Biodegradable, metal-chelating compounds as alternatives to EDTA for cultivation of marine microalgae

Iron (Fe) is an essential nutrient for microalgal metabolism. The low solubility of Fe in oxic aquatic environments can be a growth-limiting factor for phytoplankton. Synthetic chelating agents, such as ethylenediaminetetraacetic acid (EDTA), are used widely to maintain Fe in solution for microalgal cultivation. The non-biodegradable nature of EDTA, combined with sub-optimal bioavailability of Fe-EDTA complexes to microalgae, indicates opportunity to improve microalgal cultivation practices that amplify production efficiency and environmental compatibility. In the present study, the effects of four organic chelating ligands known to form readily bioavailable organic complexes with Fe in natural aquatic environments were investigated in relation to growth and biochemical composition of two marine microalgae grown as live feeds in shellfish hatcheries (Chaetoceros calcitrans and Tisochrysis lutea). Three saccharides, alginic acid (ALG), glucuronic acid (GLU), and dextran (DEX), as well as the siderophore desferrioxamine B (DFB), were compared to EDTA. Organic ligands characterized by weaker binding capacity for cationic metals (i.e., ALG, GLU, DEX) significantly improved microalgal growth and yields in laboratory-scale static batch cultures or bubbled photobioreactors. Maximal microalgal growth enhancement relative to the control (e.g., EDTA) was recorded for GLU, followed by ALG, with 20–35% increase in specific growth rate in the early stages of culture development of C. calcitrans and T. lutea. Substitution of EDTA with GLU resulted in a 27% increase in cellular omega 3-polyunsaturetd fatty acid content of C. calcitrans and doubled final cell yields. Enhanced microalgal culture performance is likely associated with increased intracellular Fe uptake efficiency combined with heterotrophic growth stimulated by the organic ligands. Based upon these results, we propose that replacement of EDTA with one of these organic metal-chelating ligands is an effective and easily implementable strategy to enhance the environmental compatibility of microalgal cultivation practices while also maximizing algal growth and enhancing the nutritional quality of marine microalgal species commonly cultured for live-feed applications in aquaculture.

Energy, Exergy and Environmental Compatibility Analyses of LPG and Household Kerosene Utilisations as Domestic Fuels in Nigeria: 1980 – 2019

Household kerosene and Liquefied Petroleum Gas form the bulk of domestic fuels, especially in Nigerian urban areas. Data on both fuels, from 1980 to 2019, were collected, mainly from Nigerian National Petroleum Corporation sources. Energy, exergy and environmental compatibility analyses were carried out on the utilisation of LPG for cooking, and household kerosene for both cooking and lighting. Kerosene lighting, with 0.05% energy efficiency and 0.045% exergy efficiency, was extremely poor. Cooking, with different mixes of both fuels, yielded energy efficiencies ranging from 35.04% to 44.54%. Corresponding exergy efficiencies were from 7.75% to 9.98%. Associated environmental compatibility factors were from 0.71749 to 0.73945. Overall process energy efficiencies, involving both cooking and lighting, were from 4.05% to 34.19%. Corresponding exergy efficiencies were from 0.93% to 7.61%. Overall environmental compatibility factors ranged from 0.71746 to 0.73259. Energy and exergy efficiencies, as well as environmental compatibility factors, increased directly with increase in LPG utilisation in the fuel-mix.

Design and Analysis of Materials’ Environmental Compatibility

The material should be in harmony with the environment during its life cycle. This article reviews the origin, concept, research status and application prospects of eco-environmental materials, discusses the environmental coordination evaluation methods of eco-environmental materials, discusses the principles and methods of environmental coordination design of various materials, and lists several typical examples of research on eco-environmental materials. It focuses on the separation and removal of impurities during the alloy regeneration cycle, as well as the organic polymer regeneration cycle technology. In this regard, this article conducts a series of analyses on the development trend of ecological environment materials.

Tungsten Disulfide-reduced GO/CNT Aerogel: A Tuned Interlayer Spacing Anode for Efficient Water Desalination

Owing to the favorable energy efficiency and environmental compatibility, capacitive deionization (CDI) has been greatly developed as a potential technology to overcome the ever-growing global water shortage. Herein, an effective...