Physicochemical and Rheological Characterization of Gum Tragacanth Exudates from Six Species of Iranian <Emphasis Type="Italic">Astragalus</Emphasis>

The flow behavior of six species of Iranian gum tragacanth dispersions was investigated at different temperatures and ionic strengths, within a concentration range (0.05–1.5% w/w) using a controlled shear rate rheometer. The steady shear measurements showed that all of the gum dispersions had shear-thinning natures. The power law model was used to describe the rheological properties of dispersions and Arrhenius model was used to evaluate the temperature effect. Composition analysis, surface tension measurement, particle size analysis, and color measurement of all the species were also carried out. The results indicated that the six species of gum tragacanth being studied in this paper exhibited significantly different physicochemical properties. Therefore, various species of gum tragacanth can be used instead of different hydrocolloids in a wide range of applications.     

Characterization,Release Profile and Antimicrobial Properties of Bioactive Polyvinyl Alcohol-Alyssum homolocarpum Seed Gum- Nisin Composite Film

A common goal of active packaging is to improve the shelf life, safety, or quality of packaged foods. The integrity of an active package must be remained in order to prevent the growth of microorganisms on the surface of food. Therefore, active polyvinyl alcohol-Alyssum homolocarpum seed gum (PVA-AHSG) composite films with different nisin concentrations (3000, 5000 and 10,000 IU) were prepared and their physico-chemical and antimicrobial properties were determined. Addition of nisin to the composite films increased their water vapor permeability (WVP), elongation at break (EB) and opacity, whereas their total color difference (ΔE), glass transition temperature (Tg), melting temperature (Tm), tensile strength (TS) and young modulus (YM) were decreased. Increasing the nisin concentration remarkably increased the chain mobility, interactions between polymers and water molecules and also the free volume of polymer matrix. The antimicrobial potential of film against L. monocytogene, S. aureus and E. coli as well as the release of nisin into phosphate buffer solution (pH 7.2) were investigated. Films containing nisin had inhibition effect against gram positive pathogens among which L. monocytogenes was the most sensitive bacterium. In liquid media, all films containing nisin prevented the growth of L. monocytogenes and S. aureus, but it was only the film with 10,000 IU nisin content which was able to control 100% of the microbial population during incubation time. Nisin release and diffusion coefficient (D) increased as its concentration increased in the film matrix due to the interaction of nisin with film polymer chains. Therefore, the resultant film had appropriate controlled release property and suitable microbial inhibitory against gram positive bacteria.

Composite bioactive films based on polyvinyl alcohol-Alyssum homolocarpum seed gum blend and Nisin: Physiochemical characterization and antimicrobial properties. Monjazeb et al. (2017).

     

A New Model to Describe Flow Behaviour of Concentrated Orange Juice

The knowledge of rheological behaviour of juices and fruit derivatives is very useful both in the prediction of their stability and in process design, and it depends on the type of juice and on the raw material with which they are produced. Most of the equations that have been used to quantify flow behaviour describe the evolution of shear stress with the change of shear rate. Nevertheless, the essential variable in equipment design is viscosity. In this way, a mathematical model to easily describe the evolution of apparent viscosity of these non-Newtonian fluids with the shear rate would be very useful. In this work, a mathematical expression has been developed, fitted to experimental data and compared with the Herschel–Bulkley one. The obtained parameters with concentrated orange juice followed these trends: equilibrium apparent viscosity (η _∞) scarcely changed with temperature. Static apparent viscosity (η ₀) decreased with increasing temperature, contrary to what happened with the flow behaviour constant k.     

Stability and folding dynamics of polyglutamic acid

The thermal stability and folding dynamics of polyglutamic acid were studied by equilibrium circular dichroism (CD), Fourier-transform infrared (FTIR), and time-resolved temperature-jump infrared (IR) spectroscopy. Polyglutamic acid (PGA) forms α-helical peptides in aqueous solution and is an ideal model system to study the helix–coil transition. Melting curves were monitored with CD and FTIR as a function of pD. At low pD, PGA aggregates at temperatures above 323 K, whereas at pD >5, unfolding and refolding are reversible. At pD 5.4, a helix–coil transition occurs with a transition temperature T _m of 307 K. At slightly higher pD of 6.2, the peptide conformation is already in a coil structure and only small conformational changes occur upon heating. We determined the equilibrium constant for the reversible helix–coil transition at pD 5.4. The dynamics of this transition was measured at single IR wavelengths after a nanosecond laser-excited temperature jump of ∆T ~ 10 K. Relaxation constants decreased with increasing peptide temperature. Folding and unfolding rates as well as activation energies were extracted based on a two-state model. Our study shows how equilibrium and time-resolved infrared spectroscopic data can be combined to characterize a structural transition and to analyze folding mechanisms.     

Germination responses of Diplotaxis harra to temperature and salinity

Diplotaxis harra (Forssk.) Boiss, an annual herb in the family of Brassicaceae, is widely distributed in many sandy and gypseous areas in southern Tunisia. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after seed transfer to distilled water. The germination responses of the seeds in complete darkness were determined over a wide range of temperatures (5, 10, 15, 20, 25 and 30 °C) and salinities (0, 50, 100, 150 and 200 mM NaCl). Germination was inhibited by either an increase or decrease in temperature from the optimal temperature (15 °C). Highest germination percentages were obtained under non-saline conditions and an increase in NaCl concentrations progressively inhibited seed germination. Rate of germination decreased with an increase in salinity at all temperatures but comparatively higher rates were obtained at 15 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 200 mM NaCl. Seeds were transferred from salt solution to distilled water after 20 days, and those from low salinities recovered at all temperatures. At NaCl concentration of 200 mM, the recovery of germination was completely inhibited.     

Thermal clamping of temperature-regulating flowers reveals the precision and limits of the biochemical regulatory mechanism

The flowers of several families of seed plants warm themselves when they bloom. In some species, thermogenesis is regulated, increasing the rate of respiration at lower ambient temperature (T _a) to maintain a somewhat stable floral temperature (T _f). The precision of this regulation is usually measured by plotting T _f over T _a. However, such measurements are influenced by environmental conditions, including wind speed, humidity, radiation, etc. This study eliminates environmental effects by experimentally ‘clamping’ T _f at constant, selected levels and then measuring stabilized respiration rate. Regulating flowers show decreasing respiration with rising T _f (Q ₁₀ < 1). Q ₁₀ therefore becomes a measure of the biochemical ‘precision’ of temperature regulation: lower Q ₁₀ values indicate greater sensitivity of respiration to T _f and a narrower range of regulated temperatures. At the lower end of the regulated range, respiration is maximal, and further decreases in floral temperature cause heat production to diminish. Below a certain tissue temperature (‘switching temperature’), heat loss always exceeds heat production, so thermoregulation becomes impossible. This study compared three species of thermoregulatory flowers with distinct values of precision and switching temperature. Precision was highest in Nelumbo nucifera (Q ₁₀ = 0.16) moderate in Symplocarpus renifolius (Q ₁₀ = 0.48) and low in Dracunculus vulgaris (Q ₁₀ = 0.74). Switching temperatures were approximately 30, 15 and 20°C, respectively. There were no relationships between precision, switching temperature or maximum respiration rate. High precision reveals a powerful inhibitory mechanism that overwhelms the tendency of temperature to increase respiration. Variability in the shape and position of the respiration–temperature curves must be accounted for in any explanation of the control of respiration in thermoregulatory flowers.     

Biochemical kinetic behaviors between n-butyl acetate and composite bead in biofilter

In this study, the kinetic behaviors between n-butyl acetate and composite bead were investigated. Both microbial growth rate and biochemical reaction rate would be inhibited with increasing average inlet concentration. The order of the inhibitive effect, which resulted from increased average inlet concentration for four operation temperatures, was 30>35>40>25 °C. Both microbial growth rate and biochemical reaction rate would be enhanced and inhibited with increasing operation temperature in the operation temperature ranges of 25 to 30 and 30 to 40 °C, respectively. The enhancing and inhibitive effects resulting from increased operation temperature were the most pronounced at the average inlet concentration of 200 ppm. The values of maximum reaction rate V _m and half-saturation constant K _s ranged from 0.011 to 0.047 g C h⁻¹ kg⁻¹ packed material and from 19.30 to 62.40 ppm, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction kinetic model. The values of maximum elimination capacity ranged from 0.51 to 0.20 g C h⁻¹ kg⁻¹ packed material, and the optimal maximum elimination capacity of biofilter occurred at the operation temperature of 30 °C.     

Enhanced welan gum production using a two-stage agitation speed control strategy in Alcaligenes sp. CGMCC2428

Batch fermentative production of welan gum by Alcaligenes sp. CGMCC2428 was investigated under various oxygen supply conditions using regulating agitation speed. Based on a three kinetic parameters analysis that includes specific cell growth rate (μ), specific glucose consumption rate (q _s), and specific welan formation rate (q _p), a two-stage agitation speed control strategy was proposed to achieve high concentration, high yield, and high viscosity of welan. During the first 22 h, the agitation speed in 7.5 L fermenter was controlled at 800 rpm to maintain high μ for cell growth. The agitation was then reduced step-wise to 600 rpm to maintain a changing profile with stable dissolved oxygen levels and obtain high qp for high welan accumulation. Finally, the maximum concentration of welan was reached at 26.3 ± 0.89 g L⁻¹ with a yield of 0.53 ± 0.003 g g⁻¹ and the welan gum viscosity of 3.05 ± 0.10 Pa s, which increased by an average of 15.4, 15.2, and 20.1% over the best results controlled by constant agitation speeds.     

Temperature dependency of miniature end plate currents from the extraocular muscle of Antarctic teleost fishes

The effects of temperature on the decay phase of post-synaptic currents were examined to determine the extent of temperature compensation in the inferior oblique extraocular muscles of four Antarctic fishes (Trematomus bernacchii, Trematomus pennellii, Trematomus hansoni, and Pagothenia borchgrevinki, Family Nototheniidae). At ambient temperatures, different fish produce miniature end plate currents (MEPCs), which vary in duration and rate of decay. Low temperatures normally prolong MEPCs, however, Antarctic fishes were found to produce MEPCs of significantly shorter duration than predicted (based on back-extrapolation of temperate fish data to sub-zero temperatures). Notothenioid decay time constants were approximately 500 μs faster than their temperate counterparts, extrapolated to −2°C, suggesting that the difference is consistent with temperature compensation in the neural-systems of Antarctic fish. Results presented here conform the hypothesis that post-synaptic MEPCs of Antarctic fish exhibit temperature compensation, an adaptive feature that has permitted the successful radiation throughout the Southern Ocean.     

Diverging climate trends in Mongolian taiga forests influence growth and regeneration of Larix sibirica

Central and semiarid north-eastern Asia was subject to twentieth century warming far above the global average. Since forests of this region occur at their drought limit, they are particularly vulnerable to climate change. We studied the regional variations of temperature and precipitation trends and their effects on tree growth and forest regeneration in Mongolia. Tree-ring series from more than 2,300 trees of Siberian larch (Larix sibirica) collected in four regions of Mongolia’s forest zone were analyzed and related to available weather data. Climate trends underlie a remarkable regional variation leading to contrasting responses of tree growth in taiga forests even within the same mountain system. Within a distance of a few hundred kilometers (140–490 km), areas with recently reduced growth and regeneration of larch alternated with regions where these parameters remained constant or even increased. Reduced productivity could be correlated with increasing summer temperatures and decreasing precipitation; improved growth conditions were found at increasing precipitation, but constant summer temperatures. An effect of increasing winter temperatures on tree-ring width or forest regeneration was not detectable. Since declines of productivity and regeneration are more widespread in the Mongolian taiga than the opposite trend, a net loss of forests is likely to occur in the future, as strong increases in temperature and regionally differing changes in precipitation are predicted for the twenty-first century.     

Effects of climate warming on plant autotoxicity in forest evolution: a case simulation analysis for Picea schrenkiana regeneration

In order to explore how plant autotoxicity changes with climate warming, the autotoxicity of P. schrenkiana needles' water extract, organic extract fractions, and key allelochemical DHAP was systemically investigated at the temperature rising 2 and 4°C based on the data‐monitored soil temperature during the last decade in the stage of Schrenk spruce regeneration (seed germination and seedling growth). The results showed that the criterion day and night temperatures were 12°C and 4°C for seed germination, and 14°C and 6°C for seedling growth, respectively. In the presence of water extract, the temperature rise of 2°C significantly inhibited the germination vigor and rate of P. Schrenkiana seed, and a temperature rise of 4°C significantly increased the inhibition to the seedling growth (P < 0.05). Among the three organic fractions, the low‐polar fraction showed to be more phytotoxic than the other two fractions, causing significant inhibitory effects on the seed germination and growth even at low concentration of 0.1 mg/mL, and the inhibition effect was enhanced as temperature increased. The temperature rise significantly enhanced the promotion effect of DHAP, while the inhibition effect of temperature rise became less important with increasing concentration of DHAP. This investigation revealed that autotoxicity of P. schrenkiana was affected by the climate warming. As expected, it provided an insight into the mechanism and effectiveness of allelopathy in bridging the causal relationship between forest evolution and climate warming.     

Development of reduced-fat mayonnaise using 4αGTase-modified rice starch and xanthan gum

In this study a disproportionating enzyme, 4-α-glucanotransferase (4αGTase), was used to modify the structural properties of rice starch to produce a suitable fat substitute in reduced-fat (RF) mayonnaise. The mayonnaise fat was partially substituted with the 4αGTase-treated starch paste at levels up to 50% in combination with xanthan gum and the physical and rheological properties of the modified RF mayonnaise samples were investigated. All mayonnaises prepared in this study exhibited shear thinning behavior and yield stress. Viscoelastic properties of mayonnaise were characterized using dynamic oscillatory shear test and it was observed that mayonnaises exhibited weak gel-like properties. The magnitude of elastic and loss moduli was also affected by 4αGTase-treated starch concentration and presence of xanthan gum. In relation to microstructure, RF mayonnaise prepared with 3.8 or 5.6 wt% of 4αGTase-treated starch and xanthan gum showed smaller droplets. The use of 5.6 wt% of 4αGTase-treated starch and 0.1 wt% of xanthan gum produced a RF mayonnaise with similar rheological properties and appearances as FF mayonnaise with gum. This study demonstrated a high feasibility for using 4αGTase-treated rice starch as a viable fat replacer in mayonnaise.     

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days. Photosynthetic parameters, photosynthetic efficiency (α), maximum quantum yield (Fv/Fm), maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation. In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C. Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure length. Recovery rates of Fv/Fm ranged from −5.06E−7 ± 2.71E−7 s⁻¹ to 1.36E−5 ± 1.53E−5 s⁻¹ for monthly experiments and from −9.63E−7 ± 7.71E−7 s⁻¹ to 2.65E−5 ± 2.97E−5 s⁻¹ for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E−7 ± 8.11E−7 s⁻¹ to 7.50E−3 ± 7.1E−4 s⁻¹. The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter.     

Kinetic analysis of hybridoma cells viability under mechanical shear stress with and without serum protection

The effect of a well-defined mild shear stress on hybridoma cell viability (HB-8852) in a serum-free culture medium has been analysed, and the role as shear protector of different concentrations of fetal bovine serum have been studied. Samples harvested from cultures in their late exponential growth phase, were subjected in a rheometer to a constant shear stress of 0.41 ± 0.02 Pa, and the evolution of viable and total cell concentrations was determined and compared with static controls. A simple segregated kinetic model for the viable and dead cells was used to know the effect of serum concentration on the specific cell growth and death rate of the cells.     

Effects of cold stress on metabolic regulation in the overwintering larvae of the Chinese white pine beetle,Dendroctonus armandi

The Chinese white pine beetle, Dendroctonus armandi Tsai & Li (Coleoptera: Curculionidae, Scolytinae), is considered the most destructive forest pest in the Qinling and Bashan Mountains of China. In recent years, winter temperature has dropped in these regions, and extremely low temperatures are hard to survive for insects. Cold hardiness becomes a crucial strategy because temperature change often leads to fluctuations in insect abundance, and the metabolism rate is a key index of resistance to cold in overwintering insects. Therefore, we investigated the relationship between the change in respiratory rate and the activity of metabolism-related mitochondrial enzymes in D. armandi larvae under cold conditions. We found that the respiratory rate decreased, and it was matched with the activity of glutamate dehydrogenase, aconitase, and lipase during overwintering. Among the various test times under cold conditions, the respiratory rate also decreased with decreasing temperature and increased under very low temperatures. At all cold stress periods, glutamate dehydrogenase and lipase showed increased activity at higher temperatures and decreased activity under lower temperatures, but the activity of NAD-malic enzyme, NADP-malic enzyme, mitochondrial isocitrate dehydrogenase, and aconitase were contrary. Under all low temperatures, the activity of enzymes – except for NADP-malic enzyme, glutamate dehydrogenase, and lipase – increased in short-term cold stress and decreased in long-term cold stress at 4, 0, −4, −6, −8, and −10 °C. However, at −2 °C, the activity of enzymes showed a decreasing trend in short-term treatments and an increasing trend in long-term treatments, except for mitochondrial isocitrate dehydrogenase. The results not only improve our understanding of the metabolic mechanism of cold adaptation in D. armandi, but also provide an important experimental basis for further study and biological pest control.     

Quantifying the heterogeneous heat response of Escherichia coli under dynamic temperatures

Aims: Non‐sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (T_max) were previously explained by the coexistence of two subpopulations, i.e. a stress‐sensitive and a stress‐resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing T_max, is studied. Methods and Results: Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h^?1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known T_max. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well. Conclusions: This study further confirms the existence of a stress‐resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than T_max. Significance and Impact of the Study: The growth of the small stress‐resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies.     

Different effects of night versus day high temperature on rice quality and accumulation profiling of rice grain proteins during grain filling

High temperature has adverse effects on rice yield and quality. The different influences of night high temperature (NHT) and day high temperature (DHT) on rice quality and seed protein accumulation profiles during grain filling in indica rice ‘9311’ were studied in this research. The treatment temperatures of the control, NHT, and DHT were 28°C/20°C, 27°C/35°C, and 35°C/27°C, respectively, and all the treatments were maintained for 20 days. The result of rice quality analysis indicated that compared with DHT, NHT exerted less effect on head rice rate and chalkiness, whereas greater effect on grain weight. Moreover, the dynamic accumulation change profiles of 61 protein spots, differentially accumulated and successfully identified under NHT and DHT conditions, were performed by proteomic approach. The results also showed that the different suppressed extent of accumulation amount of cyPPDKB might result in different grain chalkiness between NHT and DHT. Most identified isoforms of proteins, such as PPDK and pullulanase, displayed different accumulation change patterns between NHT and DHT. In addition, compared with DHT, NHT resulted in the unique accumulation patterns of stress and defense proteins. Taken together, the mechanisms of seed protein accumulation profiles induced by NHT and DHT during grain filling should be different in rice, and the potential molecular basis is discussed in this study.     

Analysis of cDNA libraries from developing seeds of guar (<Emphasis Type="Italic">Cyamopsis tetragonoloba</Emphasis>(L.) Taub)

Background  

Guar, Cyamopsis tetragonoloba (L.) Taub, is a member of the Leguminosae (Fabaceae) family and is economically the most important of the four species in the genus. The endosperm of guar seed is a rich source of mucilage or gum, which forms a viscous gel in cold water, and is used as an emulsifier, thickener and stabilizer in a wide range of foods and industrial applications. Guar gum is a galactomannan, consisting of a linear (1→4)-β-linked D-mannan backbone with single-unit, (1→6)-linked, α-D-galactopyranosyl side chains. To better understand regulation of guar seed development and galactomannan metabolism we created cDNA libraries and a resulting EST dataset from different developmental stages of guar seeds.     

Evaluation of <Emphasis Type="BoldItalic">Sterculia foetida</Emphasis> Gum as Controlled Release Excipient

The purpose of the research was to evaluate Sterculia foetida gum as a hydrophilic matrix polymer for controlled release preparation. For evaluation as a matrix polymer; characterization of Sterculia foetida gum was done. Viscosity, pH, scanning electronmicrographs were determined. Different formulation aspects considered were: gum concentration (10–40%), particle size (75–420 μm) and type of fillers and those for dissolution studies; pH, and stirring speed were considered. Tablets prepared with Sterculia foetida gum were compared with tablets prepared with Hydroxymethylcellulose K15M. The release rate profiles were evaluated through different kinetic equations: zero-order, first-order, Higuchi, Hixon-Crowell and Korsemeyer and Peppas models. The scanning electronmicrographs showed that the gum particles were somewhat triangular. The viscosity of 1% solution was found to be 950 centipoise and pH was in range of 4–5. Suitable matrix release profile could be obtained at 40% gum concentration. Higher sustained release profiles were obtained for Sterculia foetida gum particles in size range of 76–125 μm. Notable influences were obtained for type of fillers. Significant differences were also observed with rotational speed and dissolution media pH. The in vitro release profiles indicated that tablets prepared from Sterculia foetida gum had higher retarding capacity than tablets prepared with Hydroxymethylcellulose K15M prepared tablets. The differential scanning calorimetry results indicated that there are no interactions of Sterculia foetida gum with diltiazem hydrochloride. It was observed that release of the drug followed through surface erosion and anomalous diffusion. Thus, it could be concluded that Sterculia foetida gum could be used a controlled release matrix polymer.     

Biosorption of Ni (II) by Schizosaccharomyces pombe: kinetic and thermodynamic studies

The potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake of Ni(II) on S. pombe, q _e, was obtained at 25 °C as 33.8 mg g⁻¹. It decreased with increasing temperature within a range of 25–50 °C denoting an exothermic behaviour. Increasing initial Ni(II) concentration up to 400 mg L⁻¹ also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L⁻¹. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich–Peterson, and Kahn isotherm equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature. Gibbs free energy changes (ΔG°) of the system at 25, 30, 35 and 50 °C were found as −1.47E + 4, −1.49E + 4, −1.51E + 4, and −1.58E + 4 J mol⁻¹, respectively. Enthalpy change (ΔH°) was determined as −2.57E + 3 J mol⁻¹ which also supports the observed exothermic behaviour of the biosorption process. Entropy change (ΔS°) had a positive value (40.75 J mol⁻¹ K⁻¹) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed to act as a separating agent for Ni(II) recovery from its aqueous solution.