Lipase-coupling esterification of starch with octenyl succinic anhydride

Enzymatic modification of starch was conducted by lipase-coupling esterification with octenyl succinic anhydride (OSA). Parameters affecting the esterification were systematically studied. Products were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, differential scanning calorimetry (DSC) and viscosity analysis (VA). Optimum condition for lipase-coupling OSA starch preparation was as follows: starch pretreatment at 65 °C for 15 min, starch concentration 35%, amount of lipase and OSA, 0.6% and 3%, reaction pH, temperature and time, 8.0, 40 °C and 30 min respectively, which resulted in 0.0195 of the degree of substitution and 84.05 ± 2.07% of the reaction efficiency. FT-IR spectroscopy confirmed the formation of OSA starch. SEM and X-ray diffraction showed apparent surface change, but no crystalline change. DSC and VA results indicated the synthesized OSA starch gelatinized rapidly with high viscosity. Attractively, reaction time drastically reduced to 30 min, showing vast potential for scale production of OSA starch.     

Extraction and chemical characterization of starch from S. lycocarpum fruits

In this study the pulp from Solanum lycocarpum fruits was used as raw material for extraction of starch, resulting in a yield of 51%. The starch granules were heterogeneous in size, presenting a conical appearance, very similar to a high-amylose cassava starch. The elemental analysis (CHNS) revealed 64.33% carbon, 7.16% hydrogen and 0.80% nitrogen. FT-IR spectroscopy showed characteristic peaks of polysaccharides and NMR analysis confirmed the presence of the α-anomer of d-glucose. The S. lycocarpum starch was characterized by high value of intrinsic viscosity (3515 mPa s) and estimated molecular weight around 645.69 kDa. Furthermore, this starch was classified as a B-type and high amylose content starch, presenting 34.66% of amylose and 38% crystallinity. Endothermic transition temperatures (T_o = 61.25 °C, T_p = 64.5 °C, T_c = 67.5 °C), gelatinization temperature (ΔT = 6.3 °C) ranges and enthalpy changes (ΔH = 13.21 J g⁻¹) were accessed by DCS analysis. These results make the S. lycocarpum fruit a very promising source of starch for biotechnological applications.     

Preparation of crystalline starch nanoparticles using cold acid hydrolysis and ultrasonication

Waxy maize starch in an aqueous sulfuric acid solution (3.16 M, 14.7% solids) was hydrolyzed for 2–6 days, either isothermally at 40 °C or 4 °C, or at cycled temperatures of 4 and 40 °C (1 day each). The starch hydrolyzates were recovered as precipitates after centrifuging the dispersion (10,000 rpm, 10 min). The yield of starch hydrolyzates depended on the hydrolysis temperature and time, which varied from 6.8% to 78%. The starch hydrolyzed at 40 °C or 4/40 °C exhibited increased crystallinity determined by X-ray diffraction analysis, but melted in broader temperature range (from 60 °C to 110 °C). However, the starch hydrolyzed at 4 °C displayed the crystallinity and melting endotherm similar to those of native starch. The starch hydrolyzates recovered by centrifugation were re-dispersed in water (15% solids), and the dispersion was treated by an ultrasonic treatment (60% amplitude, 3 min). The ultrasonication effectively fragmented the starch hydrolyzates to nanoparticles. The hydrolyzates obtained after 6 days of hydrolysis were more resistant to the ultrasonication than those after 2 or 4 days, regardless of hydrolysis temperatures. The starch nanoparticles could be prepared with high yield (78%) and crystallinity by 4 °C hydrolysis for 6 days followed by ultrasonication. Scanning electron microscopy revealed that the starch nanoparticles had globular shapes with diameters ranging from 50 to 90 nm.     

The single source preparation of rod-like mercury sulfide nanostructures via hydrothermal method

High-quality and high-yield rod-like HgS dendrites with cubic structure was synthesized by a wet chemical route, without using any surfactant and organic solvents at 180 °C for 5 h, by using Hg(NO₃)₂·H₂O and thioglycolic acid (TGA) as starting reagents. The obtained HgS with different morphologies and sized were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). The effects of reaction parameters, such as temperature, precursor concentration and reaction time on the morphology and particle size of products were investigated. Our experimental results showed that temperature reaction played key role in the final morphology of HgS. The morphology of HgS nanostructures could be changed from rod-like dendrites to nanoparticles by only decreased temperature reaction to 110 °C. In the present study the possible mechanism of HgS nanoparticles growth to dendrites in the aqueous solution was also discussed and the optical properties rod-like HgS dendrites were investigated by ultraviolet-visible (UV-Vis) spectroscopy.     

Pyrolytic characteristics of biomass acid hydrolysis residue rich in lignin

Pyrolytic characteristics of acid hydrolysis residue (AHR) of corncob and pinewood (CAHR, WAHR) were investigated using a thermo-gravimetric analyzer (TGA) and a self-designed pyrolysis apparatus. Gasification reactivity of CAHR char was then examined using TGA and X-ray diffractometer. Result of TGA showed that thermal degradation curves of AHR descended smoothly along with temperature increasing from 150 °C to 850 °C, while a “sharp mass loss stage” for original biomass feedstock (OBF) was observed. Char yield from AHR (42.64-30.35 wt.%) was found to be much greater than that from OBF (26.4-19.15 wt.%). In addition, gasification reactivity of CAHR char was lower than that of corncob char, and there was big difference in micro-crystallite structure. It was also found that CAHR char reactivity decreased with pyrolysis temperature, but increased with pyrolysis heating rate and gasification temperature at 850-950 °C. Furthermore, CAHR char reactivity performed better under steam atmosphere than under CO₂ atmosphere.     

Effect of temperature on gelatinization and retrogradation in high hydrostatic pressure treatment of potato starch-water mixtures

The effect of temperature (20-70 °C) on the gelatinization and retrogradation of potato starch-water mixtures (10-70%, w/w) treated with high hydrostatic pressure (HHP) (400-1000 MPa) was investigated. Gelatinization enthalpy change (ΔH_gel) and re-gelatinization enthalpy change of retrograded crystalline part (ΔH_retro) of the HHP-treated starch were evaluated using differential scanning calorimetry. The value of ΔH_gel of 10-20% (w/w) mixtures decreased with increased pressure and temperature, while ΔH_gel of 30-50% (w/w) mixtures decreased to certain values with increased pressure and the values depended on treatment temperature. With higher temperature and pressure conditions, ΔH_gel of 10-40% (w/w) mixtures reached zero, but ΔH_gel of 50-70% (w/w) mixtures did not. Retrogradation was observed with HHP-treated 20-60% (w/w) mixtures and the value of ΔH_retro depended on the starch content, pressure, and temperature. The value of ΔH_retro trended to increase with increase in starch content. In addition, retrogradation was promoted by HHP treatment at low temperature. Gelatinizaiton and retrogradation behaviors of HHP-treated (400-1000 MPa) potato starch-water mixtures (10-70%, w/w) at 20-70 °C were summerized in a series of state diagrams.     

Influence of native starch's properties on starch nanocrystals thermal properties

Starch nanocrystals (SNC) are crystalline square-like platelet about 10 nm thick and 50-100 nm equivalent diameters. Depending on the botanic origin of starch these platelets show different features. The aim of the present study was (i) to assess the thermal stability of SNC in different processing conditions (i.e., excess water and dry) and (ii) to investigate the potential influence of botanic origin on thermal stability. The thermal properties of five types of starches (waxy maize, normal maize, high amylose maize, potato and wheat) and their corresponding SNC were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SNC revealed two endothermic transitions. No correlation between melting temperature and botanic origin was found. However, a review of starch thermal properties allowed to postulate for the mechanism involved in SNC thermal transitions. It was also found that SNC can be used in wet processes below 100 °C and in dry processes below 150-200 °C to avoid melting.     

Effects of acclimation temperature on thermal tolerance, locomotion performance and respiratory metabolism in Acheta domesticus L. (Orthoptera: Gryllidae)

The effects of acclimation temperature on insect thermal performance curves are generally poorly understood but significant for understanding responses to future climate variation and the evolution of these reaction norms. Here, in Acheta domesticus, we examine the physiological effects of 7-9 days acclimation to temperatures 4 °C above and below optimum growth temperature of 29 °C (i.e. 25, 29, 33 °C) for traits of resistance to thermal extremes, temperature-dependence of locomotion performance (jumping distance and running speed) and temperature-dependence of respiratory metabolism. We also examine the effects of acclimation on mitochondrial cytochrome c oxidase (CCO) enzyme activity. Chill coma recovery time (CRRT) was significantly reduced from 38 to 13 min with acclimation at 33-25 °C, respectively. Heat knockdown resistance was less responsive than CCRT to acclimation, with no significant effects of acclimation detected for heat knockdown times (25 °C: 18.25, 29 °C: 18.07, 33 °C: 25.5 min). Thermal optima for running speed were higher (39.4-40.6 °C) than those for jumping performance (25.6-30.9 °C). Acclimation temperature affected jumping distance but not running speed (general linear model, p = 0.0075) although maximum performance (U_MAX) and optimum temperature (T_OPT) of the performance curves showed small or insignificant effects of acclimation temperature. However, these effects were sensitive to the method of analysis since analyses of T_OPT, U_MAX and the temperature breadth (T_BR) derived from non-linear curve-fitting approaches produced high inter-individual variation within acclimation groups and reduced variation between acclimation groups. Standard metabolic rate (SMR) was positively related to body mass and test temperature. Acclimation temperature significantly influenced the slope of the SMR-temperature reaction norms, whereas no variation in the intercept was found. The CCO enzyme activity remained unaffected by thermal acclimation. Finally, high temperature acclimation resulted in significant increases in mortality (60-70% at 33 °C vs. 20-30% at 25 and 29 °C). These results suggest that although A. domesticus may be able to cope with low temperature extremes to some degree through phenotypic plasticity, population declines with warmer mean temperatures of only a few degrees are likely owing to the limited plasticity of their performance curves.     

Insights in starch acetylation in sub- and supercritical CO2

An in-depth study on the acetylation of starch with acetic anhydride (Ac₂O) and sodium acetate (NaOAc) as the catalyst in pressurized carbon dioxide (scCO₂) in a broad pressure range (8–25 MPa) and a temperature of 90 °C is provided. Highest degrees of substitution (DS) of 0.29 (1 h reaction time) and 0.62 (24 h reaction time) were found near the critical point of the mixture (15 MPa). The phase behavior of the system CO₂, starch and acetic anhydride (Ac₂O) was studied in a high pressure view cell. The critical points were a clear function of the temperature and increased from the range of 9.4–10 MPa to 14.5–14.8 MPa when going from 50 to 90 °C (Ac₂O mole fraction at the critical point in the range of 0.08–0.09). Acetylation experiments with a range of starch particles sizes showed a clear relation between the DS and the particle size.     

Definition and characterization of enzymes for maximal biocatalytic solubilization of prebiotic polysaccharides from potato pulp

Potato pulp is a high-volume co-processing product resulting from industrial potato starch manufacturing. Potato pulp is particularly rich in pectin, notably galactan branched rhamnogalacturonan I polysaccharides, which are highly bifidogenic when solubilized. The objective of the present study was to characterize and compare four homogalacturonan degrading enzymes capable of catalyzing the required solubilization of these pectinaceous polysaccharides from potato pulp in a 1 min reaction. An additional purpose was to assess the influence of the pH and the potential buffer chelating effects on the release of these polysaccharides from the potato pulp. The pH and temperature optima of two selected pectin lyases from Emericella nidulans (formerly known as Aspergillus nidulans) and Aspergillus niger were determined to 8.6 and 4.0, respectively, at ≥100 °C within 1 min of reaction. The optima for the two selected polygalacturonases from E. nidulans and Aspergillus aculeatus were determined to pH 4.4 and 46 °C, and pH 3.7 and ≥80 °C, respectively. The polygalacturonase from A. aculeatus was 4-42 times more heat-resistant at 50 °C than the other enzymes. The difference in pH optima of the pectin lyases and the exceptional thermal stabilities of some of the enzymes are proposed to be related to specific amino acid substitutions, stabilizing hydrogen bonding and structural traits of the enzymes. The K_M and V_max values ranged from 0.3-0.6 g/L and 0.5-250.5 U/mg protein, respectively. Phosphate buffer induced release of a higher amount of dry matter than Tris-acetate buffer at pH 6, indicating a chelating effect of the phosphate. Moreover, the phosphate had a higher chelating effect at pH 6 than at pH 4. The optimal conditions for a high yield of polysaccharides from potato pulp were therefore: 1% (w/w) potato pulp treated with 1% (w/w) enzyme/substrate (E/S) pectin lyase from E. nidulans and 1% (w/w) E/S polygalacturonase from A. aculeatus at pH 6.0 and 60 °C for 1 min.     

Optimization of conditions for production of sago starch-based foam

Production of sago starch-based foam involved mixing of sago starch with polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) followed by preparation of electron beam irradiated sago starch/PVA and sago starch/PVP sheets and expanding them in a microwave. The results revealed that good foams with high linear expansion and closed cell structure can be produced from 25:15 of sago starch:PVA and 30:10 of sago starch:PVA blends prepared at 80 °C and electron beam irradiated at 15 kGy or 10 kGy for the cross-linking process. An increment of sago starch in the blends enhanced the linear expansion of the foams produced. Change in the blend morphology was observed when it was exposed to higher irradiation doses as electron beam irradiation induced the cross-linking in PVA and PVP, and leaching of amylose and amylopectin from the starch granules. Sago starch/PVA blend is more suitable for foam production because it produced flexible and glossy foam as compared to sago starch/PVP blend which produced very rigid foam.     

Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil

The new type of catalyst for fatty acid methyl esters (FAME or biodiesel) synthesis with K₂CO₃ as active component on alumina/silica support was synthesized using sol–gel method. Corresponding catalyst (xerogel) was prepared by 12 h drying the wet gel in air at 300 °C, 600 °C or 1000 °C at atmospheric pressure. The catalysts activity in the methanolysis of sunflower oil was compared to the activity of the pure K₂CO₃. The effects of various reaction variables on the yield of FAME were investigated. It was found that the temperature of 120 °C and methanol to oil molar ratio of 15:1, are optimal conditions for FAME synthesis with synthesized catalyst. Repeated use of same amount of catalyst indicated that effect of potassium leaching obviously existed leading to decrease of catalyst activity.     

Engineering the thermostability of a TIM-barrel enzyme by rational family shuffling

A possible approach to generate enzymes with an engineered temperature optimum is to create chimeras of homologous enzymes with different temperature optima. We tested this approach using two family-10 xylanases from Thermotoga maritima: the thermophilic xylanase A catalytic domain (TmxAcat, T_opt = 68 °C), and the hyperthermophilic xylanase B (TmxB, T_opt = 102 °C). Twenty-one different chimeric constructs were created by mimicking family shuffling in a rational manner. The measured temperature optima of the 16 enzymatically active chimeras do not monotonically increase with the percentage of residues coming from TmxB. Only four chimeras had a higher temperature optimum than TmxAcat, the most stable variant (T_opt = 80 °C) being the one in which both terminal segments came from TmxB. Further analysis suggests that the interaction between the N- and C-terminal segments has a disproportionately high contribution to the overall thermostability. The results may be generalizable to other enzymes where the N- and C-termini are in contact.     

The use of small subcutaneous transponders for quantifying thermal biology and torpor in small mammals

Remote measurements of body temperature (T_b) in animals require implantation of relatively large temperature-sensitive radio-transmitters or data loggers, whereas rectal temperature (T_rec) measurements require handling and therefore may bias the results. We investigated whether ∼0.1 g temperature-sensitive subcutaneously implanted transponders can be reliably used to quantify thermal biology and torpor use in small mammals. We examined (i) the precision of transponder readings as a function of temperature and (ii) whether subcutaneous transponders can be used to remotely record subcutaneous temperature (T_sub). Five adult male dunnarts (Sminthopsis macroura, body mass 24 g) were implanted with subcutaneous transponders to determine T_sub as a function of time and ambient temperature (T_a), and in comparison to thermocouple readings of T_rec. Transponder temperature was highly correlated with water bath temperature (r²=0.96–0.99) over a range of approximately 10.0–40.0 °C. Transponders provided reliable data (±0.6 °C) over the T_sub of 21.4–36.9 °C and could be read from a distance of up to 5 cm. Below 21.4 °C, accuracy was reduced to ±2.8 °C, but individual transponder accuracy varied. Consequently, small subcutaneous transponders are useful to remotely quantify thermal physiology and torpor patterns without having to disturb the animal and disrupt torpor. Even at T_sub<21.4 °C where the accuracy of the temperature readings was reduced, transponders do provide reliable data on whether and when torpor is used.     

Germanium tetra(tertiary butoxide): Synthesis, structure and its utility as a precursor for the preparation of europium doped germanium oxide nanoparticles

Germanium tetra(tertiary butoxide), [Ge(O^tBu)₄], has been prepared by the reaction of GeCl₄ with KOBu^t in benzene. It is a monomeric crystalline solid having a distorted tetrahedral configuration, defined by the coordination of four OBu^t groups around germanium atom. The TG analysis showed that the compound is thermally stable and volatilizes at around 130 °C. Europium doped and un-doped germanium oxide nanoparticles were prepared based on the urea hydrolysis of Ge(O^tBu)₄/Eu(OOCCH₃)₃ in ethylene glycol medium at 150 °C followed by heating the resulting product at 750 °C. The nanoparticles were characterized by XRD, TEM and PL measurements. The europium doped nanoparticles, which were nearly monodispersed (∼30 nm), showed luminescence and the Eu³⁺ ions were occupying the surface of the GeO₂ nanoparticles.     

Pasting viscosity and in vitro digestibility of retrograded waxy and normal corn starch powders

Pasting viscosity and in vitro digestibility of oven-dried powders of waxy and normal corn starch gels (40% solids) retrograded under an isothermal (4 °C) or temperature cycled (4/30 °C) storage were investigated. Temperature cycling induced higher onset temperature for melting of amylopectin crystals than isothermal storage under a differential scanning calorimeter whereas little difference in crystalline type was observed under X-ray diffraction analysis. Temperature cycling caused higher pasting temperature and viscosity for the retrograded starches than isothermal storage. The retrograded waxy corn starch powders exhibited pasting behaviors similar to that of native waxy corn starch. However, the retrograded normal corn starch powders showed very much different pasting patterns with lower pasting viscosity but higher pasting temperature than native starch counterpart. The retrogradation increased slowly digestible starch content without changing resistant starch content, more effectively by the temperature cycling than the isothermal storage.     

Multi-objective optimization of bioethanol production during cold enzyme starch hydrolysis in very high gravity cassava mash

Cold enzymatic hydrolysis conditions for bioethanol production were optimized using multi-objective optimization. Response surface methodology was used to optimize the effects of α-amylase, glucoamylase, liquefaction temperature and liquefaction time on S. cerevisiae biomass, ethanol concentration and starch utilization ratio. The optimum hydrolysis conditions were: 224 IU/g_starch α-amylase, 694 IU/g_starch glucoamylase, 77 °C and 104 min for biomass; 264 IU/g_starch α-amylase, 392 IU/g_starch glucoamylase, 60 °C and 85 min for ethanol concentration; 214 IU/g_starch α-amylase, 398 IU/g_starch glucoamylase, 79 °C and 117 min for starch utilization ratio. The hydrolysis conditions were subsequently evaluated by multi-objectives optimization utilizing the weighted coefficient methods. The Pareto solutions for biomass (3.655-4.380 × 10⁸ cells/ml), ethanol concentration (15.96-18.25 wt.%) and starch utilization ratio (92.50-94.64%) were obtained. The optimized conditions were shown to be feasible and reliable through verification tests. This kind of multi-objective optimization is of potential importance in industrial bioethanol production.     

Improved cold starch hydrolysis with urea addition and heat treatment at subgelatinization temperature

We explore how the presence of urea can influence the kinetics of amylolysis, with a long-term objective of developing practical and energy efficient bioconversion protocols. In this study, triticale and corn starches were hydrolyzed by a granular starch hydrolyzing enzyme with or without addition of urea and a pre-heating treatment at subgelatinization temperature. Differential scanning calorimetry showed that the gelatinization parameters of triticale and corn starches were negatively correlated with the urea concentration in the starch suspension. Addition of urea did not significantly affect starch amylolysis by the granular starch hydrolyzing enzyme at 30 °C. However when pre-heating at a higher yet sub-gelatinization temperature (50 °C for triticale and 61 °C for corn, 5 °C below the onset of starch gelatinization) for 30 min, the presence of urea greatly facilitated the amylolysis of both tricticale and corn starches. Scanning electron microcopy revealed starch granule mophological changes to a porous structure in residual starch granules/fragments rich in resistant starch. This means that the amylolysis pattern in the presence of urea was fundamentally changed, and urea disrupts starch hydrogen bonds effectively with heating treatment at a sub-gelatinization temperature. This treatment combination increased both starch hydrolysis rate and extent. Since extra energy was not necessary to gelatinize starch, this method may benefit starch and bio-enthanol industries to reduce the costs of starch hydrolysis.     

Study on the heterogeneous degradation of chitosan with H2O2 catalyzed by a new supermolecular assembly crystal: [C6H8N2]6H3[PW12O40]·2H2O

A new supermolecular assembly crystal, [C₆H₈N₂]₆H₃[PW₁₂O₄₀]·2H₂O (DMB-PWA), was synthesized with phosphotungstic acid (PWA) and 1,2-diaminobenzene (DMB) under hydrothermal conditions and was characterized by Fourier-transform infrared spectra (FTIR) and single-crystal X-ray diffraction analysis. DMB-PWA could effectively catalyze oxidative degradation of chitosan with H₂O₂ in the heterogeneous phase. The optimum degradation conditions were determined by orthogonal tests as follows: amount of chitosan 1.00 g, 30% (wt %); H₂O₂, 3.0 mL; dosage of catalyst, 0.06 g; reaction temperature, 85 °C; and reaction time, 30 min. The water-soluble chitosan with a viscosity-average molecular weight (M_v) of 4900 was obtained under the optimum degradation conditions and was characterized by FTIR, ultraviolet-visible diffuse reflection spectra (UV-vis DRS), and X-ray powder diffraction analysis.     

Interaction of Na2B12H11SH with dimyristoyl phosphatidylcholine liposomes

Previous investigations have revealed that the boron cluster compound Na₂B₁₂H₁₁SH (BSH) is very potent in causing major structural rearrangements of and leakage from phosphatidylcholine liposomes. This somewhat unexpected finding is interesting from a fundamental point of view and may also constitute the basis of future important pharmaceutical/medical applications of BSH. In order to further explore the BSH-lipid interaction, we have studied the effects caused by BSH on dimyristoyl phosphatidylcholine (DMPC) liposomes.Cryo-transmission electron microscopy showed that BSH induces aggregation, membrane rupture and increasing wall thickness of the liposomes. Differential scanning calorimetry revealed a BSH dependent shift of the gel to liquid crystalline phase transition temperature of DMPC. The zeta potential of the liposomes decreases with increasing BSH concentrations, and an apparent dissociation constant of 0.23 mM was found.BSH caused leakage of liposome-encapsulated carboxyfluorescein; leakage was higher at 23 °C (near the phase transition temperature) than at 15 °C and 37 °C. It induced lipid mixing only at very high concentrations.