Aspartic acid introduce the functional amine groups on the surface of superparamagnetic Fe(OH)3@Fe3O4 nanoparticles for efficient immobilization of Penaeus vannamei protease.

In this study, we synthesized super magnetic Fe(OH)3@Fe3O4 nanoparticles (SPIONs) by the co-precipitation method and introduction of amine groups via chemisorption of L-aspartic acid (LAA) on the surface of SPIONs. Penaeus vannamei protease (PVP) was immobilized onto amine-functionalized supermagnetic nanoparticles (ASPIONs), and conditions affecting PVP immobilization were investigated. PVP immobilized onto ASPIONs exhibited shifts in both working optimum pH and temperature with an increase from pH 7 to pH 8, and increased optimum temperature by 10 °C compared to free enzyme. Similarly, the thermal, pH, and storage stabilities of the immobilized PVP were superior to those of free form of the enzyme. In comparison to the free enzyme, the immobilized enzyme was reusable for 15 cycles while retaining 73% of its initial activity. The Michaelis-Menten kinetic constant (Km) and maximum reaction velocity (Vmax) for free PVP were 2.3 µM and 88 µM min-1, respectively, whereas Km and Vmax values of immobilized enzyme were 2.5 µM and 85 µM min-1, respectively. These results indicated that immobilized PVP was efficient in terms of catalytic activity and can be applied to continuous casein processing applications in the different industries.

Bioconversion of shrimp waste Penaeus merguiensis using lactic acid fermentation: An alternative procedure for chemical extraction of chitin and chitosan.

Chitin extraction from shrimp wastes by biological treatment, using the Pseudomonas aeruginosa was a positive and simple method. In order to look for the optimal conditions, the wastes were incubated at 30°C and 100rpm in different glucose (0%, 10%, 15% and 20%) and inoculation (10%, 15% and 20%) concentrations for 4 and 6days. At the end of fermentation, Protease activity was investigated at different temperatures and temperature 50°C was considered as the optimum. The results obtained also showed a direct relationship between the concentration of different parameters and deproteinization and demineralization rates, so that the optimal conditions were 20% glucose, 20% inoculation and 6days fermentation. These conditions led to 82% demineralization, 92% deproteinization and chitin yield of 47%. Then, chitin was converted to chitosan using microwave, autoclave and traditional methods. The highest yield (87%) was obtained with autoclave method. At the end, the chitin and chitosan were characterized by elemental analysis and FTIR.

Chitin from Penaeus merguiensis via microbial fermentation processing and antioxidant activity.

The ability of three proteases producing bacteria such as Pseudomonas aeruginosa, Serratia marcescens, and Bacillus pumilus on the demineralization and deproteinzation efficiency of shrimp waste, for chitin extraction, was investigated. Statistical analysis of data was showed a significant difference between the percentage of demineralization and deproteinization in different bacteria species (p<0.05). The highest deproteinization (74.76%) and demineralization rate (78.46%) was obtained with P. aeruginosa and the lowest was observed in the treatment of S. marcescens. Then, chitin was converted to chitosan by deacetylation in the presence of NaOH 50%. The antioxidant activity of chitosan solution was determined using different tests. The highest activity (DO 700 nm=0.74, DO 695 nm=0.31) was observed for chitosan sample at concentration of 1,000 µg/ml. The antioxidant potential of the hydrolysates was also evaluated. The highest reducing power in a volume of 400 µl hydrolysate of S. marcescens and the highest total antioxidant capacity in a volume 100 µl hydrolysate of B. pumilus were observed. These results indicated that the P. aeruginosa bacterium in comparison with other bacterial strains, higher ability to remove proteins and mineral from shrimp waste. Therefore, the use of this bacterium is recommended for protein and mineral removal from marine crustaceans.

Polysulfone/pyrene membranes: a new microwell assay platform for bioapplications.

The use of PSU-Py prepared by click chemistry as a platform in membrane-bottom microwell plates for oxidase and hydrolase/oxidase-based enzyme assays is studied. For the GOx assay, the postulated fluorescence mechanism is based on the consumption of glucose by dissolved oxygen and GOx in the microwell plates covered with the PSU-Py membrane. For the AG-GOx assay, maltose is used as AG substrate and hydrolyzed to glucose which is then oxidized by the GOx activity. It is shown that the PSU-Py membrane acts as a fluorescence indicator of the enzymatic reactions, and both GOx and AG/GOx enzyme assays are successfully applied for glucose, maltose and acorbose analysis in the range 0.125-2.0 × 10(-3) M glucose, 0.05-0.5 × 10(-3) M maltose, and 0.0125-0.1 mg · mL(-1) acorbose, respectively.