Influence Of Glycerol Concentration Research Articles

Use of a Plasticizer for Physical Stability Prediction of Amorphous Solid Dispersions

Utilizing glycerol as a plasticizer, an accelerated physical stability testing method of amorphous solid dispersions (ASDs) was developed. The influence of glycerol concentration on the glass transition temperature and α-relaxation time (a measure of molecular mobility) of amorphous ketoconazole, celecoxib, and the solid dispersions of each prepared with polyvinylpyrrolidone was investigated. By temperature scaling (Tg/T), the effects of glycerol concentration and temperature on the relaxation time were simultaneously evaluated. Glycerol, in a concentration dependent manner, accelerated crystallization in all of the systems without affecting the fragility. In celecoxib-PVP ASDs, the drug crystallization was well coupled to molecular mobility and was essentially unaltered at glycerol concentrations up to 2% w/w. The acceleration in crystallization brought about by glycerol expedited the determination of the coupling between molecular mobility and crystallization. As a result, we were able to predict the ph...

Influence of glycerol concentration on survival of entomopathogenic nematodes through cryopreservation

A modified procedure based on reduced concentration of glycerol for cryopreservation of infective juvenile stage nematodes has been developed using indigenous isolates Steinernema and Heterorhabditis collected from Vietnam. The survival of infective juveniles (IJs) depended on some factors such as concentration of glycerol, IJs concentration and timing for thawing. Optimum survival for both genera was archived with 12,000 IJs/ml in glycerol and 7,500 IJs/ml in ringer’s solution. For Steinernema strains optimum survival also was observed with 12,000 IJs/ml in 10% glycerol concentration whereas with the same IJs concentration in 7.5% Glycerol concentration. The maximum retentions of Steinernem were 45.9-95% whereas these retentions of Heterorhabditis isolates were 81.5-95.2%. The survival of Vietnamese epn isolates in post-cryopreservation was more or less low that only 4 Steinernema isolates among 26 treated were survival whereas only 3 per 12 Heterorhabditis isolates were post-cryopreservation survival. Among survival isolates, apart from two isolates S-TG10 and S-TX1 with survival percentage was lower as 5 and 45.9%, respectively, remaining isolates with survival percentage was higher as 70-95%. For toxicology, Steinernema were 78-87 retention of original virulence to GM larvae, whereas this toxicology of Heterorhabditis was 76-83.5 retention of original virulence to GM larvae.

Influence of Glycerol and Temperature on the Rheological Properties of Potato Starch Solutions

Abstract Effects of temperature and glycerol concentration on rheological properties of potato starch solutions were investigated. The flow behaviour (shear stress against shear rate) was fitted to various models: power law, Herschel-Bulkley, Bingham, modified Bingham and Casson models. However, it was found that the Herschel-Bulkley model describes better the flow behaviour observed at various temperatures and glycerol concentrations, for flow behaviour index values between 0.44 and 0.78, typical of pseudoplastic solutions. The effect of glycerol concentration on each of the fitting parameters for Herschel-Bulkley model was well modelled by a second-degree polynomial at various temperatures. The simultaneous influence of glycerol concentration and temperature on shear stress could be represented empirically by a second-degree polynomial function that includes linear coupling between concentration and temperature. Finally, the variation of the consistency coefficient with both temperature and glycerol concentration was well described by an exponential expression, with an activation energy value of 2.78 kJ mol-1. The results indicate that both glycerol content and temperature have the effect of diluting potato starch solutions.

Conversion of residual glycerol from biodiesel synthesis into 1,3-propanediol by a new strain of Klebsiella pneumoniae

A stepwise strategy was devised to optimize the bioconversion of residual glycerol from biodiesel synthesis into 1,3-propanediol (1,3-PD) by a new strain Klebsiella pneumoniae. This strain is unique in its ability to convert glycerol simultaneously into 1,3-PD. The influence of glycerol concentration, pH, temperature, nitrogen and mineral sources were first investigated using the Plackett–Burman (P–B) statistical design to screen the variables that significantly affect the production of 1,3-PD. Seven variables were statistically significant at 95% significance and a 27-3 fractional factorial design (FFD) was applied to further refine the optimization of culture conditions. Results showed that the ideal medium composition and culture conditions for the syntheses of 1,3-PD are: glycerol 65 g/L, yeast extract 5 g/L, peptone 5 g/L, (NH4)2SO4 7 g/L, K2HPO4 7 g/L, and temperature of 37 °C. Experiments in batch bioreactors under controlled pH produced up to 23.80 g/L of 1,3-PD and 12.30 g/L of ethanol, while in fed-batch cultivations a three-fold increase of 1,3-PD production (36.86 g/L) was obtained compared with the results of the FFD design.

Biotechnological Utilization of Biodiesel-Derived Glycerol for the Production of Ribonucleotides and Microbial Biomass

Ten yeast strains were evaluated concerning their capabilities to assimilate biodiesel-derived glycerol in batch cultivation. The influence of glycerol concentration, temperature, pH and yeast extract concentration on biomass production was studied for the yeast selected. Further, the effect of agitation on glycerol utilization by the yeast Hansenula anomala was also studied. The yeast H. anomala CCT 2648 showed the highest biomass yield (0.30 g g(-1)) and productivity (0.19 g L(-1) h(-1)). Citric acid, succinic acid, acetic acid and ethanol were found as the main metabolites produced. The increase of yeast extract concentration from 1 to 3 g L(-1) resulted in high biomass production. The highest biomass concentration (21 g L(-1)), yield (0.45 g g(-1)) and productivity (0.31 g L(-1) h(-1)), as well as ribonucleotide production (13.13 mg g(-1)), were observed at 700 rpm and 0.5 vvm. These results demonstrated that glycerol from biodiesel production process showed to be a feasible substrate for producing biomass and ribonucleotides by yeast species.

Development and optimization of biodegradable films based on achira flour

Abstract The influence of glycerol concentration ( C g ), process temperature ( T p ), drying temperature ( T s ), and relative humidity (RH) on the properties of achira flour films was initially assessed. The optimized process conditions were C g of 17 g glycerol/100 g flour, T p of 90 °C, T s of 44.8 °C, and RH of 36.4%. The films produced under these conditions displayed high mechanical strength (7.0 MPa), low solubility (38.3%), and satisfactory elongation values (14.6%). This study showed that achira flour is a promising source for the development of biodegradable films with good mechanical properties, low water vapor permeability, and solubility compared to films based on other tubers.

Hydrogenolysis of Glycerol to Propanediols Over Highly Active Ru–Re Bimetallic Catalysts

Several supported Ru–Re bimetallic catalysts (Ru–Re/SiO2, Ru–Re/ZrO2, Ru–Re/TiO2, Ru–Re/H-β, Ru–Re/H–ZSM5) and Ru monometallic catalysts (Ru/SiO2, Ru/ZrO2, Ru/TiO2, Ru/H-β, Ru/H–ZSM5) were prepared and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160 °C, 8.0 MPa and 8 h. Compared with Ru monometallic catalysts, the Ru–Re bimetallic catalysts showed much higher activity in the hydrogenolysis of glycerol, and Re exhibited obvious promoting effect on the performance of the catalysts. The supported Ru monometallic catalysts and Ru–Re bimetallic catalysts were characterized by N2 adsorption/desorption, XRD, TEM-EDX, H2-TPR and CO chemisorption for obtaining some physicochemical properties of the catalysts, such as specific surface areas, crystal phases, morphologies/microstructure, reduction behaviors and dispersion of Ru metal. The results of XRD and CO chemisorption indicate that the addition of Re component could improve the dispersion of Ru species on supports. The measurements of H2-TPR revealed that the coexistence of Re and Ru components on supports changed the respective reduction behavior of Re or Ru alone on the supports, indicating the existence of synergistic effect between Ru and Re species on the bimetallic catalysts. The hydrogenolysis of some products (such as 1,2-propanediol, 1,3-propanediol, 1-propanol and 2-propanol) were also examined over Ru and Ru–Re catalysts for evaluating influence of Re–Re on the reaction routes during glycerol hydrogenolysis. The results showed that over Ru–Re catalysts, glycerol was favorable to be converted to 1,2-propanediol, but not favorable to ethylene glycol, while 1,2-propanediol and 1,3-propanediol were favorable to be converted to 1-propanol. The influence of glycerol concentration in its aqueous solution on the catalytic performance was also evaluated over Ru and Ru–Re catalysts.

Influence of the glycerol concentration on some physical properties of feather keratin films

The influence of glycerol concentration on some physical properties such as the thermal, mechanical, water solubility, hydrophilicity and water barrier properties of feather keratin films was studied. Feather keratin was extracted with an aqueous solution of urea, 2-mercaptoethanol and sodium dodecyl sulphate (SDS) at 50°C and pH 9.0. Film-forming solutions were prepared with 7 g keratin/100 ml, adding glycerol at level concentrations of 0.01, 0.03, 0.05, 0.07 and 0.09 g glycerol/g keratin. The films tensile strength decreased from 16.6±5.5 to 2.0±0.2 MPa and the elongation at break increased from 1.7±0.7% to 31.9±4.5%, while the water vapor permeability of keratin films increased from 5.19×10 −8 to about 10 −6 g m/m 2 h Pa for samples without plasticizer and prepared with 0.09 g glycerol/g keratin, respectively. Films solubility was also increased from 0.307 to 0.507 g/g of initial dry matter when 0.09 g glycerol/g keratin was added. The use of the hydrophilicity concept was very useful to understand the phenomena controlling the water vapor barrier offered by the film, and can be useful as a procedure to investigate this phenomenon in other situations.

Influence of glycerol concentration and carbopol molecular weight on swelling and drug release characteristics of metoclopramide hydrogels

The formulation of glycerol-crosslinked Carbopol 907 and Carbopol 941 metoclopramide hydrogels for buccal administration were investigated. Infrared spectroscopy showed that crosslinking was the result of ester formation between Carbopol carboxyl groups and glycerol hydroxyl groups. The effects of Carbopol molecular weight and glycerol concentration on swelling and drug release characteristics were evaluated. In all glycerol-containing formulations drug dissolution efficiencies were low, and both dissolution efficiency and swelling rate decreased with increasing glycerol concentration, confirming the very high crosslinking capacity of glycerol.

Influence of Glycerol Concentration and Freezing Rate on Post-thaw Motility of Bovine Spermatozoa in Continental Straws

Semen from each of six bulls was used to study the effects of percent glycerol and rate of freezing on spermatozoa extended in egg yolk-sodium citrate extender and packaged in .25-ml Continental1 straws. Treatments were arranged factorially and included 5, 6, 7, 8, 9, 10, or 11% (volume/volume) glycerol; freezing rates (time from 5 to —130C) of 1, 2, 3.5, 7, 12, or 20min; and post-thaw incubation times of 0 and 2h at 38C. Post-thaw motility was similar for spermatozoa frozen in 2 to 20min, and all means were greater than for spermatozoa frozen in 1min. Post-thaw motility of spermatozoa frozen in 7% glycerol did not differ from that with 5 to 9% but was superior to that with 10 or 11% glycerol. Although glycerol and freezing rate interacted, 7% glycerol provided survival equal to or greater than that with the other percents of glycerol, regardless of freezing rate.