Formation Of Insoluble Complexes Research Articles

GEMAS: Phosphorus in European agricultural soil - sources versus sinks at the continental-scale - the geological perspective

Phosphorus (P) is one of the essential elements for life on Earth. As a major nutrient it is needed for healthy growth both in plants and living organisms. Although the abundance of P in the Earth's upper continental crust is relatively high (655 mg/kg), many soil types are poor in available phosphorus. The main natural factors controlling the availability of P in soil are pH, mineralogy, and formation of insoluble complexes with Al and Fe under acidic, and with Ca and Mg under alkaline soil conditions. Superimposed weathering processes and climate contribute strongly to P mobility and availability. Additionally, a large fraction of total soil P is in organic forms, which are not directly available to plants. Phosphorus is a major component in fertilisers and thus a significant source of anthropogenic P in soil and water.In the agricultural soil samples that were collected during the Geochemical Mapping of Agricultural and grazing land Soil (GEMAS) project, the total P concentrations (XRF, median 786 m/kg) are only slightly higher than those extracted by hot aqua regia (AR, median 653 mg/kg), while the median concentration in the weak MMI® cold extraction is as low as 4.1 mg/kg. The AR results show very low P concentrations over the coarse-grained sandy sediments of the last glaciation in central and northern Europe and in calcareous soil. The southern limit of the last glaciation is visible as a concentration break on the geochemical maps. In general, north-eastern and north-western Europe are marked by high P values, probably related to cold and humid climate and enrichment in humus-rich coastal soil. The spatial distribution of P at the continental-scale is dominated by geogenic and climatic factors, and the anthropogenic influence is difficult to assess and quantify.

Effects of wollastonite and phosphate treatments on cadmium bioaccessibility in pak choi (Brassica rapa L. ssp. chinensis) grown in contaminated soils.

Cadmium (Cd) contamination of soil can strongly impact human health through the food chain due to uptake by crop plants. Inorganic immobilizing agents such as silicates and phosphates have been shown to effectively reduce Cd transfer from the soil to cereal crops. However, the effects of such agents on total Cd and its bioaccessibility in leafy vegetables are not yet known. Pak choi (Brassica rapa L. ssp. chinensis) was here selected as a representative leafy vegetable to be tested in pots to reveal the effects of silicate-phosphate amendments on soil Cd chemical fractions, total plant Cd levels, and plant bioaccessibility. The collected Cd contaminated soil was mixed with control soil at 1:0, 1:1, 1:4, 0:1 with a view to Cd high/moderate/mild/control soil samples. Three heavy metal-immobilizing agents: wollastonite (W), potassium tripolyphosphate (KTPP), and sodium hexametaphosphate (SHMP) were added to the soil in order to get four different treatment groups, i.e., control (CK), application of wollastonite alone (W), wollastonite co-applied with KTPP (WKTPP), application of wollastonite co-applied with SHMP (WSHMP) for remediation of soils with different levels of Cd contamination. All three treatments increased the effective bio-Cd concentration in the soils with varying levels of contamination, except for W under moderate and heavy Cd contamination. The total Cd concentration in pak choi plants grown in mildly Cd-contaminated soil was elevated by 86.2% after WKTPP treatment compared to the control treatment could function as a phytoremediation aid for mildly Cd-contaminated soil. Using an in vitro digestion method (physiologically based extraction test) combined with transmission electron microscopy, silicate and phosphorus agents were found to reduce the bioaccessibility of Cd in pak choi by up to 66.13% with WSHMP treatment. Application of silicate alone reduced soil bio-Cd concentration through the formation of insoluble complexes and silanol groups with Cd, but the addition of phosphate may have facilitated Cd translocation into pak choi by first co-precipitating with Ca in wollastonite while simultaneously altering soil pH. Meanwhile, wollastonite and phosphate treatments may cause Cd to be firmly enclosed in the cell wall in an insoluble form, reducing its translocation to edible parts and decreasing the bioaccessibility of Cd in pak choi. This study contributes to the mitigation of Cd bioaccessibility in pak choi by reducing soil Cd concentration through in situ remediation and will help us to extend the effects of wollastonite and phosphate on Cd bioaccessibility to other common vegetables. Therefore, this study thus reveals effective strategies for the remediation of soil Cd and the reduction of Cd bioaccessibility in crops based on two indicators: total Cd and Cd bioaccessibility. Our findings contribute to the development of methods for safer cultivation of commonly consumed leafy vegetables and for soil remediation.

Isolation of Phosphate Solubilizing Fungi from Soil and Their Application in Plant Growth Promotion

Phosphorus plays a significant role in numerous physiological and metabolic processes in plants. Soil phosphorus is immobilized due to the formation of insoluble complexes. The use of efficient phosphate-solubilizing microorganisms opens up a new prospect for better crop productivity and for greater yield performance without affecting the soil health. Phosphate-solubilizing fungi (PSF) enhance available phosphorus released from soil, which contributes to P requirement of plants. Hence, the present study was designed to evaluate the utilization of PSF as a biofertilizer. Pikovskaya's Agar medium was used to isolate fungal species from compost and open dumpsite soil. Isolated fungi were labelled as PSF-X, PSF-Y, and PSF-Z. A pot experiment was carried out to determine the effect of isolated fungal strains. The isolated fungal strain was introduced to the developed potting media which contained compost and soil at 1:1 ratio. Soya bean was selected as the experimental plant. Plant growth parameters (shoot length and root length) were measured to determine the effect of isolated fungal strains. Plant growth parameters were recorded after 21days. Fungi inoculated pots showed a significant increase in both shoot and root lengths in comparison to the control (n=9, p<0.05). Potting media consisting of PSF-X showed the best result. The highest root length (4.7±0.1 cm) and shoot length (35.8±1.2 cm) were recorded in pots inoculated with PSF-
 
 Hence, isolated PSF-X, PSF-Y, and PSF-Z are recommended as suitable biofertilizer strains for potting medium.
 
 
 Keywords: Fertilizer, Fungi strain, Phosphorus, Plant growth

Interplay of Drug-Polymer Interactions and Release Performance for HPMCAS-Based Amorphous Solid Dispersions.

The interplay between drug and polymer chemistry and its impact on drug release from an amorphous solid dispersion (ASD) is a relatively underexplored area. Herein, the release rates of several drugs of diverse chemistry from hydroxypropyl methylcellulose acetate succinate (HPMCAS)-based ASDs were explored using surface area normalized dissolution. The tendency of the drug to form an insoluble complex with HPMCAS was determined through coprecipitation experiments. The role of pH and the extent of drug ionization were probed to evaluate the role of electrostatic interactions in complex formation. Relationships between the extent of complexation and the drug release rate from an ASD were observed, whereby the drugs could be divided into two groups. Drugs with a low extent of insoluble complex formation with HPMCAS tended to be neutral or anionic and showed reasonable release at pH 6.8 even at higher drug loadings. Cationic drugs formed insoluble complexes with HPMCAS and showed poor release when formulated as an ASD. Thus, and somewhat counterintuitively, a weakly basic drug showed a reduced release rate from an ASD at a bulk solution pH where it was ionized, relative to when unionized. The opposite trend was observed in the absence of polymer for the neat amorphous drug. In conclusion, electrostatic interactions between HPMCAS and lipophilic cationic drugs led to insoluble complex formation, which in turn resulted in ASDs with poor release performance.

Base free HMF oxidation over Ru-MnO2 catalysts revisited: Evidence of Mn leaching to Mn-FDCA complexation and its implications on catalyst performance

2,5-furandicarboxylic acid (FDCA) is a high value bio-based chemical useful for the production of next generation renewable polymers, epoxy-resins and surfactants. Herein, we show that the performance and stability of MnO2 based oxidation catalysts used in FDCA production are considerably influence by process conditions (especially initial HMF conc. and presence of base additives). Although, base free aerobic oxidation of HMF to FDCA is known to be highly effective over Ru modified MnO2 catalysts, our experiments showed considerable leaching of MnO2 phase under reaction conditions with the formation of insoluble Mn-FDCA complexes. The formation of Mn-FDCA complex and Mn leaching was also supported by control experiments between FDCA and various Mn oxides under hydrothermal conditions and its structure confirmed by single crystal XRD. Formation of Mn-FDCA and Mn leaching was also identified as the underlying reason for carbon balance deficit, catalyst mass loss and deactivation observed upon reuse.

Binding and Specificity of Ovalbumin with Chitosan Derivatives Varying in Degree of Acetylation

Here is an insight into the interaction and formation of insoluble complexes of ovalbumine (OV) with a series of specific chitosan derivatives (oligochitosan (OCHI)), varying in the degree of acetylation (DA) in acidic, neural and alkaline media. The forces involved in the complexation are determined and discussed. As shown, the interaction is partially electrostatic by nature with the “molar” composition in the insoluble OCHI-25/OV and OCHI-31/OV complexes of 1:2.8 and 1:2.1, respectively. The interaction is also partially hydrophobic and intensified at elevated temperatures. It is found that the binding of OV to OCHI and stability of the complexes depend on the way they are formed, and the affinity of OV to OCHI weakens with the increase in the DA. The complexes formed in a slightly acidic solution are limitedly soluble at a high solution ionic strength, and the aggregative state of the complexes depends on the weight fraction of OCHI in the complexes. The finding can be useful for understanding the complexation processes of chitosan with proteins and can be promising as a platform for the preparation of ovalbumin-based vaccines.

Effect of pH on the gelling properties of pea protein-pectin dispersions

Phase behavior of protein-polysaccharide mixtures can be controlled by adjusting parameters, such as polymer concentrations and pH. However, the relationships between these interactions and resulting microstructures and textures are not fully understood. The effects of pH (5.5, 7, and 8.5) and low-methoxyl (LM) pectin content (0.5% and 1%) on the rheological properties and microstructures of heat-induced pea protein gels were investigated. At pH 5.5, the addition of LM pectin significantly increased the size of protein aggregates, which is explained by the strong interactions between proteins and LM pectins at that pH; a quartz crystal microbalance revealed the formation of insoluble complexes with reduced solubility. The storage modulus (G′) of pea protein gels at pH 5.5 increased with 0.5% of LM pectin, whereas 1% of LM pectin led to a decreased G′ and the gels water holding capacity. At pHs 7 and 8.5, the addition of LM pectin increased the size of protein aggregates due to the segregative phase separation of negatively charged pea proteins and LM pectins. An increase in G′ with LM pectin concentrations in the gels was also observed at pHs 7 and 8.5. Gel microstructures with phase-separated zones were observed by confocal microscopy. Furthermore, the addition of LM pectin increased the digestibility of pea protein gels prepared at the three pH values under simulated gastrointestinal conditions. Better knowledge of the rheological properties and microstructures of pea protein-LM pectin mixed gels obtained under different pH conditions will allow for optimal use of protein-polysaccharide mixtures in food formulations to attain binary gel products with expected textural and nutritional properties.

Soluble phenols in litter are reduced during passage through the soil macrofauna gut due to the formation of insoluble complexes with proteins: A case study with isopods and Diptera larvae

Plant litter represents a major source of soil organic matter and hence understanding the pathway of its decomposition and stabilisation is crucial for understanding the soil carbon dynamic. Importantly, more than half of annual litter production is consumed by soil fauna globally. Here we test the hypothesis that soluble phenols can be removed from the litter during gut passage and bound on nitrogen rich compounds, which results in formation of insoluble complexes in the faeces produced by soil fauna. Two invertebrate species, Diptera larvae Bibio marci and terrestrial isopod Armadilidium vulgare, and litter of two tree species, Quercus robur and Alnus glutinosa, were used. Both species of invertebrates were fed by both litter types in full factorial manner. The litter contained significantly more free phenols than the faeces. In opposite, the content of bound phenols was significantly higher in faeces than in the litter. The loss of total nitrogen associated with removal of bound phenolic compounds from faeces was higher than that of the litter. Thus, soil fauna contributes to the stabilisation of soil organic matter by the conversion of soluble phenols to insoluble ones together with nitrogen immobilization. In conclusion, this process of stabilisation likely plays an important role in mature soils where mineral surfaces have reached carbon saturation or in soils with higher organic horizons.

Multilayered regulation of iron homeostasis in Arabidopsis.

Iron (Fe) is an essential micronutrient for plant growth and development due to its role in crucial processes such as photosynthesis and modulation of the redox state as an electron donor. While Fe is one of the five most abundant metals in the Earth's crust, it is poorly accessible to plants in alkaline soils due to the formation of insoluble complexes. To limit Fe deficiency symptoms, plant have developed a highly sophisticated regulation network including Fe sensing, transcriptional regulation of Fe-deficiency responsive genes, and post-translational modifications of Fe transporters. In this mini-review, we detail how plants perceive intracellular Fe status and how they regulate transporters involved in Fe uptake through a complex cascade of transcription factors. We also describe the current knowledge about intracellular trafficking, including secretion to the plasma membrane, endocytosis, recycling, and degradation of the two main Fe transporters, IRON-REGULATED TRANSPORTER 1 (IRT1) and NATURAL RESISTANCE ASSOCIATED MACROPHAGE PROTEIN 1 (NRAMP1). Regulation of these transporters by their non-Fe substrates is discussed in relation to their functional role to avoid accumulation of these toxic metals during Fe limitation.

Interplay between soluble and insoluble protein/calcium/phytic acid complexes in dispersions of faba bean and pea protein concentrates around neutral pH

Pulses are rich in proteins and a good source of calcium. However, antinutritional compounds such as phytic acid can bind to proteins and minerals to form complexes, reducing their digestibility and bioavailability, respectively. This study investigated interactions and potential complex formation between phytic acid, calcium, and proteins in pea and faba bean concentrate dispersions. The solubility of the 3 compounds was measured at pH 6.5, 7.0 and 7.5. Formation of complexes was investigated by chelating calcium upon EDTA addition or by removing proteins via ultrafiltration. Protein profiles were compared using Size Exclusion Chromatography (SEC). For both pea and faba bean, protein solubility increased with increasing pH. Phytic acid solubility was minimum at pH 7.0, while simultaneously calcium solubility was maximum. Protein solubility increased with EDTA addition compared to the control at pH 6.5 (pea and faba bean) and 7.0 (pea), supporting the presence of insoluble binary complexes between calcium and proteins. The concomitant rise in phytic acid solubility for pea (pH 6.5 and 7.0) highlighted the formation of either insoluble binary (phytic acid to calcium) or ternary complexes. Also, the formation of soluble protein complexes with phytic acid and, possibly, with calcium was highlighted. Small amounts of soluble ternary complexes were observed at pH 7.5. SEC results showed an increase in globulin's (especially legumin) solubility after calcium chelation; this demonstrated the formation of insoluble complexes mediated by calcium. This study highlighted that the different protein fractions from pulses must be considered separately in their ability to establish complexes with calcium and phytic acid.

Unraveling the potential health impact of the interactions between pea hydrolysates/peptides originating under gastric digestion and bile salts

Bile salts (BS) are biological surfactants that have important physiological functions mainly by participating in lipid digestion and intervening in the transport, absorption, and excretion of hydrophobic products. Bile salts have been shown to interact with the products of protein hydrolysis, being this interaction a key point to modulate several physiological processes.The type and size of peptides, released at different times of gastric digestion, could have different implications in these physiological processes modulated by the BS. In the present study we focused on understanding how the interactions of hydrolysates/peptides from native or commercial pea protein isolates with BS (formation of insoluble complexes or the modification of the BS micellar solubilization of poorly soluble molecules) evolve according to their residence time in a static gastric digestion model. The different residence times (10–60 min) would simulate different emptying points in which the partially hydrolyzed pea proteins by pepsin in the stomach are flushed into the duodenum and come into contact with the BS.It is observed that the longer residence times in the stomach the degree of hydrolysis of the pea isolates is greater, producing an increase in the soluble fraction. Both isolates showed a slight tendency to bind BS and form insoluble precipitates. The interaction of the soluble fraction of pea protein hydrolysates with the BS micelles, acted synergistically, increasing the solubilization capacity of oleic acid, taken as a model molecule.Likewise, it is shown that the structural changes of pea proteins due to processing have a profound influence on the interaction with BS and potentially affect the physiological reactions that they modulate.

Formation and microstructural characterization of scallop (Patinopecten yessoensis) male gonad hydrolysates/sodium alginate coacervations as a function of pH

Studying the noncovalent interactions between proteins and polysaccharides is quite important mainly due to the wide number of applications such as developing pH-responsive complexes. Scallop Patinopecten yessoensis male gonad hydrolysates‑sodium alginate (SMGHs-SA) was investigated as noncovalent complexes at pH from 1 to 10. The critical pH values pHC (around 6) and pHφ (around 4) were independent of the SMGHs-SA ratio, indicating the formation of soluble and insoluble complexes. The pH response of SMGHs-SA complexes was evaluated by investigating the rheological behavior, moisture distribution, functional group change and microstructure. Compared to the co-soluble and soluble complexes phases, the SMGHs-SA complexes had a higher storage modulus and viscosity as well as a lower relaxation time (T23) in the insoluble complexes phase (pHφ>3). Additionally, the amide I band and COO− stretching vibration peaks were redshifted and the amide A band vibration peaks were blueshifted by acidification. Electrostatic interactions and intermolecular/intramolecular hydrogen bonding led to SMGHs-SA agglomeration at pH 3, forming a uniform and dense gel network structure with strong gel strength and water-retention capacity. This study provides a theoretical and methodological basis for the design of novel pH-responsive complexes by studying SMGHs-SA complex coacervation.

Heteroprotein complex coacervation of ovalbumin and lysozyme: Phase behavior, microstructure and processing properties

Egg white protein is a complex network system formed by the aggregation and interaction of multiple proteins, in which two oppositely charged proteins can induce the formation of heteroprotein complex coacervate (HPCC). This investigation aims to probe the complexation between ovalbumin (OVA) and lysozyme (LYS) via the heteroproteins phase diagram model, exploring the relationship between differential processing properties and complex state, protein molecular structure and intermolecular interactions. Results showed that the characteristic pH (pHc, pHɸ1, pHmax, pHɸ2) intensely relied on the protein ratios. Consequences of ζ-potential and the phase diagram manifested that OVA-LYS complex formation was predominantly triggered by electrostatic interactions. With the increasing OVA-LYS mixing ratio, the characteristic pH of the complex moved towards a higher pH value. By comparing the microphase structure of different phase regions induced by pH, we found that the protein structure unfolded at low pH, elevating the foaming and emulsifying capacity. Moreover, further increases in pH value brought on larger insoluble complex formation, which enhanced the foaming stability while decreased the emulsifying stability. Noteworthy, the coacervates obtained in the narrow range of pH 6.5–9.5 presented the strongest gel strength and highest water holding capacity, which was considered to be an efficacious way to regulate the gel properties of egg white protein. On the whole, the findings of this paper developed prominent insight for understanding the interaction between heteroproteins, which would lay a theoretical foundation for improving the quality and efficiency of functional egg powder and product development.

Effect of Soft Preheating of Bovine Serum Albumin on the Complexation with Oligochitosan: Structure and Conformation of BSA in the Complex.

Phase analysis, spectroscopic and light scattering methods are applied to investigate the peculiarities of the interaction of oligochitosan (OCHI) with native and preheated BSA as well as the conformational and structural changes of BSA in BSA/OCHI complex. As shown, untreated BSA binds with OCHI mainly forming soluble electrostatic nanocomplexes, with the binding causing an increase in BSA helicity without a change in the local tertiary structure and thermal stability of BSA. In contrast, soft preheating at 56°C enhances the complexation of BSA with OCHI and slightly destabilizes the secondary and local tertiary structures of BSA within the complex particles. Preheating at 64°C (below the irreversible stage of BSA thermodenaturation) leads to further enhancement in the complexation and formation of insoluble complexes stabilized by both Coulomb forces and hydrophobic interactions. The finding can be promising for the preparation of biodegradable BSA/chitosan-based drug delivery systems. This article is protected by copyright. All rights reserved.

Formation mechanism of complex coacervation of chayote (Sechium edule) pectin-sodium caseinate in aqueous solution

Chayote (Sechium edule) is a kind of vegetable with high economic value, and its pectin has potential application in processed food. In this study, the phase behavior, turbidity, Zeta-potential, rheological behavior, FTIR, microstructure, and thermal properties were used to investigate the complex coacervation of the chayote pectin (CP) and sodium caseinate (CAS) in aqueous solution, with apple pectin as the control. The results showed that the impact of pHs and CAS-CP mixing ratios on phase behavior was comparable to apple pectin. When the pH value was above CAS's isoelectric point (Ip4.6), there were mainly hydrogen bonding and hydrophobic interaction between CAS and CP, forming a soluble complex. In contrast, the formation of insoluble complexes was driven by electrostatic attraction when the pH was below Ip4.6. The formation of complexes shifted towards lower pH as CP addition increased. The CAS-CP mixture fluid had shear thinning property. There was the greatest electrostatic attraction between CAS and CP at pH 3.5. At the same time, the secondary structure of CAS may have changed during the formation of the complexes. The complexes formed by CAS and CP had good thermal properties. The results of this study provided a theoretical basis for applying CP as a novel raw material in food processing.

Formation and physicochemical properties of insoluble complexes resulted from high methoxyl pectin – protein interactions

The present work studied the complex coacervation of high methoxyl pectin (HMP) with three proteins [Whey protein isolate (WPI), Sodium caseinate (SC) or pea protein isolate (PPI)] during acidification. Each protein and HMP were mixed at various ratios (1:1 to 10:1) with the sum of their concentrations ranging from 0.2 to 1.1%. Complex coacervate formation, as investigated by phase diagrams and zeta potential measurements, depended on the protein and the strength of the electrostatic protein-HMP interactions. Οptimum coacervation was achieved at 6:1 mixing ratio and at pH 4 for SC and WPI or pH 3 for PPI. The complexes formed at these conditions were isolated and studied further in terms of their colour, moisture content, solubility, pH, conductivity, kinematic viscosity, density, porosity, flowability and cohesiveness. Their behaviour differed from the behaviour of their constituents. Overall, the mixtures with PPI differed from the remaining mixtures not only in their phase behaviour but also on the properties of their complexes. This deviation was attributed to weaker attractive forces between HMP and PPI. The results of the present study can be useful for the modulation of HMP based biopolymer complexes and their exploitation as structuring or encapsulating agents in food matrices.

A new class of monoclonal Aβ antibodies selectively targets and triggers deposition of Aβ protofibrils.

Aggregation and accumulation of amyloid-β peptide (Aβ) are a critical trigger for the onset of Alzheimer's disease (AD). While the plaques are the most outstanding Aβ pathological feature, much of the recent research emphasis has been on soluble Aβ species because of their diffusible, proinflammatory, and toxic properties. The focus on soluble aggregated Aβ species has also increased the interest in antibodies that are selective for different Aβ conformations. In the current study, we developed and characterized a new class of monoclonal antibodies (referred to as mAbSL) that are selective for Aβ protofibrils. Cloning and sequencing of the heavy and light chain variable regions for multiple antibodies identified sequence characteristics that may impart the conformational selectivity by the antibodies. Transfection of FreeStyle 293F cells with the plasmids permitted in-house expression and purification of mAbSL antibodies along with non-conformation-selective Aβ monoclonal antibodies (Aβ mAbs). Several of the purified mAbSL antibodies demonstrated significant affinity and selectivity for Aβ42 protofibrils compared with Aβ42 monomers and Aβ42 fibrils. Competition ELISA assays assessing the best overall antibody, mAbSL 113, yielded affinity constants of 7 nM for the antibody-Aβ42 protofibril interaction, while the affinity for either Aβ42 monomers or Aβ42 fibrils was roughly 80 times higher. mAbSL 113 significantly inhibited Aβ42 monomer aggregation by a unique mechanism compared with the inhibition displayed by Aβ mAb 513. Aβ42 protofibril dynamics were also markedly altered in the presence of mAbSL 113, whereby insoluble complex formation and protofibril deposition were stimulated by the antibody at low substoichiometric molar ratios. As the field contemplates the therapeutic effectiveness of Aβ conformation-selective antibodies, the findings presented here demonstrate new information on a monoclonal antibody that selectively targets Aβ protofibrils and impacts Aβ dynamics.

A longer biodegradation process enhances the cadmium adsorption of the biochar derived from a manure mix

Adsorption of heavy metals by biochar adsorbents can reduce their bioavailability and mobility. However, the effects of the biodegradation processes of raw material before biochar preparation on adsorption remain unclear. This study utilized the degradation products at different stages of the compost to produce biochars and investigated their adsorption property. Compared to the virgin biochar (IBC) prepared from untreated compost, the biochar (EBC and LBC) prepared from the sample collected by the biodegradation process had more robust adsorption properties. Furthermore, the adsorption capacity of biochar (LBC) prepared from the sample collected in the later biodegradation process was approximately 50% higher than that of biochar (EBC) prepared from the sample collected in the early phase. LBC had more oxygen-containing functional groups, more ion exchange sites, and carbonate ions, improving the adsorption capacity by 100% compared with IBC. The BET surface area of LBC was approximately four times higher than that of IBC and 25% more than EBC. Moreover, the dominant adsorption mechanism of LBC is the formation of insoluble Cd-mineral complexes (cadmium carbonate) with the inorganic. The increase in pH also facilitated Cd (II) precipitation. This study highlighted that appropriate biodegradation before biochar preparation from manure mix is an effective and energy-saving method to enhance the ability of biochar to adsorb heavy metals.

Regulation of Intersubunit Interactions in Homotetramer of Glyceraldehyde-3-Phosphate Dehydrogenases upon Its Immobilization in Protein-Kappa-Carrageenan Gels.

Polysaccharides, being biocompatible and biodegradable polymers, are highly attractive as materials for protein delivery systems. However, protein-polysaccharide interactions may lead to protein structural transformation. In the current study, we analyze the structural adjustment of a homotetrameric protein, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), upon its interactions with both flexible coil chain and the rigid helix of κ-carrageenan. FTIR spectroscopy was used to probe the secondary structures of both protein and polysaccharide. Electrostatically driven protein-polysaccharide interactions in dilute solutions resulted in an insoluble complex formation with a constant κ-carrageenan/GAPDH ratio of 0.2, which amounts to 75 disaccharide units per mole of protein tetramer. Upon interactions with both coiled and helical polysaccharides, a weakening of the intersubunit interactions was revealed and attributed to a partial GAPDH tetramer dissociation. In turn, protein distorted the helical conformation of κ-carrageenan when co-gelled. Molecular modeling showed the energy favorable interactions between κ-carrageenan and GAPDH at different levels of oligomerization. κ-Carrageenan binds in the region of the NAD-binding groove and the S-loop in OR contact, which may stabilize the OP dimers. The obtained results highlight the mutual conformational adjustment of oligomeric GAPDH and κ-carrageenan upon interaction and the stabilization of GAPDH's dissociated forms upon immobilization in polysaccharide gels.

Enhanced large-scale production of recombinant phytase in E. coli DH5 α: Medium components optimization and thermodynamic studies

Medium components and their solubility for improvement of recombinant phytase production in Escherichia coli DH5α. was optimized and reported in this study. Solubility study was supported by the computational works conducted using COSMO-RS, a quick tool to predict the thermophysical and chemical properties of fluid mixture. Solubility concept through thermodynamic calculation was introduced to study the interaction between medium components with water and selected medium components with each other. Based on the σ-profile and σ-potential, together with Gibbs free energy, a less soluble medium component showed a negative effect on phytase production due to the formation of insoluble metal-ion phytate complexes. Highest phytase production was obtained under optimum conditions of as 30 g/L yeast extracts, 1 g/L (NH4)2HPO4, 3 g/L MgSO4·7H2O, 0.3 g/L FeSO4·7H2O and 0.1 % (v/v) glycerol. Both experimental and computational works were conducted to investigate the interaction between medium components. The melting point and phase appearance of the mixture were studied. From experimental results, the mixtures were seemed to be unstable due to its higher melting point compared to individual medium components. The analysis from Gibbs free energy reflected the total immiscibility between medium components. It was concluded that medium components worked individually to promote the phytase production. Yeast extract, MgSO4·7H2O and FeSO4·7H2O were selected for optimization by central composite design, whereas other factors were maintained at their optimal level. Statistical analysis showed that the optimum media containing 34.06 g/L yeast extract, 3.6 g/L MgSO4·7H2O and 0.32 g/L FeSO4·7H2O gave the maximum phytase production of 118.91 U/mL. The optimization of process condition such as temperature, agitation speed and seed age were further investigated by employing Full Factorial Experimental (FUFE) Design after fixing the media composition. The maximum phytase production of 200 U/mL was obtained at optimum condition (temperature 37 °C, agitation speed 500 rpm and seed age 1.55 at OD600nm). The phytase production in a larger scale was conducted by submerged fermentation in 2 L and 30 L bioreactor. In large scale production, constant tip speed suited the best for scale-up strategy comparing to the constant power number. The optimum process condition improved the phytase production and plasmid stability.