A contribution to lipid digestion of Odobenidae family: Computational analysis of gastric and pancreatic lipases from walrus (Odobenus rosmarus divergens).

Triacylglycerols (TAGs) are a primary energy source for marine mammals during lipid digestion. Walruses (Odobenus rosmarus divergens) consume prey with a high content of long-chain polyunsaturated fatty acids; however, their digestive physiology and lipid digestion remain poorly studied. The present study aims to model and characterize the gastric (PWGL) and pancreatic (PWPL) lipases of Pacific walruses using an in-silico approach. The confident 3D models of PWGL and PWPL were obtained via homology modeling and protein threading and displayed the structural features of lipases. Molecular docking analysis demonstrated substrate selectivity for long-chain TAG (Trieicosapentaenoin; TC20:5n-3) in PWGL and short-chain TAG (Trioctanoin; TC8:0) in PWPL. Molecular dynamics simulations demonstrate that PWGL bound to tridocosahexaenoin (TC22:6n-3), the protein is considerably stable at all three salinity conditions, but fluctuations are observed in the regions associated with catalytic sites and the lid, indicating the potential hydrolysis of the substrate. This is the first study to report on the digestion of TAGs in walruses, including modeling and lipases characterization and proposing a digestive tract for pinnipeds.

Evaluation of different operational conditions in a microbial electrolysis cell inoculated with a pure culture of Shewanella oneidensis for hydrogen production.

Hydrogen is a promising alternative to meet the world's energy demand in the future because of its energetic characteristics. Microbial electrolysis cell (MEC) produces hydrogen from organic matter using exoelectrogenic bacteria. Shewanella oneidensis stands out for having the capacity to produce hydrogen using different electron transfer mechanisms. The present research aims to evaluate the hydrogen production efficiency in a MEC inoculated with a pure culture of S. oneidensis in different operational conditions. Since the use of a catalyst accounts for most of the MEC cost, no catalyst was used for anode or cathode. Experiments were performed in semi-continuous and batch mode using different electrodes, voltages applied, and medium in aerobic and anaerobic conditions. The highest hydrogen production rate (HPR) was 0.107 m3 of H2/m3day obtained in a semi-continuous experiment using graphite plates and stainless steel electrodes. In batch experiments, a HPR occurred at 0.7 V, with a value of 0.048 m3 of H2/m3day versus 0.037 m3 of H2/m3day with 0.9 V. HPR was higher with carbon felt electrode (0.056 m3 of H2/m3day). However, current density dropped after 38 h, with carbon felt electrodes, and did not recover. Results of the present research showed that the MEC using a pure culture of S. oneidensis can be considered an alternative for hydrogen production without using a catalyst. Also, S. oneidensis produced hydrogen in both anaerobic and aerobic conditions with low methane production. Optimization can be proposed to improve hydrogen production based on the operational conditions tested in these experiments.

Statistical optimization of arsenic removal from synthetic water by electrocoagulation system and its application with real arsenic-polluted groundwater.

Arsenic presence in the water has become one of the most concerning environmental problems. Electrocoagulation is a technology that offers several advantages over conventional treatments such as chemical coagulation. In the present work, an electrocoagulation system was optimized for arsenic removal at initial concentrations of 100 µg/L using response surface methodology. The effects of studied parameters were determined by a 23 factorial design, whereas treatment time had a positive effect and current intensity had a negative effect on arsenic removal efficiency. With a p-value of 0.1629 and a confidence of level 99%, the type of electrode material did not have a significant effect on arsenic removal. Efficiency over 90% was reached at optimal operating conditions of 0.2 A of current intensity, and 7 min of treatment time using iron as the electrode material. However, the time necessary to accomplish with OMS arsenic guideline of 10 µg/L increased from 7 to 30 min when real arsenic-contaminated groundwater with an initial concentration of 80.2 ± 3.24 µg/L was used. The design of a pilot-scale electrocoagulation reactor was determined with the capacity to meet the water requirement of a 6417 population community in Sonora, Mexico. To provide the 1.0 L/s required, an electrocoagulation reactor with a working volume of 1.79 m3, a total electrode effective surface of 701 m2, operating at a current intensity of 180 A and an operating cost of 0.0208 US$/day was proposed. Based on these results, electrocoagulation can be considered an efficient technology to treat arsenic-contaminated water and meet the drinking water quality standards.

Characterization of cannonball jellyfish (Stomolophus sp. 2) blue protein: a pH-stable pigment.

Pigments are present in a broad variety of terrestrial and aquatic organisms. The cannonball jellyfish (Stomolophus sp. 2) is an important fishery resource in the northwest of Mexico and is processed to be traded and consumed as seafood. During the process, water with a soluble blue pigment and other compounds are discarded to the environment. In this work, we present some properties of the blue pigment from Stomolophus sp.2 (S2bp), to decide if it could be considered as a potential value-added waste and avoid the blue proteinaceous pigment wastewater. S2bp was purified to homogeneity and had a molecular mass of 28.0 kDa; this protein exhibited a ʎmax at 650 nm, contained Zn2+ and Cu2+ metal ions, and was stable from 10 to 50 °C and in a pH range of 3.0 to 13.0 for 1 h. It had halotolerant characteristics maintaining the blue coloration in a broad range of ionic strength (0-4 M NaCl) and showed changes in ʎmax with chaotropic salts. In addition, S2bp was stable in the presence of organic acids and EDTA and in zwitterionic, anionic, and nonionic detergents at critical micellar concentration. However, oxidant reagents like NaClO and H2O2 decrease the coloration. These results show that the jellyfish pigment is a stable protein which makes it an alternative pigment for the food industry.