and some other phosphoproteins (Allen, Biochim Biophys Acta 1098:275, 1992). While it has been established that phosphorylation induces a conformational change of LHCII and also brings about changes in the lateral organization of the thylakoid membrane, it is not clear how phosphorylation affects the dynamic architecture of the thylakoid membranes. In order to contribute to the elucidation of this complex question, we have investigated the effect of duroquinol-induced phosphorylation on the membrane ultrastructure and the thermal and light stability of the chiral macrodomains and of the trimeric organization of LHCII. As shown by small angle neutron scattering on thylakoid membranes, duroquinol treatment induced a moderate (~10%) increase in the repeat distance of stroma membranes, and phosphorylation caused an additional loss of the scattering intensity, which is probably associated with the partial unstacking of the granum membranes. Circular dichroism (CD) measurements also revealed only minor changes in the chiral macro-organization of the complexes and in the oligomerization state of LHCII. However, temperature dependences of characteristic CD bands showed that phosphorylation significantly decreased the thermal stability of the chiral macrodomains in phosphorylated compared to the non-phosphorylated samples (in leaves and isolated thylakoid membranes, from 48.3°C to 42.6°C and from 47.5°C to 44.3°C, respectively). As shown by non-denaturing PAGE of thylakoid membranes and CD spectroscopy on EDTA washed membranes, phosphorylation decreased by about 5°C, the trimer-to-monomer transition temperature of LHCII. It also enhanced the light-induced disassembly of the chiral macrodomains and the monomerization of the LHCII trimers at 25°C. These data strongly suggest that phosphorylation of the membranes considerably facilitates the heat- and light-inducible reorganizations in the thylakoid membranes and thus enhances the structural flexibility of the membrane architecture.     

Effect of culture medium and cryoprotectants on the growth and survival of probiotic lactobacilli during freeze drying

Aims:  To investigate the effects of the medium and cryoprotective agents used on the growth and survival of Lactobacillus plantarum and Lactobacillus rhamnosus GG during freeze drying.
Methods and Results:  A complex medium was developed consisting primarily of glucose, yeast extract and vegetable-derived peptone. Trehalose, sucrose and sorbitol were examined for their ability to protect the cells during freeze drying. Using standardized amount of cells and the optimized freeze drying media, the effect of the growth medium on cell survival during freeze drying was investigated. The results showed that glucose and yeast extract were the most important growth factors, while sucrose offered better protection than trehalose and sorbitol during freeze drying. When the cells were grown under carbon limiting conditions, their survival during freeze drying was significantly decreased.
Conclusions:  A clear relationship was observed between cell growth and the ability of the cells to survive during the freeze drying process.
Significance and Impact of the Study:  The survival of probiotic strains during freeze drying was shown to be dependent on the cryoprotectant used and the growth medium.     

Effects of resource supplies on the structure and function of microbial communities

The supplies of nutrients, and their elemental stoichiometry, can have significant impacts upon the structure and function of microbial communities. This review focuses on the effects of nutrient supplies on the biodegradation of organic matter, and on the dynamics of host-pathogen interactions. Analyses of data from the literature suggest significant effects of nitrogen:phosphorus supply ratios on the microbial decomposition of organic matter, and it is argued that these stoichiometric effects may have important implications for the fate and fluxes of carbon in natural ecosystems. In addition, it is shown that the supplies of nitrogen and phosphorus to the host can strongly influence the outcome of infections in both terrestrial and aquatic plants, suggesting that resource availability and resource supply ratios potentially may have significant effects on the health of many plant communities. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of thermal stress and water deprivation on the acetylcholinesterase activity of the pig brain and hypophyses

The effects of direct exposure of boars to thermal stress for 1 h daily for 5 days and to acute water deprivation for 24 or 48 h were studied on the acetylcholinesterase (AChE) activity of porcine brain and hypophysial regions. Mean ambient temperatures, respiratory rates and rectal temperatures in the open were significantly higher than inside the pen. Heat stress induced a rise in AChE activities in the pons, cerebellum, amygdala, hippocampus, hypothalamus, mid-brain and medulla oblongata. However, no significant changes were observed in the cerebral cortex, adenohypophysis and neurohypophysis. Water deprivation significantly (P<0.05) depressed AChE activity to varying extents depending on the duration of water restriction. Thus AChE activity in the amygdala was depressed by water deprivation for 24 h but partially restored at 48 h. The pons and medulla oblongata were comparable to the amygdala in this respect. The adenohypophysis and neurohypophysis were relatively unaffected.     

Influence of spring and summer water temperature on brook charr, Salvelinus fontinalis, growth and age structure in the Ford River, Michigan

Synopsis The influence of late spring and summer water temperatures on brook charr, Salvelinus fontinalis, growth and age structure was evaluated from 1984 to 1991 in the Ford River, Michigan. Temperature was monitored and brook charr sampled for vital statistics from late May through September using fyke nets and weirs at four locations within a 25.8 km section of stream. Scale analysis was used to determine captured brook charr age, past length at age and relative annual growth rates. Late spring and summer water temperature patterns varied between years with the greatest variability occurring in May and June. Age and size structure also varied between years and was significantly related to temperature. Years with cooler late spring and summer temperature patterns were dominated by older (age 2 and 3), larger brook charr, while years with warmer spring and summer temperature patterns were dominated by younger (age 1), smaller brook charr. Spring and summer temperature did not appear to have a significant effect on the growth of age 0 or age 1 brook charr. However, temperature was negatively related to brook charr growth from age 2 on. As spring and summer water temperatures are critical to brook charr growth and survival, it is important that a streams thermal regime be considered when establishing management goals for this species.