Shrimp Cultured in Low-Salt Saline-Alkali Water has a Better Amino Acid Nutrition and Umami─Comparison of Flavors between Saline-Alkali Water- and Seawater-Cultured Litopenaeus vannamei.

The advantages of Litopenaeus vannamei farming in saline-alkali water have gradually attracted attention, but few studies have focused on its flavor. In this study, L. vannamei cultured in saline-alkali water (SS) and ordinary seawater (CS) (both have a breeding time of 120 days) were selected for analysis (n = 5). High-performance liquid chromatography (HPLC) was used to measure free amino acids and flavoring nucleotides in the muscles of L. vannamei, while the taste activity value (TAV) and equivalent umami concentration (EUC) were used to analyze the degree of umami. The total essential amino acids (TEAA) in the SS group were 238.41 ± 46.24 mg/mL, significantly higher than that in the CS group (107.06 ± 15.65 mg/mL). The total amount of flavor nucleotides in the SS group was 2948.51 ± 233.66 µg/mL, significantly higher than those in the CS group (2530.37 ± 114.67 µg/mL). The content and TAV of some free amino acids (Glu, Cys-s) in the SS group were significantly higher. Meanwhile, due to the significant increase in IMP, the synergistic effect of free amino acids and flavored nucleotides leads to higher EUC. The significant separation of SS and CS samples in principal component analysis (PCA) indicates a significant difference between the two groups. Our results indicate that shrimp cultured in saline-alkali water has a stronger umami. This study enriches the basic theories related to the flavor of salt-alkali water crustaceans.

Paper-Based Bipolar Electrode Electrochemiluminescence Platform Combined with Pencil-Drawing Trace for the Detection of M.SssI Methyltransferase.

Herein, a hand-drawing paper-based bipolar electrode (BPE) electrochemiluminescence (ECL) platform for M.SssI methyltransferase (M.SssI MTase) assay was proposed via employing high electrocatalytic Pt@CeO2 as an ECL co-reaction accelerator and pencil-drawing graphite electric circuits as wires and electrodes. Notably, the introduction of pencil-drawing trace not only simplified the manufacturing process but also reduced the cost and saved fabricating time. Meanwhile, Pt@CeO2 with good electrocatalytic activity and satisfactory chemical stability was used at the anode of the closed BPE-ECL device to accelerate the oxidation rate of uric acid. Due to the balanced charges of the bipolar electrode, the ECL response of the MnS: CdS@ZnS/S2O82- system emitted on the cathode was enhanced. In situ growth of gold nanoparticles in the two electrode areas was convenient for DNA immobilization. With the above points in mind, the specific DNA double strands functionalized via Pt@CeO2 were employed to identify M.SssI MTase. The unmethylated DNA double strands were cut by HpaII endonuclease, resulting in the quenching of the ECL signal. Under the optimal conditions, sensitive detection of M.SssI MTase in a wide linear range of 0.01-100 U·mL-1 with a satisfactory detection limit of 0.008 U·mL-1 was realized. The reliable and versatile BPE-ECL tool for the determination of M.SssI MTase with easy-to-operate pencil-drawing traces and independent solution systems provides a new opportunity to develop paper-based devices applied in early disease diagnosis and pathogenesis research.

Investigating COD and Nitrate-Nitrogen Flow and Distribution Variations in the MUCT Process Using ORP as a Control Parameter.

This study aimed to reveal the flow and distribution lows of chemical oxygen demand (COD) and nitrate-nitrogen under different main anoxic stage oxidation-reduction potential (ORPan) conditions based on the analysis of material balance in each reaction stage of the modified university of cape town (MUCT) process, combined with the biochemical reaction principles of activated sludge. The rule of the carbon source saving effect was also clarified. The study adopted the programmable logic controller automatic control system and the feedback control structure using the inner circulation flow of nitrate as the controlled variable. The ORPan setting values of control parameters were -140, -125, -110, -95, -70, and -60 mV, respectively. The results showed that when the ORPan setting value was -95 mV, COD distribution ratios of phosphorus-accumulating bacteria reached the highest in the anaerobic stage and preanoxic stage, with the values of 51.74 and 7.70%, respectively. The COD was distributed between heterotrophic bacteria and denitrifying bacteria in the main anoxic stage, and the distribution ratios were 4.40 and 7.19%, respectively, when the ORPan setting value was -95 mV. The study also showed the distribution of nitrate-nitrogen between denitrifying bacteria and denitrifying phosphorus-accumulating bacteria in the main anoxic stage, and when ORPan increased from -140 to -60 mV, the distribution ratios of denitrifying phosphate-accumulating bacteria increased from 76.46 to 86.32%. When there was no denitrification and phosphorus absorption, the acetic acid dosage increased from 20.33 g/d at -140 mV to 24.76 g/d at -95 mV, and the carbon source saving rate increased from 23.19 to 26.56% under similar conditions. Therefore, in the MUCT process, the regulation of ORPan changed the material flow direction and mass quality distribution of COD and nitrate nitrogen. When ORPan set value was -95 mV, COD and nitrate-nitrogen got the best distribution and the carbon source saving effect was the most significant.

A multisection passive sampler for measuring sediment porewater profile of dichlorodiphenyltrichloroethane and its metabolites.

In situ measurements of hydrophobic organic chemicals in sediment porewater, a central component in assessing the bioavailability and mobility of chemicals in sediment, have been scarce. Here, we introduce a multisection passive sampler with low-density polyethylene (LDPE) as the sorbent phase, which is appropriate for measuring vertical concentration profiles of chemicals in sediment porewater. This sampler is composed of a series of identical sampling cells insulated with seclusion rings. In each section, sorption of chemicals into LDPE is diffusion-controlled through the water layer separated from the sediment by a glass fiber filtration membrane and a porous stainless steel shield. Pilot laboratory testing indicated that the sampler can roughly determine the porewater concentrations of 1,1-dichloro-2,2-bis-(chlorophenyl)ethane (p,p'-DDD) and 1,1-dichloro-2,2-bis-(chlorophenyl)ethylene (p,p'-DDE), comparable to those yielded through centrifugation/liquid-liquid extraction, a conventional technique for sampling sediment porewater. Field deployment of the sampler was performed in an urbanized coastal region to measure the depth profiles of dichlorodiphenyltrichloroethane and its metabolites in sediment porewater. Sampling rate-calibrated and performance reference compound-calibrated concentrations were calculated, which were consistent with those obtained by the centrifugation/liquid-liquid extraction method. These results verified the utility of the sampler for measuring depth profiles of sediment porewater chemicals.