Low Glycerol Concentrations Research Articles

Chickpea flour‐based biofilms containing gallic acid to be used as active edible films

ABSTRACTChickpea is an easily accessible nutritious legume. Besides, gallic acid is a widespread phenolic found in various plants. In this study, it is aimed to investigate the effects of pH (9 and 11), glycerol concentration (1 and 3% w/v of film solution) and gallic acid concentration (5 and 10% w/w of total solid) on color, opacity, mechanical strength, water vapor permeability (WVP), microstructure, chemical characteristic, antioxidant activity, and phenolic content of films. At pH 11, films are stronger, darker and have higher antioxidant activity. Higher glycerol concentration makes the films more flexible but less strong and more hydrophilic. Higher gallic acid concentration makes great contribution to the films by decreasing WVP but by increasing opacity, antioxidant activity, phenolic content, lightness, and elongation. Film containing glycerol of 1% and gallic acid of 10% and prepared at pH 11 was found to be a great combination for obtaining antioxidant rich edible composite films.HIGHLIGHTS Chickpea flour‐based active films were successfully obtained with addition of gallic acid. Higher gallic acid concentration decreased WVP, increased opacity, antioxidant activity, phenolic content, lightness, and elongation. Higher pH provided stronger mechanical properties, low lightness, and higher antioxidant activity. Lower glycerol concentration resulted lower WVP and stronger tensile properties. Chickpea flour‐based active films at pH 11 with 1% glycerol and 10% gallic acid can be used as active packaging material in especially highly oxidative food products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47704.

Effects of Carbon Nanotube and Carbon Sphere Templates in TiO2 Composites for Photocatalytic Hydrogen Production

Incorporation of carbonaceous templates (CT) into TiO2 composites is a promising alternative to increase the photocatalytic activity of TiO2. In this work, the effects of carbon sphere (CS) and carbon nanotube (CNT) incorporation (as CT) in TiO2 composites were thoroughly investigated and the roles of these CTs as template, cocatalyst, and adsorbent were studied. To this end, three different methods were utilized to form a layer of TiO2 on the CT: alcoholic phase sol–gel, aqueous phase sol–gel, and hydrothermal. The role of CT as template was examined through morphology analysis of the prepared composites. The cocatalyst and adsorbent roles of CT were investigated based on photocatalytic hydrogen production from glycerol. Interestingly, it was found that the incorporation of CNT into TiO2 composite can approximately double the rate of hydrogen production (i) in the absence of Pt or (ii) at low glycerol concentration. Accordingly, it was concluded that in addition to being a template, the CNT can play two ...

Laying hen manure in anaerobic Co-Digestion with glycerin containing different glycerol and impurity levels

Biodiesel has arisen as a promising option of renewable fuel to minimize the impacts caused by fossil fuels. However, its production process generates high amounts of crude glycerin as a residue, which is considered low-quality commercially due to its low glycerol content. In order to add value to this byproduct, some production plants employ a purification process. Nonetheless, aiming to cut down costs with this purification step, many researches have been seeking treatments that use glycerin with lower purity, such as anaerobic co-digestion with another residue of complementary composition so as to balance the digestion medium and increase energy yield. During recycling, glycerin goes from an environmental liability to a sustainable financial asset by being transformed into cleaner energy, i.e., biogas. This research was carried out to assess the influence of glycerol content in glycerin containing the same impurities at three proportions (40% (G40), 60% (G60), and 80% (G80)), and to add them to the process at different glycerol levels (0, 1, 2, 3, and 4%) in the total solids (TS) of the affluents prepared with laying hen manure. No interaction was found between glycerin type and glycerol content regarding biogas and methane productions as well as reductions in TS and volatile solids (VS). Adding 2.5% glycerol led to the highest specific biogas production (1654.1 L kg−1 VS added) while adding 2.6% yielded the maximum specific production of methane (1058.9 L kg−1 VS added), i.e., glycerol increased methane generation by over 36% when compared with the treatment with no glycerin. Consequently, greater reductions in TS (60.97%) and VS (73.6%) were observed with ideal addition levels of 2.2 and 2.4% glycerol. Adding 2.1% glycerol using G40 resulted in the greatest reduction (55.4%) in chemical oxygen demand (COD) whereas such reduction was by 50.4 and 50.5% for G60 and G80 when 2.6% glycerol were added. With that in mind, and in face of the high costs of purification, G40 can be recommended with addition of 2.6% glycerol to TS to improve co-digestion with laying hen manure and generate energy that returns to poultry and biodiesel production systems.

Influence of yeasts of the genus Saccharomyces and not Saccharomyces in elaboration of white wines

Traditionally the Serra Gaúcha region, in the state of Rio Grande do Sul, is known as a barn productor of excellent quality wines. The aromatic complexity of wine in general, and white wine in particular, is what is essential to satisfy an increasingly demanding consumer. Among the most used techniques to achieve this purpose is the addition of yeasts of different genres, thus providing a range of aromatic characteristics that are accentuated in it. In this sense, the objective of this work was to evaluate the use of different strains of yeasts in white wines of Riesling Italic variety, made from grapes grown in the Serra Gaúcha region, in the state of Rio Grande do Sul. Based on the results, it was possible to observe that there were no significant differences between the treatments in relation to the variables pH, total acidity and alcoholic degree. However, with respect to the fermentation yield, T3 was the treatment that obtained the best performance, reaching the ideal density (below 1000 g.cm3) in the course of 6 to 7 days, followed by treatments T1 (Saccharomyces cerevisae) and T5 (Levulia pulcherrima) (7 to 8 days), with treatments T2 (Saccharomyces cerevisaecerevisae) and T4 (Torulaspora delbrueckii), which had the lowest performance (9 to 10 days). The T4 treatment was also the one that presented a higher amount of residual sugars, which proves the less activity of this yeast in more alcoholic means. All the yeasts used have a low production of volatile acidity, but the lowest concentration was Saccharomyces cerevisae cerevisae, used in treatment T2 (0.1 gL−1), and the other treatments presented higher concentrations (0, 4 to 0.5 gL−1), although it is still within the parameters considered ideal for obtaining quality white wines. T2 was also the treatment with lower concentrations of glycerol (5.1 g.L−1). This compound is mainly formed by glyceropyruvic fermentation through the metabolism of yeasts at the beginning of alcoholic fermentation, usually being produced by the first 50 grams of fermented sugars, which may indicate a greater activity of this yeast in this fermentation period. In general, we can say that all the yeasts used have the potential to produce quality white wines, since they had good fermentation yields, satisfactory production of alcohol and glycerol, and low production of volatile acidity.

Effects of combined pullulan polysaccharide, glycerol, and trehalose on the mechanical properties and the solubility of casted gelatin-soluble edible membranes

Protein-biodegradable edible membranes are environmentally friendly and economical to the food packaging industry compared with traditional packaging materials. In the present study, the mechanical properties (including flexibility index, viscosity index, brittleness index and texture comprehensive index) and solubility of casted gelatin-soluble edible membranes were investigated as functions of the contents of pullulan polysaccharide (0.0%, 0.5%, 2.5%, 5.0%, 7.5%), glycerol (0.0%, 0.5%, 2.5%, 5.0%, 7.5%), and trehalose (0.0%, 0.5%, 2.5%, 5.0%, 7.5%). The results indicated that the texture comprehensive index of the membrane increased from 4.65 ± 0.22 to 5.85 ± 0.10, while solubility decreased from 10 to 9.0 ± 0.20 as the pullulan polysaccharide’s concentration increased (0%–2.5%), that it had an adverse effect on solubility. For the membrane with glycerol, the texture comprehensive index increased at a low glycerol concentration range (0%–2.5%), while decreased at a high concentration rage (2.5%–7.5%). Trehalose had similar effect to glycerol on the texture comprehensive index and a similar effect to pullulan polysaccharide on solubility. The resultant membranes with better flexibility, less brittleness, and greater solubility could be used to pack instant coffee, noodles, milk powder, and other food in food applications. Practical applications With the intensification of a series of pollution problems caused by plastic products and people's attention to food safety, various countries are striving to find a "green packaging material." In many "green packaging," the edible film attracts much attention. Are natural edible substances (such as polysaccharides, proteins, and lipids) as raw materials, added edible plasticizers, crosslinking agents, etc., through different molecular interactions, and wrapped, coated, micro-capsules and other forms cover the surface or inside of foods to block the penetration of moisture, oxygen, or various solutes to protect them. The current study is mostly a single base film with gelatin as the main body, and there are significant differences in their properties. For example, the protein film has poor water resistance, but the gas barrier property is relatively strong. The water resistance of the large polysaccharide film is not good, but there are some outstanding advantages. For example, its heat sealability and water solubility are better. Gelatin, glycerol, pullulan, and trehalose are compounded to make edible films. Their mechanical properties and water solubility are good. They are suitable for packing instant coffee, instant noodles, instant milk powder, and other food materials.

Direct Evidence for the Effect of Glycerol on Protein Hydration and Thermal Structural Transition

The mechanisms of protein stabilization by uncharged solutes, such as polyols and sugars, have been intensively studied with respect to the chemical thermodynamics of molecular crowding. In particular, many experimental and theoretical studies have been conducted to explain the mechanism of the protective action on protein structures by glycerol through the relationship between hydration and glycerol solvation on protein surfaces. We used wide-angle x-ray scattering (WAXS), small-angle neutron scattering, and theoretical scattering function simulation to quantitatively characterize the hydration and/or solvation shell of myoglobin in aqueous solutions of up to 75% v/v glycerol. At glycerol concentrations below ∼40% v/v, the preservation of the hydration shell was dominant, which was reasonably explained by the preferential exclusion of glycerol from the protein surface (preferential hydration). In contrast, at concentrations above 50% v/v, the partial penetration or replacement of glycerol into or with hydration-shell water (neutral solvation by glycerol) was gradually promoted. WAXS results quantitatively demonstrated the neutral solvation, in which the replacement of hydrated water by glycerol was proportional to the volume fraction of glycerol in the solvent multiplied by an exchange rate (β ≤ 1). These phenomena were confirmed by small-angle neutron scattering measurements. The observed WAXS data covered the entire hierarchical structure of myoglobin, ranging from tertiary to secondary structures. We separately analyzed the effect of glycerol on the thermal stability of myoglobin at each hierarchical structural level. The thermal transition midpoint temperature at each hierarchical structural level was raised depending on the glycerol concentration, with enhanced transition cooperativeness between different hierarchical structural levels. The onset temperature of the helix-to-cross β-sheet transition (the initial process of amyloid formation) was evidently elevated. However, oligomerization connected to fibril formation was suppressed, even at a low glycerol concentration.

The Effect of Pre- and Post-injection Procedural Factors on Blastocyst Rate After ICSI

Cryopreservation of epididymal sperm allows the saving of genetic material in case of unexpected death or emergency castration. The aim of the present study was the comparison of five different combinations of extenders commercially available for equine frozen semen processing for cryopreservation of epididymal sperm. Epididymal sperm were harvested from gonads of 10 healthy stallions after routine castration by retrograde flush technique. Then, samples were split and diluted with (1) INRA96 + INRA Freeze, (2) BotuSemen + BotuCRIO, (3) EquiPlus + Gent Freeze, (4) EquiPlus + EquiPlus Freeze, and (5) Gent + Gent Freeze. Extenders 1 and 2 showed higher values for total and progressive motility after thawing compared with extender 4 (P < .05). Extender 3 was in between 1 and 2 (P > .05), and extender 5 resulted in the lowest values (P < .05). The subpopulation of viable frozen-thawed sperm with high mitochondrial membrane potential and low intracellular calcium content was higher using extender 1 compared with extenders 3, 4, and 5 (P < .05) and higher in extender 2 compared with extenders 4 and 5 immediately after thawing (P < .05). After 1 hour of incubation, this subpopulation yielded the highest values in extender 2 (P < .05). Immediately after thawing, extender 1 yielded higher values for percentage of DFI and mean DFI than extenders 3, 4, and 5 (P < .05). Following 1 hour of incubation after thawing, sperm processed with extender 1 resulted in the highest values for percentage of DFI and mean DFI (P < .05). Using extender 2, mean DFI values were lower than those in extender 1 and higher than the extenders 3, 4, and 5 (P < .05). The study revealed that according to the examined sperm quality parameters, freezing extenders (extender 1, extender 2) using low concentrations of glycerol either combined with or without methylformamide were beneficial for cryopreservation of stallion epididymal sperm. For processing of stallion epididymal sperm, an extender containing milk proteins (extenders 1–4) for initial dilution after sperm harvesting is preferable to an extender including egg yolk (extender 5).

The Effect of Helium on Cryopreservation of HeLa and L929 Cells

The effect of helium on cell survival during cryopreservation was studied using the HeLa and L929 cell lines. Cell suspensions were incubated in an atmosphere of helium, nitrogen, or air and frozen in the presence or absence of glycerol as a cryoprotectant. After thawing, the cell viability was evaluated by the Trypan Blue exclusion test and culture development for 18 h. Helium was found to provide better preservation of cell suspensions compared with nitrogen and air. The positive effect of helium was the greatest in the case of freezing without cryoprotectants (the HeLa cell survival increased by a factor of 1.5–2) and somewhat lower in the case of freezing in the presence of low glycerol concentrations (the L929 cell survival increased by a factor of 1.2–1.5 in the presence of 3% glycerol). Use of helium for cell suspensions may improve cryopreservation methods by making it possible to reduce the concentrations of conventional cryoprotectants, which are generally highly toxic and undesirable to use for cryopreservation of biological material for medical applications.

Effects of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) microparticles on morphological, mechanical, thermal, and barrier properties in thermoplastic potato starch films

Biocomposites of potato starch/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microparticles were prepared through the solvent casting method. Glycerol was used as a plasticizer. The effects of concentrations of PHBV microparticles as filler and glycerol on crystallinity behavior, surface morphology, dynamic mechanical properties, and thermal stability were studied. Humidity absorption and the water vapor transmission rate (WVTR) were investigated as well. Wide angle X-ray scattering (WAXS) patterns revealed that the plasticizing process occurred successfully. Scanning electron microscopy (SEM) micrographs exhibited good homogeneity of the surfaces for the biocomposites with a lower glycerol concentration. Dynamic mechanical analysis (DMA) results confirmed the reinforcing effect of PHBV microparticles inside the matrix. Thermogravimetric analysis (TGA) indicated that the presence of PHBV microparticles increased the thermal stability of the starch. Results of humidity absorption tests showed that the high hydrophilicity of the starch was reduced once the PHBV microparticles had been incorporated. Also, increasing PHBV microparticles reduced the water vapor transmission rate. However, samples with reduced glycerol content absorbed less humidity and showed a lower water vapor transmission rate.

Molecular Packing, Hydrogen Bonding, and Fast Dynamics in Lysozyme/Trehalose/Glycerol and Trehalose/Glycerol Glasses at Low Hydration.

Water and glycerol are well-known to facilitate the structural relaxation of amorphous protein matrices. However, several studies evidenced that they may also limit fast (∼picosecond-nanosecond, ps-ns) and small-amplitude (∼Å) motions of proteins, which govern their stability in freeze-dried sugar mixtures. To determine how they interact with proteins and sugars in glassy matrices and, thereby, modulate their fast dynamics, we performed molecular dynamics (MD) simulations of lysozyme/trehalose/glycerol (LTG) and trehalose/glycerol (TG) mixtures at low glycerol and water concentrations. Upon addition of glycerol and/or water, the glass transition temperature, Tg, of LTG and TG mixtures decreases, the molecular packing of glasses is improved, and the mean-square displacements (MSDs) of lysozyme and trehalose either decrease or increase, depending on the time scale and on the temperature considered. A detailed analysis of the hydrogen bonds (HBs) formed between species reveals that water and glycerol may antiplasticize the fast dynamics of lysozyme and trehalose by increasing the total number and/or the strength of the HBs they form in glassy matrices.

Development and characterization of a novel edible extruded sheet based on different casein sources and influence of the glycerol concentration

Different source of casein depending on their extraction method from milk are available on the market. Sheets from 3 different types of casein (rennet casein, acid casein and sodium caseinate) were developed using a dry process: extrusion. Casein sourcing, plasticizer concentration (13.2% w/w or 24.2% w/w) and relative humidity environment were studied for each sheet through color, density and porosity, water sensitivity and mechanical properties evaluation. A wide range of properties seems to be available through casein based sheets depending on casein source, which affected greatly water solubility (caseinates are 100% water soluble compare to acid and rennet casein). Besides, acid and rennet casein have different behaviour with water and even more with higher glycerol amounts. Indeed, rennet casein sheet is less sensitive to water than acid casein sheet at low glycerol concentration (13.2% w/w) but at the opposite, at high glycerol amount in sheets, rennet casein sheet is more hydrophilic than acid casein sheets.Extrusion is an easy scale up process and it was used to produce casein based sheets with improved water vapor permeability (WVP). These findings can be used to find the suitable food packaging application for each casein based sheet with a low cost and efficient process.

THE EFFECT OF GLYCEROL CONTENT ON MECHANICAL PROPERTIES, SURFACE MORPHOLOGY AND WATER ABSORPTION OF THERMOPLASTIC FILMS FROM TACCA LEONTOPETALOIDES STARCH

Tacca leontopetaloides is a new plant source of starch and has high potential to produce film of thermoplastic. In this study, thermoplastic starch (TPS) derived from T.leontopetaloides was developed with glycerol as plasticizer through casting method at temperature range from 85 °C to 90 °C and enhanced with sulphur vulcanization method. It was found that the addition of 5%, 10%, 15%, 20% and 25% (v/v) of glycerol into T.leontopetaloides starch had affected the mechanical properties, surface morphology, and water absorption of the thermoplastic films. In the mechanical properties study, the TPS films have the highest tensile strength (47.96 MPa) at 5% glycerol content in the formulation. Conversely, the TPS films have increasing value of elongation at break (EAB) with increasing glycerol concentration with the higher EAB obtained at 25% glycerol content (52.90%). The morphology of thermoplastic film was examined by using Scanning Electron Microscopy (SEM). As glycerol content increased, thermoplastic films showed smoother surface, homogenous and good distribution. In water absorption test, TPS films showed lower affinity to water absorption at lower glycerol content. The weight of the TPS films increased ranging from 80.3% to 107.4% after 12 hour of immersion in water. It can be concluded that, glycerol significantly affected the properties of TPS film within the range of glycerol concentration studied.

Influence of glycerol and an alternative humectant on the immediate and 3-hours bactericidal efficacies of two isopropanol-based antiseptics in laboratory experiments in vivo according to EN 12791

BackgroundGuidelines for hand hygiene recommend the use of alcohol-based hand rubs containing humectants in order to improve dermal tolerance. However, the bactericidal efficacy of pre-surgical hand rubs is negatively affected by the WHO-recommended humectant glycerol, especially the 3-h efficacy. The aim of this study was to investigate whether replacing glycerol as humectant increases the bactericidal efficacy of surgical hand rubs based on isopropanol (75%, wt/wt).Material and methodsThe efficacy of 3 and 5 min applications of a modified WHO II-formulation (containing lower glycerol concentrations) and the TPH 5766 hand rub which contains a new humectant (containing ethylhexylglycerin, dexpanthenol and a fatty alcohol) were compared to the European Norm 12,791 reference (n-propanol, 60%, vol/vol) immediately following and 3 h after application.ResultsImmediately after application both isopropanol-based surgical rubs approximated the performance of the reference. The 3-h effect of the modified WHO II-formulation was found to be less efficacious than the EN 12791, showing a 30% decrease in log10 reduction values. The 3-h post application effect for the TPH 5766 hand rub was found to not be different from EN 12791.ConclusionBased on our data, the bactericidal efficacy of isopropanol-based surgical hand rubs can best be obtained if glycerol is not used in the formulation. Unlike glycerol, a humectant comprised of ethylhexylglycerin, dexpanthenol and a fatty alcohol was found not to decrease hand rub effectiveness. Further investigation of the bactericidal efficacy of other humectants is necessary and may prove useful.

Plasticizing Effects of Polyamines in Protein-Based Films

Zeta potential and nanoparticle size were determined on film forming solutions of native and heat-denatured proteins of bitter vetch as a function of pH and of different concentrations of the polyamines spermidine and spermine, both in the absence and presence of the plasticizer glycerol. Our results showed that both polyamines decreased the negative zeta potential of all samples under pH 8.0 as a consequence of their ionic interaction with proteins. At the same time, they enhanced the dimension of nanoparticles under pH 8.0 as a result of macromolecular aggregations. By using native protein solutions, handleable films were obtained only from samples containing either a minimum of 33 mM glycerol or 4 mM spermidine, or both compounds together at lower glycerol concentrations. However, 2 mM spermidine was sufficient to obtain handleable film by using heat-treated samples without glycerol. Conversely, brittle materials were obtained by spermine alone, thus indicating that only spermidine was able to act as an ionic plasticizer. Lastly, both polyamines, mainly spermine, were found able to act as “glycerol-like” plasticizers at concentrations higher than 5 mM under experimental conditions at which their amino groups are undissociated. Our findings open new perspectives in obtaining protein-based films by using aliphatic polycations as components.

EVALUATION OF BIOCONVERSION CONDITIONS ON REUTERIN PRODUCTION USING RESPONSE SURFACE METHODOLOGY AND LISTERIA MONOCYTOGENES AS TARGET BACTERIA

The objective of this study was to evaluate the effect of bioconversion conditions on reuterin production by Lactobacillus reuteri using response surface methodology (RSM). A central composite design consisted of three independent factors at 5 levels: concentration of Lactococcus reuteri (log CFU/ml), glycerol concentration (mM), and incubation time (h) was set up and consisted of 18 experimental runs. The dependant factor was the relative reuterin concentration expressed through its antibacterial activity (Units reuterin per ml, U/ml) against L. monocytogenes using microbroth dilution assay. A polynomial equation for prediction of reuterin production (U/ml) produced by L. reuteri was created based on obtained data. Results showed that incubation time, bacterial and glycerol concentrations had linear positive effects on reuterin production. The quadratic effect of incubation time had negative effect on reuterin production in which at a fixed bacterial concentration of L. reuteri, a longer incubation time with low concentration of glycerol will cause the reduction in relative reuterin concentration. It was found that approximately 450 U/ml can be produced by L. reuteri with glycerol concentration ranging from 320 to 340 mM mM, L. reuteri concentration of 9.4 log CFU/ml and 2 h of incubation. Results demonstrated that applying suitable conditions for glycerol bioconversion into reuterin by L. reuteri, a high relative reuterin concentration could be obtained and used for food preservation against L. monocytogenes.

Direct transesterification of Botryococcus sp. catalysed by immobilized lipase: Ultrasound treatment can reduce reaction time with high yield of methyl ester

Methyl esters have been considered a promising alternative fuel for fossil fuels. However, the methyl ester production from lipase catalysed direct transesterification is a time-consuming process. It is necessary to develop the method to reduce the operating time of the lipase catalysed direct transesterification. Various operating parameters were studied such as solvent/algae ratio, catalyst addition, water addition, temperature and reaction time on the direct transesterification of Botryococcus sp. with and without ultrasound. The maximum yield, 88% methyl esters (w/w of oil) was achieved in 4h with ultrasound treatment under optimum conditions, compared to a maximum yield of 78% methyl esters (w/w of oil), after 36h without ultrasound. Under optimum conditions, the transesterification of Botryococcus sp. oil with dimethyl carbonate produced 2.7% glycerol carbonate and 5.7% glycerol dicarbonate (w/w of oil) with an added benefit of very low free glycerol content. The properties of methyl esters obtained were found to be within the acceptable limits. The obtained results indicate that this ultrasound assisted direct transesterification of Botryococcus sp. oil catalysed by lipase is very promising for biodiesel production using microalgae as the feedstock.

Pyrolysis and combustion kinetics of glycerol-in-diesel hybrid fuel using thermogravimetric analysis

Thermal and oxidative behavior of glycerol-in-diesel hybrid (GDH) fuel systems with different contents of glycerol and their corresponding pyrolysis and combustion kinetics were studied. The thermogravimetric (TG) analysis indicates that different fuel systems had similar TG curves, which means their thermal and oxidative degradation similarities. The different compositions of the fuel systems or the addition of surfactant rhamnolipid and glycerol by forming microemulsion fuel with proper amount of glycerol and forming emulsion with excess glycerol, led diesel to an increasing degradation temperature and decomposition rate without exception. However, the kinetic performance of these fuel systems was different. Although GDH fuel with different contents of glycerol had comparable average activation energies, GDH fuel with high glycerol content (the emulsion fuel) had significantly higher activation energies at high conversion rate in air atmosphere than that of microemulsion fuel (with low glycerol content). Emulsion GDH fuel may have long ignition delay and can possibly result in incomplete combustion and further lead to heavier pollutant emissions when it is used in engines. GDH fuel should be produced with proper amount of glycerol addition in order to achieve better engine performances and emission characteristics.

Effects of Protein Concentration, Plasticiser, and pH on the Properties of Protein Films from Whitemouth Croaker (Micropogonias furnieri) Residues

ABSTRACTProteins have been used extensively because of their relative abundance, nutritional qualities, and film-forming ability with a good structural integrity and mechanical properties. This study investigated the effects of protein isolate and glycerol concentration and pH on the properties of protein films obtained from Whitemouth croaker (Micropogonias furnieri) residues. The films were evaluated for mechanical properties, thickness, water solubility, water vapor permeability (WVP), and morphological properties. The lowest water solubility of the films occurred at low pHs and low glycerol concentrations. The films had high elongation and higher tensile strength when prepared with higher concentrations of protein isolate, lower concentrations of glycerol, and at lower pHs. The WVP and thickness of the films had a low correlation coefficient. The films were rough and had irregular surfaces. These results indicated that protein isolates from fish of low commercial value can be used as a component of new polymeric films for packaging. However, more studies are needed to assess their barrier action against oxygen, thermal behaviors, and their performance in different types of packaging.

Bitter vetch (Vicia ervilia) seed protein concentrate as possible source for production of bilayered films and biodegradable containers

The manufacture of biodegradable and renewable containers from bitter vetch seed protein-based “bioplastics” was investigated. A bitter vetch seed protein concentrate was prepared and analyzed for proteins, carbohydrates, phenols, other several organic compounds and multi-elements. Protein film forming solutions were cast in the presence of two different glycerol concentrations and the film containing higher plasticizer amount was laminated with an additional corn zein layer. Both lamination process and lower glycerol concentration led to reduce film moisture content, total soluble matter and elongation at break, while both film tensile strength and water vapour barrier properties resulted enhanced. The obtained bioplastics were then processed by a new laboratory plastic moulding equipment specifically designed and fabricated to convert protein-based films to shaped containers. The use of either lower plasticizer concentration or corn zein lamination gave rise to potentially satisfactory vacuum thermoformed containers with acceptable resistance and stability.

A biorefinery approach to microbial oil production from glycerol by Rhodotorula glutinis

The use of biodiesel-derived glycerol as a carbon source for microbial oil production is a biorefinery engineering strategy that aims to reduce the glycerol surplus and make the microbial oil process more cost-effective. In this work, glycerol was used as the sole carbon source for the cultivation of the oleaginous yeast Rhodotorula glutinis along with only yeast extract as a nutrient supply and without pH control. Shake-flask cultivations showed that the specific growth rate and glycerol consumption of Rhodotorula glutinis were higher at lower glycerol concentrations (≤40 g L−1), while higher C/N atom ratios enhanced oil content. The present study extends the knowledge on the influence of the aeration rate and oxygen supply in cellular growth rate and microbial oil production, providing a wiser use of glycerol as an attempt to further reduce process costs. Cultivations at different air flow rates were performed in a 2 L bioreactor and showed that a low aeration rate of 0.5 L min−1 gave the best glycerol and nitrogen uptake rates, resulting in the highest growth (5.3 g L−1) and oil mass fraction (33% of the dry cell weight). A further 68% increase in cellular growth (16.8 g L−1) and a 34% oil mass fraction of the dry cell weight was achieved after applying a feeding strategy targeting combined growth and oil production.