Argon Plasma Treatment of Tapioca Starch Using a Semi-continuous Downer Reactor

To develop a novel modification process of tapioca starch using low-pressure argon plasma treatment in a large-scale production, a semi-continuous downer reactor was designed to provide a production rate of 0.1–0.5 kg per cycle. Physicochemical and rheological properties of plasma-treated starch were investigated in order to predict the phenomena occurred during the plasma treatment. Native tapioca starch (NTS) was plasma-treated for 1, 3, or 6 cycles, which were referred to as PTS-1, PTS-3, or PTS-6 samples, respectively. Plasma treatment of the NTS resulted in a significant decrease (P?<?0.05) in paste clarity and Rapid Visco Analyzer (RVA) breakdown viscosity, and an increase in gel strength of starch. The PTS-1 had the lowest paste clarity of 39.85 %T at 650 nm and breakdown viscosity of 29.71 Rapid Visco Unit (RVU), and the highest gel strength, e.g., G′?=?5.47ω ^0.32. With increasing the number of treatment cycles, i.e., the PTS-3 and PTS-6, the paste clarity and breakdown viscosity significantly increased (P?<?0.05), while the gel strength decreased. The Fourier transform infrared (FTIR) spectroscopy via relative areas of C–O–C peaks indicated that the PTS-1 had a significant increase (P?<?0.05) in the C–O–C cross-linked bonds compared to the NTS, but the effect of depolymerization could further suppress the cross-linking reaction when the number of treatment cycle was increased. Taking an advantage of a very short residence time (less than 0.3 s) in the plasma downer reactor, the semi-continuous process of starch modification could be developed for a commercial production of non-chemically modified starch with a relatively low degree of cross-linking.     

Albacore tuna (Thunnus alalunga) spleen trypsin partitioning in an aqueous two-phase system and its hydrolytic pattern on Pacific white shrimp (Litopenaeus vannamei) shells

Partitioning behaviors of trypsin from the spleen of albacore tuna (Thunnus alalunga) in an aqueous two-phase system (ATPS) were investigated. Partitioning behaviors of proteins were influenced by polyethylene glycol (PEG) molecular mass and concentration, types and concentration of salts, NaCl concentration, and temperature. Trypsin was preferentially partitioned into the PEG-rich top phase. The best ATPS conditions for trypsin partitioning from albacore tuna spleen were 15% PEG 4000–15% NaH₂PO₄ at 40°C without the addition of NaCl, which increased the purity by 5.54-fold with the recovered activity of 71.92%. Based on SDS-PAGE, the enzyme after ATPS separation was near homogeneity and the result of SDS-substrate gel electrophoresis revealed that the band intensity of enzyme in ATPS fraction increased, indicating the enhanced specific activity of splenic extract. The study further investigated the effect of fractionated trypsin on the hydrolysis of Pacific white shrimp (Litopenaeus vannamei) shells. Electrophoretic study revealed that trypsin after ATPS separation was a potential enzyme for extraction of carotenoprotein from Pacific white shrimp shell waste. Therefore, ATPS was an effective method for purification and recovery of trypsin from the spleen of albacore tuna and it could be used as an alternative cheap proteinase for the extraction of carotenoprotein from shrimp shells.     

Effect of acrylonitrile content of acrylonitrile butadiene rubber on mechanical and thermal properties of dynamically vulcanized poly(lactic acid) blends

We report here the morphology, thermal and tensile properties of poly(lactic acid) (PLA) blends composed of acrylonitrile butadiene rubber (NBR) with different acrylonitrile contents with/without dynamic vulcanization by dicumyl peroxide (DCP). The interfacial tension of PLA and NBR measured by contact angle measurement decreased as the acrylonitrile content of NBR decreased. Likewise, SEM images showed that the rubber particle size reduced with decreasing acrylonitrile content owing to the stronger interfacial adhesion between the PLA matrix and NBR domains. Incorporation of DCP at 1.0 phr for dynamic vulcanization led to higher crosslink density and, in turn, optimal tensile strength and tensile toughness as a result of the action of PLA‐NBR copolymer as a reactive compatibilizer. The dynamic vulcanization of the blends containing low acrylonitrile NBR gave the most improved tensile properties because the free radicals from DCP decomposition preferentially attacked the allylic hydrogen atoms or double bonds of the butadiene backbone. Accordingly, more NBR macroradicals were generated and probably more PLA‐NBR copolymers were produced. Moreover, further addition of DCP at 2.0 phr provided a large amount of crosslinked NBR gel, which significantly degraded the tensile properties. From the DSC results, dynamic vulcanization lowered the cold crystallization temperature, implying an improvement of cold crystallization. Finally, TGA results showed a higher degradation temperature as a function of DCP content, which suggested that thermal stability increased due to stronger interfacial adhesion as well as higher gel content. © 2019 Society of Chemical Industry     

Biphasic scaffolds of polyvinyl alcohol with silk fibroin for oral and maxillofacial surgery based on mimicking materials design: fabrication,characterization, properties

Journal of Materials Science - Biphasic scaffolds were created based on mimicking materials design and evaluated to identify certain applications for oral and maxillofacial surgery. Polyvinyl...