Kraft Lignin-Based Polyols by Microwave: Optimizing Reaction Conditions

Microwave liquefaction of precipitated Kraft lignin was carried out in polyethylene glycol (PEG) and glycerol (G) mixed with or without H₂SO₄ as catalyst. The influences of some independent variables on the yield and hydroxyl index were discussed. The viscosity, molecular distribution (GPC), and the types of volatiles measured by gas chromatography–Mass spectrometry (GC-MS) of all the liquefied products were determined. Response surface methodology (RSM) was used to optimize liquefaction conditions. Based on the results, lignin/solvents (wt%), catalyst/solvents (wt%), and reaction time were chosen as independent variables for a central composite design (CCD). The optimal liquefaction conditions were as: 20 wt% of lignin, 3 wt% of catalyst at 5 min with yield and hydroxyl number of 95.27% and 537.95 mg KOH.g^?1, respectively. Functional groups (measured by ATR-IR [attenuated total reflectance – infrared]) and the thermal degradation (TGA) of optimized bio-polyol and precipitated kraft lignin were determined.     

LIPASES AND LIPASE-CATALYZED ESTERIFICATION REACTIONS IN NONAQUEOUS MEDIA

Enzymatic reactions in nonaqueous solvents offer new possibilities for the biotechnological production of many useful chemicals using reactions that are not feasible in aqueous media. In the recent years, the use of enzymes in nonaqueous media has found applications in organic synthesis, chiral synthesis or resolution, modification of fats and oils, synthesis of sugar-based polymers, etc. The use of lipases in esterification reactions to produce industrially important products such as emulsifiers, surfactants, wax esters, chiral molecules, biopolymers, modified fats and oils, structured lipids, and flavor esters is well documented. The interest in using lipases as biotechnological vectors for performing various reactions in both macro- and microaqueous systems has picked up tremendously during the last decade. This review covers important features of lipases and lipase-catalyzed esterification reactions including the kinetics and stability of lipases, and modeling aspects.     

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.     

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.     

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.     

Characterization of antimicrobial properties on the growth of S. aureus of novel renewable blends of gliadins and chitosan of interest in food packaging and coating applications

The biocide properties of chitosan-based materials have been known for many years. However, typical antimicrobial formulations of chitosan, mostly chitosonium salts, are known to be very water sensitive materials which may impair their use in many application fields such as food packaging or food coating applications. This first work reports on the development and characterization of the antimicrobial properties of novel fully renewable blends of chitosan with more water-resistant gliadin proteins isolated from wheat gluten. Chitosan release to the nutrient broth from a wide range of blends was studied making use of the ninhydrin method. The results indicated that both pure chitosan and its blends with gliadins presented significant antimicrobial activity, which increased with increasing the amount of chitosan in the composite formulation as expected. The gliadins-chitosan blends showed good transparency and film-forming properties and better water resistance than pure chitosan. The release tests revealed that dissolution of the biocide glucosamine groups, i.e. the chitosan water soluble fractions, also increased with the amount of chitosan present in the formulation. The release of these groups was for the first time directly correlated with the antimicrobial properties exhibited by the blends. Thus, incorporation of chitosan into an insoluble biopolymer matrix was revealed as a very feasible strategy to generate novel chitosan-based antimicrobial materials with potential advantages, for instance active food packaging applications.     

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.     

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.     

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.