Improving biosecurity: A necessity for aquaculture sustainability

The implementation of biosecurity measures is vital to the future development of aquaculture, if the culture of aquatic species is to make it possible to feed the global human population by 2030. Biosecurity includes control of the spread of aquatic plant and animal diseases and invasive pests, and the production of products that are safe to eat. For controls on diseases and invasive pests, it is necessary to implement programmes that involve all regional countries. Lessons from measures implemented in Asia need to be expanded/upscaled in Latin America, Africa and other emerging aquaculture regions. Such development will make countries more self sufficient and will feed local populations. Globally, there is good evidence that aquatic animal diseases and invasive animal and plant pests are being spread by hull fouling and ballast water in shipping, and serious aquatic animal diseases by the international trade in ornamental fish. While there has been a growing awareness of the danger of ballast water transfer, hull fouling remains a serious problem. It is widely recognized that ornamental fish present a disease risk, but individual countries have tried to address this alone, and there has not been an international effort to control the trade. Developments in genetics and molecular biology hold great potential for disease control, either by breeding for disease resistance, or by the use of rapid, specific, culture site testing. Currently, there is no evidence that the use of antibiotics in aquaculture poses a threat to human health or that antibiotic-resistant strains have developed; however, the future use of genetically modified aquatic organisms (GMOs) may negate the need for chemotherapy. Cultured aquatic organisms, selected for disease resistance or rapid growth, are likely to become more acceptable, and probably necessary, to feed the rapidly growing global population. Most global aquaculture occurs in developing Asian countries, in which aquaculture products can harbor zoonotic parasites, and there is a need to treat such products to negate the threat of parasitic zoonoses and permit international export. Climate change is likely to be a major influence on aquaculture in the future, with impacts on coastal aquaculture through increased sea levels affecting coastlines, and acidification. To feed the growing global population, it will be necessary to culture new species, for which research on diseases and invasiveness will be necessary to acquire the information necessary to implement biosecurity measures

Quantifying the influence of salinity on spontaneous emulsification of hydrocarbons

© 2019 Elsevier B.V. This study has investigated the process of oil-in-water spontaneous emulsification using the hydrophobic force of a non-ionic surfactant (Triton X-114) and inorganic salt additive (NaCl). The cloud point of surfactant solutions with different salt concentrations was examined and show a gradual decrease from 27 °C to 18.5 °C when increasing the salinity from 0 to 5 M. The adsorption of Triton X-114 into the oil-water interface has spontaneously enlarged the surface excess concentration of oil droplet in the system, leading to the decrease in surface tension and the spontaneous formation of oil droplets in water. Increasing the concentration of salt additive caused an increment in ions’ penetration into the hydrophilic layer of surfactants, resulting in the formation of smaller droplets. Increasing the chain-length of the oil from C7 (n-heptane) to C16 (n-hexadecane) produced a decrease of 58.6 % in droplet diameter. According, a newly-proposed model was developed and fitted against experimental data to obtain the best-fitted parameters of maximum droplet size (D0) and ion adsorbent constant (Kion). The data and modelling results verify the influence of the interfacial layer on the emulsions’ size and stability

Surface potential of the air/water interface

© 2020 by Japan Oil Chemists’ Society. The surface charge/surface potential of the air/water interface plays a key role in many natural and industrial processes. Since the first decade of the 20th century, there are many theoretical proposals to describe the surface charge in the presence of different moieties. However, a complete and consistent description of the interfacial layer remains elusive. More recently, the theoretical frameworks and experimental data get complementary support from the simulation at a molecular level. This paper reviews the recent developments from the theoretical, experimental and simulation aspects. The combined results indicated that the interaction between hydration shells of adsorbed ions and the H-bonds network of surface water plays a critical role in the ionic adsorption. The factor should be incorporated into the conventional theories to correctly predict the ion distribution near the air/water surface

Adsorption of sodium iodine at air/water interface

© 2019 Elsevier B.V. The change in surface potential was measured for NaI solutions. The modelled surface charge was then calculated and compared with molecular simulations. It was found that I− was enhanced at the air/water interface more than Na+. The result, which was confirmed by simulations, was opposite to the previous observation with NaCl. The trend is also consistent with anionic effects: larger and more polar anions adsorbed stronger at the air/water interface. The theoretical model was applied successfully to describe the changes for both systems, which are positive for NaCl and negative for NaI, respectively. The combined results of the two systems also revealed that the self-ionization of pure water induced a positive surface charge at 16.9 mV

Surface properties of the ethanol/water mixture: Thickness and composition

Ethanol is a common amphiphilic solvent often used in conjunction with water. However, despite its widespread use, key questions regarding the thickness and composition of molecules at the ethanol/water/air surface remain unclear. Recent thermodynamic analyses, Bagheri and co-authors (2016) and Santos and Reis (2018), indicated that the interfacial thickness is not constant. However, the interfacial thickness from these two analyses follows opposite trends. This study aims to provide a detailed description of the thickness and composition of the interfacial layer by combining neutron reflectivity (NR) experiments with rigorous molecular simulation. The interfacial composition was determined from molecular simulations and, in conjunction with the Gibbs excess concentration, used to calculate the interfacial thickness. It was found that the thickness decreased exponentially and reached a plateau of ~ 8.2 Å. The results confirm the trends obtained thermodynamically from surface tension. The study also provides a new theoretical framework to describe the interfacial layer of water/alcohol mixtures

Application of a cashew-based oxime in extracting Ni, Mn and Co from aqueous solution

Background: Cashew nut shell is a by-product of cashew (Anacardium occidentale) production, which is abundant in many developing countries. Cashew nut shell liquor (CNSL) contains a functional chemical, cardanol, which can be converted into a hydroxyoxime. The hydroxyoximes are expensive reagents for metal extraction. Methods: CNSL-based oxime was synthesized and used to extract Ni, Co, and Mn from aqueous solutions. The extraction potential was compared against a commercial extractant (LIX 860N). Results: All metals were successfully extracted with pH0.5 between 4 and 6. The loaded organic phase was subsequently stripped with an acidic solution. The extraction efficiency and pH0.5 of the CNSL-based extractant were similar to a commercial phenol-oxime extractant. The metals were stripped from the loaded organic phase with a recovery rate of 95% at a pH of 1. Conclusions: Cashew-based cardanol can be used to economically produce an oxime in a simple process. The naturally-based oxime has the economic potential to sustainably recover valuable metals from spent lithium-ion batteries. Graphic abstract: [Figure not available: see fulltext.

Effects of endothelin-1 and nitric oxide on glucokinase activity in isolated rat hepatocytes

To test the hypothesis that endothelin-1 (ET-1) and nitric oxide (NO) influence glucokinase (GK) activity in an opposite manner, we evaluated the effects of ET-1, L-NAME, an inhibitor of NO synthase, and L-arginine, a substrate for NO synthase, on GK activity and glycogen content in isolated rat hepatocytes. Moreover, to understand the receptor involved in the process, the effects of BQ 788, a specific antagonist of ET(B) receptor, and PD 142893, an antagonist of ET(A)-ET(B) receptors, were also evaluated. GK activity, cyclic guanosine monophosphate (cGMP), and glycogen intracellular content were measured on isolated hepatocytes, while glucose levels and NO as NO2-/NO3- were determined in the medium. High ET-1 levels induced a 20% decrease of NO2-/NO3- levels and cGMP intracellular content, followed by a 49% reduction of GK activity and a 15% decrease of glycogen. In parallel, a 10% increase of glucose in the medium was observed. In the presence of L- NAME, GK activity and glycogen levels showed analogous decrements as observed with ET-1. Also in this case, a significant decrease of the intracellular content of cGMP was observed. No synergistic effects of ET-1 and L-NAME were observed. L-Arginine was able to counteract the inhibitory effect of ET-1 on cGMP and GK activity. Glycogen content was slightly but not significantly reduced, and under those conditions, a significant decrease of glucose in the medium was observed. When hepatocytes were incubated with ET-1 plus BQ 788 or ET-1 plus PD 142893, GK activity was unchanged. Interestingly, no changes were observed in NO2-/NO3- levels and the intracellular content of cGMP was not modified when the antagonists of ET-1 receptors were added to the medium. In conclusion, the present study shows that the NO pathway seems to be an important regulator of GK activity and glycogen content through cGMP activity. In addition, ET-1 seems to be not active per se, but its activity seems mediated by a simultaneous decrease of NO levels