Retrogradation and Gel Textural Attributes of Corn Starch Amylose and Amylopectin Fractions

An understanding of relationships between starch molecular structure and function could increase the opportunity to develop additional uses for starch. Using a combined aqueous (aq.) leaching and alcohol precipitation technique, six amylose fractions were obtained from regular and two high amylose (hAM) corn starches (50 and 70%). Five amylopectin fractions were obtained from regular and waxy corn starches. After freeze-drying the fractions, high performance size exclusion chromatography (HPSEC) was used to estimate weight-average (M_w) and number-average (M_n) molecular weights, and to determine polydispersity (M_w/M_n) and purity. Increase in fraction reducing power after pullulanase treatment was determined and expressed as a relative index of branching. Amylose-fractions showed varying but similar (P>0·05) M_w(1·40–5·68E+05), similar polydispersities (2·1–2·9), and branching values (1·93E-04–4·14E-05). Amylose branching increased with decreasing M_w. Amylopectin had varying M_w(2·88–5·43E+07) and similar polydispersities (1·3–1·5), but different branching values (7·30E-04–1·54E-03), that did not follow any M_worder. Fraction melting temperatures, enthalpies, and gel retrogradation behaviours were determined using differential scanning calorimetry (DSC). No enthalpies were observed for amylose fractions. Amylopectin fractions with high branching values that had intermediate to low M_w(3·75–2·88E+07), showed marked retrogradation. Enthalpy was correlated neither to branching nor M_w. Gel textural profile analysis (fracturability, adhesive force, cohesiveness, and springiness) showed that for amylose, intermediate M_wfractions promoted less fracturability, while adhesive force, and stringiness increased with a decrease in M_w. For amylopectin, the intermediate M_wand highly branched fractions reduced fracturability, and promoted adhesive force, and stringiness. Amylopectin fractions of intermediate M_wand high extent of branching underwent increased retrogradation. Amylose gel textural attributes were governed by molecular weight, while molecular weight and branching governed amylopectin gel textural properties.     

Microwave-enhanced alkali treatment of Pinus yunnanensis: Physiochemical characterization of the dissolved lignins

Pinus yunnanensis was subjected to water-bath and microwave treatments in 1% NaOH aqueous solutions at 100 °C with various ratios of bath heating time to microwave heating time (0/120, 20/100, 40/80, 60/60, 80/40, 100/20 and 120/0 min). The lignins dissolved in the alkali liquors were separated and purified, and their physicochemical features were comparatively characterized by sugar analysis, GPC, FT-IR, ¹³C and HSQC NMR, as well as thermogravimetric analysis (TGA). The results showed that the lignin fractions extracted with microwave heating (20-120 min) had high molecular weights and polydispersities (M_w 3150-5710 g/mol, M_n 2130-3020 g/mol, M_w/M_n 1.48-2.00) as compared to those prepared without microwave heating (M_w 3080 g/mol, M_n 2080 g/mol, M_w/M_n 1.48). The most striking characteristic of all lignin fractions was the almost absence of associated sugars (0.16-3.25%). The TGA results indicated that the thermal stability of the lignin fraction increased with the increment of the molecular weight. FT-IR and NMR spectra suggested that the lignin fractions showed similar structures which were mainly composed of guaiacyl (G) and minor amounts of p-hydroxyphenyl (H) units. Moreover, HSQC NMR spectrum of a typical lignin fraction (prepared with microwave heating for 120 min) revealed that it contained dominant amounts of β-O-4′ linkages (64.6%) and phenylcoumaran (β-5′) substructures (25.8%) together with small amounts of resinol (β-β′) substructures (6.7%) and coniferyl alcohol end groups (2.9%).     

Composition and molecular structure of polysaccharides released from barley endosperm cell walls by sequential extraction with water,malt enzymes,and alkali

Isolated and purified endosperm cell walls (CW), used in this study, were derived from a Canadian malting barley variety, AC Metcalfe, grown in three different environments in Canada in 2003, and varying in grain protein and β-glucan contents, as well as in grain hardness. The CW were initially extracted with water at 45 °C and subsequently digested with barley malt crude enzyme extract resulting in two fractions designated CW-WE45 and CW-MD, respectively. The remaining non-digested cell wall material (CW_ND) was further fractionated by sequential extraction with water at 95 °C (CW_ND-WE95), saturated barium hydroxide (CW_ND-BaE), and 1 N sodium hydroxide (CW_ND-NaE) at 25 °C. Composition and molecular structure analyses were carried out for all fractions including the remaining cell wall residue (CW_RES). Extraction of CW with water followed by digestion with malt crude enzyme extract solubilized the majority of β-glucans (∼55–70%) and glucomannans (∼60–80%) but only a small portion of arabinoxylans (∼20–30%) present in the intact CW. The CW-WE45 and CW_ND-WE95 fractions consisted mostly of β-glucans exhibiting high average molecular weights (M_w) (2–3 × 10⁶), whereas the CW_ND-BaE consisted mainly of arabinoxylans with M_w about 1–1.5 × 10⁶. The CW_ND-NaE contained almost equal amounts of β-glucans and arabinoxylans and a small amount of glucomannans, whereas the CW_RES contained approximately equal proportions of β-glucans, arabinoxylans and glucomannans. β-Glucans in CW_ND-WE95, CW_ND-NaE, and CW_RES exhibited a higher ratio of 3-O-β-d-cellobiosyl-d-glucose to 3-O-β-d-cellotriosyl-d-glucose (DP3/DP4) compared to β-glucans in CW-WE45 and CW-MD. β-Glucans in CW_ND-NaE showed the highest level of long cellulosic oligosaccharides with DP ≥ 5, whereas those in the CW_RES had the highest DP3/DP4 ratio. The CW-MD was fractionated by ultrafiltration into high (CW-MD_HMW) and low-molecular weight (CW-MD_LMW) sub-fractions, with weight-average M_w of ∼150–350 × 10³ and <10 × 10³, respectively, as confirmed by size-exclusion chromatography. The monosaccharide composition of the sub-fractions indicated a more extended enzymic degradation of β-glucans and glucomannans than arabinoxylans. Some differences in composition and molecular structure of the cell wall constituents among the three barley samples were related to their solubility and enzymic digestibility.     

Characterization and degradation of lignin from steam explosion of pine and corn stalk of lignin: The role of superoxide ion and ozone

Steam explosion of corn stalk in the presence of 3% sulphuric acid at 200 °C for 5 min gave the highest recovery of lignin. Lignin has M_w = 2640 and M_z = 93,994. In the UV spectrum absorptions at λ = 231 and 280 nm were recorded. ¹H NMR spectrum of lignin showed signals attributable to cinnamaldehyde units, guaiacyl units, and syringyl units. Syringyl and guaiacyl units are in 1:1 ratio. ¹³C NMR spectrum showed signals for guaiacyl, syringyl, and p-hydroxyphenyl units. The spectrum showed a prevalence of guaiacyl units. The ¹³C NMR spectrum is in agreement with the presence of cinnamic units. The same characterization was performed on lignin from pine. The irradiation of lignin from pine from steam explosion process in the presence of oxygen, in conditions described for the formation of superoxide ion, for different irradiation time was followed isolating the lignin and determining the average molecular weight. The experiments showed that, until 8 h irradiation, M_n decreases, while M_w and M_z increases. After 8 h irradiation an inverse behaviour was observed, with an increase of M_n and a decrease of M_w and M_z. These results are in agreement with an initial polymerization process followed by a photoinduced degradation. Ozonization was carried out in acetonitrile–methanol solution. The reaction showed a zero-order kinetics. After 50 min the average molecular weight of lignin is the half. The reaction mixture was analyzed by using GC–MS. Oxalic acid was determined.     

Water extractable (1→3,1→4)-β-d-glucans from barley and oats: An intervarietal study on their structural features and rheological behaviour

The fine structures and rheological behaviours of aqueous flour dispersions and of β-glucan, (1→3,1→4)-β-d-glucan isolates obtained from 18 registered varieties of normal covered barley seeds and four registered oat varieties, grown in the same location in Greece, were investigated. The β-glucan content of the barleys and oats varied between 2.5–5.4 and 2.1–3.9%, respectively (dry matter basis). Heat treatment of the barley and oat flour dispersions with 80% (v/v) ethanol, to inactivate endogenous β-glucanases, had a stabilizing effect on the viscosity profile of the flour slurries. The relationship between total β-glucan content and aqueous slurry viscosity (at 247 s⁻¹) of the heat-treated barley flours was weak (r²=0.45, p<0.05, n=18). β-Glucans were isolated by water extraction at temperatures slightly below the gelatinization temperature of starch, enzymatic removal of starch and partial removal of contaminating proteins by adjustment to pH 4.0–4.5, and subsequent precipitation of the water-soluble β-glucans with 80% (v/v) ethanol. The cellulosic oligomers released by the action of a (1→3,1→4)-β-d-glucan hydrolase showed cellotriosyl and cellotetraosyl units, accounted for 91.1–92.1% for barley and between 92.4 and 94.1% for the oat preparations; the respective molar ratios of tri- to tetra-saccharides (DP3/DP4) ranged between 2.73–3.05 (barley) and 2.16–2.42 (oat). Steady shear measurements confirmed the random coil type behaviour of freshly prepared β-glucan solutions (5 and 7%, w/v). The rate at which shear thinning began was dependent on both concentration and molecular size of the polysaccharide. Most of the β-glucan dispersions followed the Cox–Merz rule, except Mucio, a variety with high M_w β-glucan (2.39×10⁵). Viscoelastic characterization, at 8% (w/v), of three barley β-glucan aqueous dispersions differing in molecular size, indicated that the low molecular weight sample exhibited shorter gelation time and higher gelation rate (I_E=[dlog G′/dt]_max) than its higher molecular weight counterparts. Small deformation oscillatory measurements on gels of all barley β-glucan isolates (10% (w/v), 7 d storage, 25 °C) revealed a strong negative relationship (r²=0.88, p<0.01) between G′ (1 Hz, strain 0.1%) and apparent M_w of the polysaccharide.     

Foliar application of chitosan activates artemisinin biosynthesis in Artemisia annua L.

There has been much interest in artemisinin owing to its excellent activity against malaria, an infectious disease threatening the tropical world. However, the low artemisinin content (0.01-0.8%, DW) in Artemisia annua, which is the only commercial source of artemisinin, makes artemisinin expensive to produce and not yet available on a global scale. Here we show that foliar application of 100 mg l⁻¹ chitosan improved artemisinin biosynthesis in A. annua. The content of dihydroartemisinic acid and artemisinin in chitosan-treated leaves increased by 72% and 53% compared with control values, respectively. Chitosan induced the expression of ADS and DBR2, which could explain the increase in level of artemisinic metabolites. After chitosan treatment, the amounts of hydrogen peroxide (H₂O₂) and superoxide anion (O₂⁻) in leaves of A. annua were 1.4 and 3.0 times higher than those of the control, respectively. Accumulation of reactive oxygen species (ROS) probably accelerated the conversion of dihydroartemisinic acid to artemisinin. Foliar application of 100 mg l⁻¹ chitosan had no harmful effect on A. annua growth. The simple method described here could be an effective method to improve artemisinin production in A. annua field cultivation.     

Demographic changes in Helicoverpa armigera after exposure to neemazal (1% EC azadirachtin)

We estimated the effect of 5, 10, 15 and 20 mg l⁻¹ of neemazal (1% EC azadirachtin) on life table parameters of Helicoverpa armigera (Hübner) developing on chickpea (Cicer arietinum L.). The effects were assessed on the survivals emerged from 6th instar larvae that had ingested neemazal-treated chickpea pods. Survivorship (I) and expectancy of life (e_x) were highest with the commencement of age (egg) and decreased gradually with the advancement of age with all the concentrations of neemazal including unexposed cohort. All the eggs hatched in the unexposed group while highest numbers of unhatched eggs (10%) were recorded with 20 mg l⁻¹. Mortality of 1st instars was higher at 20 and 15 mg l⁻¹ than that of other concentration tested. Potential fecundity (pf) was reduced in concentration dependent manner and was lowest with 20 mg l⁻¹ (418 eggs/female/generation) and highest in control (898 eggs/female/generation). Net reproductive rate (R₀) was significantly reduced with the increase in concentration of neemazal. The intrinsic (r_m) and finite rate of increase (λ) were significantly decreased at 20 mg l⁻¹ than that of unexposed population. The mean generation time (T_c) was prolonged at 20 mg l⁻¹ and significantly differed with non-treated individuals. Development of immature stages was prolonged to 38 days with 20 mg l⁻¹ while reduced to 32 days with 15 mg l⁻¹ of neemazal as compared to 37 days in untreated individuals. Doubling time (DT) was significantly extended to 5.02 days with 20 mg l⁻¹ as compared to 3.84 days in the non exposed ones.     

Preparation and Characterization of A Semi-interpenetrating Network Alkaline Anion Exchange Membrane

A series of semi-interpenetrating network (semi-IPN) anion exchange membranes (QCS/St-G_8-2-8, Quaternized chitosan/styrene-[maleic alkylene group diethyl bis (octyl dimethyl chloro/bromide), abbreviated as G_8-2-8] were prepared via in-situ polymerization by Styrene (St) and G_8-2-8 in QCS casting solution. During the process of in-situ polymerization, linear block polymers (St-G_8-2-8) of Styrene and G_8-2-8 was constructed, then was mixed with QCS casting solution, followed crosslinking the QCS by glutaraldehyde (GA). With the increasing content of linear block polymer, water uptake and swelling ratio of the composite membrane decreased; This kind of linear structure makes an order arrangement of quaternary ammonium groups which improves the OH? migration efficiency. At 70 °C, the M-30 composite membrane performs a high OH? conductivity of 8.20×10^-2 S·cm^-1, the methanol permeability is 3.23×10^-6 cm^-2·s^-1 which is still lower than Nafion 115 of 2.42×10^-6 cm^-2·s^-1, but M-30 shows a higher selectivity of 25.3 than Nafion 115 of 11.6. Furthermore, the membranes exhibited excellent thermal stability (≥150 °C), the tensile strength of the composite membrane is in the range of 14-25 MPa and elongation at break is in the range of 16-37 % at room temperature, as well as superior chemical stability in 1.0 M KOH solution for 250 h.     

Preparation, structure, and in vitro degradation behavior of the electrospun poly(lactide-co-glycolide) ultrafine fibrous vascular scaffold

The PLGA ultrafine fibrous scaffold was successfully fabricated by electrospinning. The morphology and properties of the PLGA vascular scaffolds were examined. In particular, the in vitro degradation behavior of the electrospun PLGA vascular scaffolds was investigated by means of morphology, microstructure, mass loss, M_w, and breaking strength characterization. The results showed that electrospun scaffold possessed ultrafine fibrous and porous structure, and had adequate mechanical properties to be developed as a substitute for native blood vessels. In vitro degradation study showed that the PLGA ultrafine fibrous scaffold could biodegrade in the PBS solution, and the mass loss, M_w, and breaking strength studies indicated that degradation rate of the electrospun PLGA nanofibers was greater in the first 2 weeks. After the degradation of 2 weeks, the degradation slowed down. Furthermore, with the extension of the degradation time, the thermal decomposition temperature of the PLGA scaffold decreased gradually. The results indicated that the electrospun PLGA vascular scaffold could be considered as an ideal candidate for tissue-engineered blood vessel.     

Supercritical Fluid Extraction of Fucoxanthin from the Diatom Phaeodactylum tricornutum and Biogas Production through Anaerobic Digestion

Phaeodactylum tricornutum is the marine diatom best known for high-value compounds that are useful in aquaculture and food area. In this study, fucoxanthin was first extracted from the diatom using supercritical fluid extraction (SFE) and then using the extracted diatom-like substrate to produce bioenergy through anaerobic digestion (AD) processes. Factors such as temperature (30 °C and 50 °C), pressure (20, 30, and 40 MPa), and ethanol (co-solvent concentration from 10% to 50% v/v) were optimized for improving the yield, purity, and recovery of fucoxanthin extracted using SFE. The highest yield (24.41% w/w) was obtained at 30 MPa, 30 °C, and 30% ethanol but the highest fucoxanthin purity and recovery (85.03mg/g extract and 66.60% w/w, respectively) were obtained at 30 MPa, 30 °C, and 40%ethanol. Furthermore, ethanol as a factor had the most significant effect on the overall process of SFE. Subsequently, P.tricornutum biomass and SFE-extracted diatom were used as substrates for biogas production through AD. The effect of fucoxanthin was studied on the yield of AD, which resulted in 77.15 ± 3.85 LSTP CH₄/kg volatile solids (VS) and 56.66 ± 1.90 LSTP CH₄/kg VS for the whole diatom and the extracted P.tricornutum, respectively. Therefore, P.tricornutuman can be considered a potential source of fucoxanthin and methane and both productions will contribute to the sustainability of the algae-biorefinery processes.     

Effect of neemarin on life table indices of Plutella xylostella (L.)

The effects of neemarin at 5, 10, 15 and 20 mg l⁻¹ on the life table indices of Plutella xylostella (L.) were studied on cauliflower in the laboratory. Survivorship was increased with increasing concentrations. A total of 69% eggs hatched at 20 mg l⁻¹ compared 85% in the control. Mortality (d_x) of 1st instars was higher than the other instars in both exposed and unexposed individuals. Life expectancy (e_x) was high in the untreated control and reduced at 20 mg l⁻¹. Development times of immatures were prolonged to 32 days at 20 mg l⁻¹ as compared to 18.6 days in the untreated control. Neemarin significantly reduced the emergence of adults. Potential fecundity (P_f) was 34 females/female/generation at 20 mg l⁻¹ and 92 in the control. The net reproductive rate (R₀) was significantly reduced with the increase in concentration. The intrinsic rate of increase (r_m) and finite rate of increase (λ) were significantly decreased at 20 mg l⁻¹ as compared to other concentrations tested and in the control. Mean generation time (T_c) and corrected generation time (τ) were prolonged at 20 mg l⁻¹ and significantly differed to those of the untreated control. Doubling time (DT) was significantly extended to 28.4 days at 20 mg l⁻¹ as compared to 6.1 days in the control.     

Starch fine structure and physicochemical properties of specialty rice for canning

The long-grain, specialty rice cultivars, Bolivar, Cheniere, Dixiebelle, and L-205 are used for wet-pack canning. These cultivars have similar apparent amylose content but showed differences in canning, pasting, and gelatinization properties. Starch fine structures were analyzed to rationalize observed differences in functionality. Cheniere amylopectin had the lowest weight-average molar mass (M_w), shortest average chain length (CL), smallest z-average radius of gyration (R_z), lowest proportion of long chains (DP 37–65), and highest polydispersity; while its amylose had the largest M_w and R_z. These structural features were associated with more leached solids in the canning broth, lower volume expansion, lower peak and final viscosity, and lower gelatinization temperature and enthalpy. Bolivar amylopectin had the largest M_w, longest average CL, largest R_z, highest proportion of long chains (DP 25–65), and lowest proportion of short chains (DP 6–12); while its amylose had the smallest M_w and lowest polydispersity. These structures were associated with lower levels of leached solids, higher volume expansion, and higher peak and final viscosity. L-205 was similar to Bolivar in most structural and functional properties; those of Dixiebelle were either comparable to Bolivar or intermediate to Bolivar and Cheniere. These findings point to the importance of the molar mass of amylopectin and the proportion of long and short chains on the canning stability of rice.     

Pre-harvest glyphosate application effects on properties of β-glucan from oat groats

Pre-harvest glyphosate is applied to cereal grains to control weed growth. However, it has been claimed that oat (Avena sativa L.) composition is affected by pre-harvest glyphosate application. The research was conducted to evaluate differences in properties of β-glucan in grains of pre-harvest glyphosate treated versus untreated oat plants. Two oat cultivars (Rockford and Souris) were grown at Minot and Prosper, ND, in 2015, and glyphosate was sprayed during the soft dough stage, hard dough stage, or not applied. β-glucan viscosity was not significantly (p > 0.05) affected by treatment at soft dough (1082 cP) or mature (1166 cP) stages compared with untreated (1150 cP) controls. Applying glyphosate at the soft dough stage significantly (p < 0.05) reduced the content and solubility of the β-glucan versus untreated samples. β-glucan content and solubility in oat treated at soft dough were 4.35% and 52.1%, respectively, while in untreated samples were 4.65% and 60.6%, respectively. Treatment at soft dough and hard dough stages significantly (p < 0.05) increased weight average molecular weight (M_w) of the high molecular weight fraction of soluble β-glucan (4.4 × 10⁶ and 3.8 × 10⁶, respectively), compared with untreated controls (3.5 × 10⁶). The M_w of the low molecular weight fraction of soluble β-glucan fraction significantly (p < 0.05) increased at soft and hard dough treatments (5.5 × 10⁵ and 3.3 × 10⁵, respectively), versus untreated samples (3.0 × 10⁵). Therefore, glyphosate can be applied when the grain has reached physiological maturity or thereafter.     

Rheological and thermal properties of acrylonitrile-acrylamide copolymers: Influence of polymerization temperature

An attempt was made to correlate the polymerization temperature and rheological and thermal properties of acrylonitrile (AN)-acrylamide (AM) copolymers. The copolymers were synthesized at different polymerization temperature. The copolymer structure was characterized by gel permeation chromatography (GPC) and Infrared spectrum (IR). The rheological and thermal properties were investigated by a viscometer and differential scanning calorimeter-thermogrametric (DSCTG) analysis, respectively. When the polymerization temperature increased from 41 °C to 65 °C, the molecular weight ([`(M)] <sub>w</sub> )(\overline M _w ) of copolymers decreased from 1,090,000 to 250,000, while its conversion increased from 18% to 63%, and the polymer composition changed slightly. To meet the requirements of carbon fibers, the rheological and thermal properties of products were also investigated. It was found that the relationship between viscosity and [`(M)] _w\overline M _w was nonlinear and the viscosity index (n) decreased from 3.13 to 2.69, when the solution temperature increased from 30 °C to 65 °C. This suggests the dependence of viscosity upon [`(M)] _w\overline M _w is higher at lower solution temperature. According to the result of activation energy, the sensivity of viscosity to solution temperature is higher for AN-AM copolymers synthesized at higher polymerization temperature. The result of thermal analysis shows that the copolymers obtained at higher polymerization temperature are easier to cyclization evidenced from lower initiation temperature. The weight loss behavior changed irregularly with polymerization temperature due to irregular change of liberation heat.     

Prediction of water quality effect on saturated hydraulic conductivity of soil by artificial neural networks

This study was conducted to investigate the impact of water salinity (EC_w) and sodicity (SAR_w) on saturated (K_s) and relative (K_r) hydraulic conductivities in two clay (C) and sandy clay loam (SCL) soils. The results showed that the K_s decreased with increasing SAR_w, and in all of water quality treatments, the K_s of SCL soil was higher than that of the C soil. Sodicity effect (even at high SAR_w) on the K_r of clay soil was minimized by high salinity. Although K_r of both soils similarly responded to EC_w and SAR_w, microstructure of clay soil was more sensitive to water quality. Effect of EC_w on soil structure was greater than that of SAR_w. In order to assess the applicability of artificial neural networks (ANNs) in estimating K_s and K_r, two types of FFBP and CFBP ANNs and two training algorithms, namely Levenberg–Marquardt (LM) and Bayesian regulation, were employed with two strategies of uniform threshold and different threshold functions. Multiple linear regressions were also used for K_s and K_r prediction. Based on the ANN results of second strategy, best topology (4–5–4–1) was belonged to CFBP network with LM algorithm, LOGSIG–LOGSIG–TANSIG threshold functions, and values of MAE and R² are equal to 0.1761 and 0.9945, respectively. Overall, the efficacy of ANNs is much greater than regression method for K_s prediction.     

Chitosan enhances withanolides production in adventitious root cultures of Withania somnifera (L.) Dunal

Calli were obtained from leaf, cotyledon and internode explants of in vitro-grown plants of Indian cultivar of Withania somnifera in MS medium supplemented with 2, 4-D (2.0 mg l⁻¹) and Kinetin (0.2 mg l⁻¹). The brown, semi-friable callus (500 mg FW) derived from leaf explants produced higher number of primary adventitious roots (9 roots/callus) in half strength MS medium fortified with IBA (0.5 mg l⁻¹) and NAA (0.1 mg l⁻¹). The primary adventitious roots with an inoculum mass of 15 g FW were cultured for 6 weeks in the same medium for secondary adventitious root proliferation. Elicitation of abiotic elicitor, aluminium chloride at 10 mg l⁻¹ at the end of 4 weeks culture with 4 h exposure time enhanced withanolides productivity. Under similar culture conditions, the biotic elicitor, chitosan at 100 mg l⁻¹ stimulated higher production of all withanolides when compared to aluminium chloride treatment. This is the first report on the use of callus-derived adventitious root culture for the enhanced production of withanolides upon chitosan elicitation.     

Amylose and amylopectin in starch by asymmetric flow field-flow fractionation with multi-angle light scattering and refractive index detection (AF4–MALS–RI)

The rheological and functional properties of starch are influenced by the size and molar mass distribution of the polymer, the ratio of amylose (AMY) to amylopectin (AMP), and branching characteristics. Asymmetric Flow Field-Flow Fractionation (AF4) was applied to fractionate five different maize hybrids of varying AMY:AMP ratio. When coupled to detection by multi-angle light scattering and refractive index (MALS–RI), it was possible to determine mass percentage and the average weight-average molar mass (M_w) without the need for calibration standards. Sufficient resolution of amylose and amylopectin was achieved by applying a gradient cross-flow on a 17 cm trapezoidal channel with a 350 μm spacer. The observed M_w ranged from about 2 × 10⁵ to 4 × 10⁵ for amylose and from 1 × 10⁸ to 4 × 10⁸ for amylopectin. The corresponding z-average root-mean-square radii (R_z) for AMP ranged from 145 to over 300 nm. Low recoveries from the AF4 channel were found to be due primarily to the focusing step. The calculated mass percent of AMY and AMP from integrated RI peak areas agreed well with nominal values for the individual starch hybrids. Both qualitative and quantitative data were reproducible. The results show the AF4–MALS–RI method to be well suited for routine molecular characterization of starch.     

Evaluation of Aqueous Biphasic Electrophoresis System Based on Halide-Free Ionic Liquids for Direct Recovery of Keratinase

Aqueous biphasic electrophoresis system (ABES) incorporates electric fields into the biphasic system to separate the target biomolecules from crude feedstock. Ionic liquid (IL) is regarded as an excellent candidate as the phase-forming components for ABES because of the great electrical conductivity, which can promote the electromigration of biomolecules in ABES, and thereby enhances the separation efficiency of the target biomolecules from crude feedstock. The application of electric fields to the conventional biphasic system expedites the phase settling time of the biphasic system, which eases the subsequent scaling-up steps and reduces the overall processing time of the recovery process. Alkyl sulphate-based IL is a green and economical halide-free surfactant when compared to the other halide-containing IL. The feasibility of halide-free IL-based ABES to recover Kytococcus sedentarius TWHK01 keratinase was studied. Optimum partition coefficient (K_e = 7.53 ± 0.35) and yield (Y_T = 80.36% ± 0.71) were recorded with IL-ABES comprised of 15.0% (w/w) [EMIM][ESO₄], 20.0% (w/w) sodium carbonate and 15% (w/w) crude feedstock. Selectivity (S) of 5.75 ± 0.27 was obtained with the IL-ABES operated at operation time of 5 min with 10 V voltage supplied. Halide-free IL is proven to be a potential phase-forming component of IL-ABES for large-scale recovery of keratinase.     

Effects of middle-viscosity chitosan on Ramularia cercosporelloides

The inhibitory properties of middle-viscosity Chitosan on the growth of fungus Ramularia cercosporelloides were studied in vitro. The inhibitory concentration that delayed 50% of the radial growth (IC₅₀) was 3.4 g l⁻¹ for middle-viscosity Chitosans with molecular weights of about 133 and 187 kDa (middle molecular weight) dissolved in lactic and acetic acids, respectively. At 96 h of incubation and under the same growing conditions, inhibitions of 91.79% and 73.13% of the radial growth of the fungus were observed when 3.4 g l⁻¹ of Chitosan was dissolved in 0.05 M acetic and 0.05 M lactic acid, respectively. The biomass production was significantly lower than that observed in the controls at 72 h. Based on these in vitro results; Chitosan could be a good alternative to control the disease caused by R. cercosporelloides on safflower.     

Aflatoxin in maize,a multifaceted answer of Aspergillus flavus governed by weather,host-plant and competitor fungi

Aspergillus section Flavi is able to produce aflatoxins (AFs) in vitro down to 0.85 a_w with a potential maximum occurring between 0.95 and 0.99 a_w, while in the field AFs increased significantly with kernel humidity below 0.95 a_w. In order to clarify this apparent discrepancy, a 3-year field trial with artificial inoculation of maize ears with Aspergillus flavus strains was organised. The co-occurrence of Aspergillus section Flavi and Gibberella fujikuroi species complex (Gfsc) was observed. The incidence of A. flavus was significantly influenced by the year and negatively related to Gfsc incidence. In 2012, when the highest temperature and the lowest rain were registered, aflatoxin B₁ (AFB₁) content was the highest and a_w < 0.95 in kernels was measured early throughout the growing season. In 2013 and 2014, the temperature was lower and rain more abundant, and a_w decreased below 0.95 only close to harvest and AFB₁ contamination was limited. The possibility of describing/predicting reasonably well a_w dynamic based on temperature, (degree day) was confirmed. With a_w > 0.95, a positive correlation between AFB₁ production rate and a_w was found, but a negative correlation resulted with a_w < 0.95. Other factors than a_w play a role, but a_w = 0.95 should be considered as an indicator of suitable conditions for rapid aflatoxin accumulation.