First and second line mechanisms of cadmium detoxification in the lichen photobiont Trebouxia impressa (Chlorophyta)

“First line” defence mechanisms, such as phytochelatin biosynthesis, and “second line” mechanisms, such as stress protein induction, were investigated in cadmium-exposed cells of Trebouxia impressa Ahmadjian, a green microalgal species that is a common photobiont of the lichen Physcia adscendens (Fr.) H. Olivier. When T. impressa cells were exposed to 0, 9 and 18 μM Cd for 6, 18 and 48 h, glutathione and phytochelatins efficiently protected the cells against Cd damage. By contrast, the highest Cd concentration (36 μM) at the longest exposure-time (48 h) caused marked drops in glutathione and phytochelatin content, several types of ultrastructural damage, and decreases in cell density and total chlorophyll concentration. In this case, induction of stress proteins was observed, but only long after the induction of phytochelatins. Thus, stress proteins could represent a “second line” mechanism to counteract Cd stress, activated when there is a decline in the “first line” mechanism of Cd detoxification given by phytochelatins.     

Effect of nitrogen supply on photosynthesis and carbonic anhydrase activity in the green seaweed Ulva rigida (Chlorophyta)

Photosynthesis rate and carbonic anhydrase (CA) activity have been studied in the green seaweed Ulva rigida C. Agardh (Chlorophyta) grown in seawater (SW) and SW supplemented with 40 M NH₄Cl (N-SW). Higher growth and maximal O₂ evolution rates were observed in N-SW- than in SW-grown sea-weeds. Western blot analysis of the total homogenates probed with antibodies raised against small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) showed crossreaction with a 15 kdalton polypeptide in both SW- and N-SW-grown plants, although the band was more intense in N-SW-grown plants. Carbonic anhydrase activities in the total homogenate and in the soluble protein fraction were higher in N-SW-grown plants. Although the pellets from both plants showed a considerable CA activity, the activity of CA in the thylakoid membranes was undetectable. The low nitrogen concentration is a major environmental factor that affects the level of RuBisCO and CA, and therefore CO₂ assimilation in U. rigida.     

Genetic diversity and genetic differentiation of Squaliobarbus curriculus from the Pearl River based on mitochondrial D-loop sequences北大核心CSCD

Squaliobarbus curriculus is one of the most economically important edible freshwater fish in the Pearl River. To assess the level of genetic diversity and genetic variation of S. curriculus populations w ithin t he Pearl R iver, samples were collected from six geographical populations from six drainages. 978 base pairs of the D-loop sequence were obtained as a molecular marker. 106 haplotypes were defined among 170 S. curriculus individuals. Populations of S. curriculus in the Pearl River displayed a high haplotypic diversity index (h = 0.9820) and high nucleotide diversity index (π = 0.01353). T he results of genetic distance and genetic differentiation index show that genetic differentiation among S. curriculus populations is not significant. The neighbor-joining tree shows two clades. Clade A is composed of most haplotypes of S. curriculus. Clade B includes two private haplotypes from the Xijiang River. Haplotype network analysis is consistent with the results of genetic distance and genetic differentiation. The results of AMOVA analysis showed that most variation was found within populations (99.36%). Neutral test analysis explained that there was population expansion in the history of S. curriculus in the Pearl River. Xijiang River could be the center of origin, as supported by all the results. © 2018 Science Press. All rights reserved.     

Use of flyash as environmental and agronomic amendments

Coal combustion power plant flyash materials have been reported as useful soil amendments with agronomic and environmental benefits. This paper reports the efficacy of fluidized bed combustion (FBC) and flue gas desulfurization (FGD) byproducts, when amended with dairy, swine, and broiler litter manures, in reducing phosphorus (P) solubility and potential impact on water quality. At a rate of 400 g/kg, FBC reduced water soluble P by 60% for dairy and swine and 50% for broiler litter, as compared to un-treated control samples. Byproduct FGD had little effect when amended into dairy manure, but reduced water soluble P by nearly 80% when amended into swine and broiler manure at a rate of 250 g/kg. The amount of Ca added in the amendments together with pH of the mixture is the major contributing factor in soluble P reduction. Sequential extraction results showed that the flyash treatments shifted water soluble P into mainly bicarbonate extractable P. The latter is still considered available for crop uptake but less vulnerable for environmental losses. Coal combustion byproducts, when amended into manure and used properly, can provide a useful and viable option for improving nutrient management on animal farms.     

Enhancement of MK-7 synthesis by engineered strains of Bacillus subtilis natto that overexpress men genes and by increasing available dissolved oxygen北大核心CSCD

In recent years, researchers have discovered novel physiological functions of vitamin K2. In addition to promoting blood clotting, it can prevent osteoporosis and cardiovascular disease and is expected to treat some tumors and Parkinson’s disease. Bacillus subtilis natto is a probiotic that has been approved by the U.S. Food and Drug Administration for use as a bioproducer of vitamin K2. Its product’s main form is MK-7, which has a long half-life in the human body and high bioavailability. Bacillus subtilis natto displays great potential for large-scale biological preparation of vitamin K2. In this study, the Sipizizen method of Bacillus subtilis transformation was optimized to make it suitable for molecular transformation of Bacillus subtilis natto. Vectors for overexpression of all 8 genes involved in the menadione synthetic pathway were constructed, and changes in MK-7 fermentation yield after transformation of Bacillus subtilis natto were investigated. Three enzymes were found to exert significant effects on MK-7 synthesis, namely isopentenyltransferase (MenA), 1,4-dihydroxy-2-naphthoyl-CoA synthase (MenB), and nornaphthoquinone methyltransferase (MenG). A modified strain (BN-pABG) with higher MK-7 productivity was obtained by concerted overexpression of menA, menB, and menG. In a 5 L bioreactor, MK-7 synthesis was further enhanced by optimizing oxygen supply. The final yield of MK-7 from the modified strain was 62.21 mg/L, 1.26 times higher than that of the original strain. These results show that combined overexpression of menA, menB, and menG strongly promotes MK-7 synthesis by Bacillus subtilis natto, and optimizing the oxygen supply conditions also promotes more robust MK-7 synthesis. © 2022 Authors. All rights reserved.     

Metal contents of fish from cultureponds near scrap metal reclamation facilities

Milkfish (Chanos chanos) from four fish-culture ponds adjacent to different metal recovery facilities along the Er-Jen River area, Tainan, Taiwan, were sampled to determine their metal contents. Chemical analysis showed that fish tissue contained different concentrations of Cu: 0.71-6.37 micrograms/g, Pb: ND (not detectable) approximately 41.04 micrograms/g, Cd: ND approximately 0.41 microgram/g, Al: 6.75-64.11 micrograms/g, Ni: 0.062-0.504 microgram/g and Zn: 16.11-41.86 micrograms/g. The average concentrations of Cu, Al, Zn, Cd and Pb in fish samples from some of the ponds were significantly higher than those from the reference pond. In addition, there were variations in metal concentrations of fish collected from different ponds. Pond D had the highest mean values of Cu, Cd and Zn, and Pond B of Al and Pb. Further investigations are needed to determine the source of metal contamination in the fish.     

Experimental investigation of gas explosion in single vessel and connected vessels

Gas explosion in connected vessels usually leads to high pressure and high rate of pressure increase which the vessels and pipes can not tolerate. Severe human casualties and property losses may occur due to the variation characteristics of gas explosion pressure in connected vessels. To determine gas explosion strength, an experimental testing system for methane and air mixture explosion in a single vessel, in a single vessel connected a pipe and in connected vessels has been set up. The experiment apparatus consisted of two spherical vessels of 350 mm and 600 mm in diameter, three connecting pipes of 89 mm in diameter and 6 m in length. First, the results of gas explosion pressure in a single vessel and connected vessels were compared and analyzed. And then the development of gas explosion, its changing characteristics and relevant influencing factors were analyzed. When gas explosion occurs in a single vessel, the maximum explosion pressure and pressure growth rate with ignition at the center of a spherical vessel are higher than those with ignition on the inner-wall of the vessel. In conclusion, besides ignition source on the inner wall, the ignition source at the center of the vessels must be avoided to reduce the damage level. When the gas mixture is ignited in the large vessel, the maximum explosion pressure and explosion pressure rising rate in the small vessel raise. And the maximum explosion pressure and pressure rising rate in connected vessels are higher than those in the single containment vessel. So whenever possible, some isolation techniques, such as fast-acting valves, rotary valves, etc., might be applied to reduce explosion strength in the integrated system. However, when the gas mixture is ignited in the small vessel, the maximum explosion pressures in the large vessel and in the small vessel both decrease. Moreover, the explosion pressure is lower than that in the single vessel. When gas explosion happens in a single vessel connected to a pipe, the maximum explosion pressure occurs at the end of the pipe if the gas mixture is ignited in the spherical vessel. Therefore, installing a pipe into the system can reduce the maximum explosion pressure, but it also causes the explosion pressure growth rate to increase.     

Methods for more accurate determination of explosion severity parameters

Accurate determination of explosion severity parameters (p_max, (dp/dt)_max, and K_St) is essential for dust explosion assessment, identification of mitigation strategy, and design of mitigation measure of proper capacity. The explosion severity parameters are determined according to standard methodology however variety of dust handled and operation circumstances may create practical challenge on the optimal test method and subsequent data interpretation. Two methods are presented: a statistical method, which considers all test results in determination of explosion severity parameters and a method that corrects the results for differences of turbulence intensity. The statistical method also calculates experimental error (uncertainty) that characterises the experimental spread, allows comparison to other dust samples and may define quality determination threshold. The correction method allows to reduce discrepancies between results from 1 m³ vessel and 20-l sphere caused by difference in the turbulence intensity level. Additionally new experimental test method for difficult to inject samples together with its analysis is described. Such method is a versatile tool for explosion interpretation in test cases where different dispersion nozzle is used (various turbulence level in the test chamber) because of either specific test requirements or being “difficult dust sample”.     

An integrated approach to assessing the environmental and health impacts of pollution in the urban environment: Methodology and a case study

This paper presents a new decision-support methodology and software tool for sustainable management of urban pollution. A number of different methods and tools are integrated within the same platform, including GIS, LCA, fate and transport modelling, health impact assessment and multi-criteria decision analysis. The application of the framework is illustrated on a case study which investigates the environmental and health impacts of pollution arising from different industrial, domestic and transport sources in a city. The example city chosen for the study is Sheffield, UK, and the main pollutants considered are NO_x, SO₂ and PM10. The results suggest that the absence of the current large industrial sources in the city would lead to a 90% reduction of the SO₂ and 70% of the NO₂ ground concentrations, consequently preventing 27 deaths and 18 respiratory hospital admissions per annum for a population of 500,000. Based on the total annual mortality and hospital admissions in Sheffield for the year of the assessment, this means that 0.53% of premature deaths and 0.49% of respiratory hospital admissions would be prevented by the estimated reduction in air pollution.