Spray-dried encapsulation of chia essential oil (Salvia hispanica L.) in whey protein concentrate-polysaccharide matrices

Eight chia essential oil-in-water fresh emulsions (E) variations were prepared using biopolymers blends whey protein concentrate (WPC) with mesquite gum (MG) or gum Arabic (GA), core to wall material ratios (C_o:W_a) of 1:2 and 1:3, and total solids contents (TSC) of 30 and 40 wt%. All E variations displayed volume-weighted mean size (d_4,3) droplet sizes that fell within 2.32 and 3.35 μm and rates of droplet coalescence (k_C) of 10⁻⁸ s⁻¹. E variations were spray-dried and the resulting microcapsules (M) had d_4,3 falling within the range of 13.17–28.20 μm. The encapsulation efficiency (EE) was higher than 70% for all M, but those obtained from E with lower TSC and higher C_o:W_a displayed higher EE and lower surface oil, independently of M particle size. The reconstituted emulsions (RE) exhibited significantly higher d_4,3 and k_C values of the same magnitude as E variations.     

Development of a Higee bioreactor (HBR) for production of polyhydroxyalkanoate: Hydrodynamics,gas–liquid mass transfer and fermentation studies

This study addresses the hydrodynamics and mass transfer characterisation of a Higee bioreactor (HBR) for application to polyhydroxyalkanoate (PHA) production from Pseudomonas putida KT2442 fermentation. The motivation for this work is to address the potential oxygen transfer limitations which can severely impede the progress of this aerobic fermentation process and reduce PHA productivity in conventional bioreactors. It is shown that a maximum of 2.5 transfer units can be achieved in an oxygen-stripping operation where the presence of packing, higher rotor speeds, higher air flowrates and lower liquid flowrates all have a positive influence on the number of transfer units (NTU). We also observed from a visualisation study that gas bubbles as small as 0.36 mm in diameter can be generated within the HBR operating at 1200 rpm. Preliminary results from the P. putida fermentation studies in the HBR indicate that biomass concentrations of up to 0.5 g/l can be achieved with a maximum PHA yield of 6.2%, both of which are lower than those achieved in a conventional stirred tank reactor. The reasons for the relatively poor performance of the HBR in the context of the fermentation study are discussed and suggestions for improvement are presented.     

Poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate copolymers for pH responsive and shape memory hydrogel

Multifunctional hydrogels combining the capabilities of cellular pH responsiveness and shape memory, are highly promising for the realization of smart membrane filters, controlled drug released devices, and functional tissue‐engineering scaffolds. In this study, lipase was used to catalyze the synthesis of medium‐chain‐length poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate (PHA‐PEGMA) macromer, which was used to prepare pH‐responsive and shape memory hydrogel via free radical polymerization. Increasing the PEGMA fraction from 10 to 50% (mass) resulted in increased thermal degradation temperature (T_d) from 430 to 470°C. Highest lower critical solution temperature of 37°C was obtained in hydrogel with 50% PEGMA fraction. The change in PEGMA fraction was also found to highly influence the hydrogel's hydration rate (r) from 2.8 × 10^?5 to 7.6 × 10^?5 mL·s^?1. The hydrogel's equilibrium weight swelling ratio (q_e), protein release and its diffusion coefficient (D_m) were all found to be pH dependent. Increasing the phosphate buffer pH from 2.4 to 13 resulted in increased q_e from 2 to 16 corresponding to the enlarging of network pore size (ξ) from 150 to 586 nm. Different types of crosslinker for the hydrogel influenced its flexibility and ductility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41149.     

Influence of chitosan derivatization on its physicochemical characteristics and its use as enzyme support

Chitosan was derivatized by two methodologies for analyzing their effect on chitosan physicochemical characteristics and its applicability as carrier for Bacillus circulans β‐galactosidase immobilization. Glutaraldehyde (GA) and epichlorohydrin (EPI) were used for crosslinking and activation of chitosan, producing the corresponding supports (C‐GA and C‐EPI‐EPI) after a one‐step and a two‐step process, respectively. The spherical shape and mean diameter of chitosan particles was not significantly affected by polymer derivatization, while Fourier transform infrared analysis showed that in both cases, chitosan polymer was chemically modified. TGA analysis indicated that C‐EPI‐EPI was the most thermally stable. The high degree of activation of C‐EPI‐EPI (586 μmol of aldehydes/g) resulted in the highest loss of activity during immobilization; hence a support with 100 μmol of aldehydes/g was produced (C‐EPI‐EPI₁₀₀). The highest expressed activity (89.3 IU/g) was obtained with the enzyme immobilized in C‐GA, while the biocatalyst with highest thermal stability at 60°C was obtained with C‐EPI‐EPI₁₀₀ (half‐life was 84‐fold higher than the one of the soluble enzyme). The best compromise between biocatalyst expressed activity and thermal stability corresponded to β‐galactosidase immobilized in C‐EPI‐EPI₁₀₀. According to this study, chitosan derivatized with EPI is a thermally stable carrier appropriate for producing highly stable immobilized B. circulans β‐galactosidase. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40171.     

The kinetics of poly(butylene succinate) synthesis and the influence of molar mass on its thermal properties

The synthesis of poly(butylene succinate) (PBS) of M_w ranging from 4000 to 180,000 g mol^?1 is realized with molar ratios [COOH]₀/[OH]₀ of 1 and 0.98, and varying amounts of titanium (IV) tetrabutoxide (TBT) catalyst. Polycondensation kinetics are followed by chemical titration of carboxylic groups, and the kinetic rate constants of self‐catalyzed and external‐catalyzed reactions are calculated. The synthesis of PBS with high molar mass follows the classical Flory theory. The effect of molar mass on PBS thermal properties is also studied. A faster crystallization rate and a higher temperature of crystallization are observed, for very high molar masses. This behavior could be due to a memory effect of the polymer. Complex melting behavior of PBS is induced by a continuous reorganization of the crystalline phase, as observed by MTDSC. DSC measurements also reveal that the crystallinity—and so the amorphous phase—is limited to about 35% when the molar mass M_n is higher than 40,000 g mol^?1. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40639.     

Electrically conductive bioplastics based on chitosan,polyvinyl alcohol,polyvinyl pyrrolidone,and plant extract nanoparticles for detecting Rhizopus stolonifer on tomato fruit

This work aimed to manufacture bioplastics with mechanical and electrical properties for monitoring the Rhizopus stolonifer growth in tomato fruit packaging. Bioplastics were based on chitosan/polyvinyl alcohol (Ch/PVA), chitosan/polyvinyl pyrrolidone (Ch/PVP), and nanoparticles (NPs) of plant extracts at 10% and 30% of concentrations. Bioplastics were exposed to tomato inoculated with R. stolonifer for 6 d at 25°C. Water vapor permeability (WVP), mechanical properties, FTIR, UV–vis, morphology, electrical resistance of bioplastics, and the NPs size were assessed. In bioplastics added with plant extracts, 1.5 times more WVP than in the control group (18–35 gs⁻¹m⁻¹Pa⁻¹) were quantified. Ch/PVA bioplastic showed 51% more tensile strength, 44% more elongation at break, and 40% more Young's modulus than Ch/PVP, regardless of the plant extract. The electrical resistance in Ch/PVA bioplastics with 30% mushroom extract and 10% radish allowed the differentiation between inoculated (10⁹–10¹⁰ Ω) and non-inoculated tomatoes (10¹⁰–10¹¹ Ω). The FTIR assay confirmed the presence of each compound used in the bioplastic, and UV–vis confirmed phenols at 300 nm. The NPs measured less than 50 nm. Only Ch/PVA with 30% mushroom and 10% radish can be useful to monitor fungi in tomatoes based on their electrical behavior.     

Biodegradable geotextiles – An overview of existing and potential materials

Geotextiles are a group of mostly thermoplastic polymers, which are processed to flexible material sheets, and are installed on various landscapes for reinforcing or protective purposes. Most applied materials in the field are non-degradable polymers, such as polyolefins or polyesters, which can implicate environmental problems concerning soil pollution and accumulation of micro plastics. Because of these drawbacks, for some applications time-consuming re-collection of the material becomes necessary. Hence, the development of more environmentally friendly and biodegradable geotextiles is of interest for several application purposes. In this review biodegradable alternatives to the conventional polymeric geotextile fibers are discussed. In general, there are two material classes available, which are natural fibers and biodegradable polymers. While there is already quite a number of natural-fiber-based geotextiles available on the market, the idea of applying industrial biopolymers for this purpose is relatively unexplored. Geotextile fabrics, made of plant fibers, represent a promising approach and were already successfully installed in several applications. However, the use of natural fibers also entails some limitations regarding water uptake and stability. Therefore, the potential use of a different material class, which comprises degradable, thermoplastic biopolymers, is discussed in this overview as well. There is only little information available on the use of these biopolymers in connection with geotextiles, thus their suitability regarding biodegradation, price and mechanical properties were evaluated.     

The effect of biopolymer dispersants on copper flotation in the presence of kaolinite

In this study, three lignosulfonate-based biopolymers, DP1775, DP1777 and DP1778 with different compositions were examined as dispersants in copper flotation in the presence of kaolinite. While rheological measurements indicated that these biopolymers dispersed the kaolinite aggregates, flotation results revealed that the three biopolymers increased the copper recovery, with a decline in copper grade, which was attributed to an interaction of biopolymers with the frother modifying the froth and enhancing the mechanical entrainment. Two-phase foam characterisation revealed a larger height in the blends of biopolymer and frother, which in turn promoted the mechanical entrainment in flotation. The dispersing and foaming abilities of biopolymers were governed by their structural features such as the content of functional groups, the molecular weight and counterions. This study indicates that when selecting a polymeric dispersant in flotation to deal with clay minerals, its froth property should also be taken into consideration.     

Glass-transition behaviour of plasticized starch biopolymer system – A modified Gordon–Taylor approach

Two plasticizers namely, glycerol and xylitol, based on their similar molecular size (˜6.3 Å) but different molecular weights (Glycerol-92; Xylitol-152) were selected for studying the glass-transition behaviour (rubber like behaviour) in multi-plasticized starch biopolymer with about 70% amylopectin structure. In the calorimetry measurements, glass-transition temperatures (onset temperature for bulk viscous flow) of plasticized samples were higher than non-plasticized samples at low water activities, thus showing typical antiplasticization behaviour. However, when plasticizer concentration was increased up to 15% and 20% wt, all plasticized samples showed significant reduction in glass-transition temperature. We used a modified Gordon–Taylor model to understand the competitive plasticization of glycerol and xylitol in presence of water, and suggest that competitive plasticization exists and occurs at a threshold amount of matrix free water content, due to strong three-way interactions: starch–plasticizer, plasticizer–plasticizer/water and starch–water. This competitive interaction is significant in determining the onset temperature for viscous flow behaviour; at higher matrix water content, the Gordon–Taylor constant was relatively unaffected by the plasticizer amount, and water was the dominant plasticizer. A new interaction parameter that separates the starch–plasticizer interaction in a starch–plasticizer–water system is also discussed.