The role of biomass elemental composition and ion-exchange in metal sorption by algae

The use of macroalgae, microalgae and cyanobacteria for metal sorption has been widely reported. Still, there are no studies allowing a direct comparison of the performance of these biomasses, especially while evaluating metal competition. The simultaneous sorption of Co2+, Cu2+, Ni2+ and Zn2+ present in a multi-elemental solution by six macroalgae, two microalgae and three cyanobacteria was evaluated. Brown macroalgae were shown to be the most promising biosorbent, with Undaria pinnatifida having a total metal sorption capacity of 0.6 mmol g-1. Overall, macroalgae performed better than microalgae, followed by cyanobacteria. Carboxyl groups were identified as being the main functional groups involved in metal sorption, and all biomass samples were found to be selective to Cu2+. This was linked not only to its higher complexation constant value with relevant functional groups when compared to the remaining metals, but also the Irving-Williams series. The release of K+ and Ca2+ to the aqueous solution during the metal sorption was followed. The obtained results suggest they are readily exchanged with metals in the solution, indicating the occurrence of an ion-exchange mechanism in metal sorption by most biomass. Red macroalgae are an exception to the reported trends, suggesting that their metal sorption mechanism may differ from the other biomass types.publishe

Unraveling the ecotoxicity of deep eutectic solvents using the mixture toxicity theory

The interest on deep eutectic solvents (DES) has been increasing. However, the ecotoxicological profile of DES is scarcely known. Also, despite previous studies showed that DES components dissociate in water, none assessed DES toxicity using the classical and adequate models for mixture toxicity prediction - concentration addition (CA) and independent action (IA). This study evaluates the ecotoxicological profile of DES based on [N1111]Cl, [N2222]Cl and [N3333]Cl as hydrogen bond acceptors (HBA) combined with hydrogen-bond donors (HBD) vis. ethylene glycol and 1-propanol, through the Microtox® Acute Toxicity Test. CA and IA with deviations describing synergism/antagonism, dose-ratio and dose-level effects were fitted to the toxicity data. Neither the starting materials nor DES were found hazardous to Aliivibrio fischeri, in this specific case agreeing with the claimed "green character" of DES. Among the starting materials, ethylene glycol was the least toxic, whereas [N3333]Cl was the most toxic (30 min-EC50 = 96.49 g L-1 and 0.5456 g L-1, respectively). DES toxicity followed the same trend as observed for the salts: [N1111]Cl-based DES < [N2222]Cl-based DES < [N3333]Cl-based DES. The IA model, with specific deviations, adjusted better in 5 out of 6 DES. Antagonism was observed for [N1111]Cl-based DES, and synergism for [N3333]Cl-based DES and for 1-propanol:[N2222]Cl. The application of the mixture toxicity models represents a breakthrough in the problematic of assessing the toxicity of the countless number of DES that can be created with the same starting materials, since they provide the expected toxicity of any virtual combination between HBA and HBD.publishe

Are cyanobacteria a nearly immortal source of high market value compounds?

BACKGROUND: When the human population increases, so does the need to explore a wider range of feedstocks and biomasses, such as cyanobacteria. However, a deeper understanding of the growth patterns and pigment production is required to support the selection of the most beneficial species and conditions for industrial production. The growth and pigment production (i.e., chlorophyll a and C-phycocyanin) of three cyanobacterium species were evaluated following a three-fold aim. The first goal was to compare among a species commonly selected for exploitation (Arthrospira platensis) and two alternative species (Anabaena cylindrica and Nostoc muscorum). The second goal was analyzing pigment production in the long-term. The last goal involved comparing different methods (spectrophotometry and fluorimetry) to understand whether there is an appropriate proxy of biomass increase and pigment production that can be used for monitoring purposes. RESULTS: All species showed high longevity and proved capable of growing for more than 100 days without any additional supplementation. However, the maximum quantum yield of PS II (Fv /Fm) revealed that their photosynthetic efficiency varied over time with a clear decrease after 2 months. Pigment analysis showed a heterogeneous pattern during the growth periods of all three species that could only be captured by the parameter Fv /Fm, but the pattern was only present for A. cylindrica and N. muscorum in some stages of the culture period. CONCLUSION: N. muscorum was found to be the best chlorophyll a and C-phycocyanin producer, with the production peaking for all species at defined time periods within the growth profile. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).publishe

Glycine-betaine-derived ionic liquids: Synthesis, characterization and ecotoxicological evaluation

Ionic Liquids (ILs) are generically regarded as environmentally "harmless" and thus, assumed as "non-toxic". However, due to the endless design possibilities, their ecotoxicological profile is still poorly known. An accurate knowledge on the toxicity of a substance is required, under the scope of environmental regulation worldwide, before their application and commercialization. Knowledge on the relationship between the chemical structure and toxic effects is essential for the future design of more biocompatible solvents. Focusing on the use of ILs as base lubricants, lubricant additives, or even as potential working fluids for absorption heat pumps, the knowledge on its environmental impact is of great importance, due to the possibility of spills. In this specific context, four analogues of glycine-betaine-based ILs (AGB-ILs) and four glycine-betaine based ILs (GB-ILs) were synthesized and characterized. Their ecotoxicity was assessed using representatives of two trophic levels in aquatic ecosystems, the bacteria Allivibrio fischeri (commonly used as a screening test organism) and the microalgae Raphidocelis subcapitata (as an alternative test organism that has been proven very sensitive to several IL families). The microalgae were more sensitive than the bacteria, hence, following a precautionary principle, we recommend considering the toxicity towards microalgae as an indicator in future studies regarding the focused ILs. Although four of the studied ILs were derived from a natural amino acid, all were considered hazardous for the aquatic environment, disproving the primary theory that all ILs derived from natural compounds are benign. Furthermore, the modification in the structure of anion and the cation can lead to the increase of toxicity.publishe

Uncovering the Use of Fucoxanthin and Phycobiliproteins into Solid Matrices to Increase Their Emission Quantum Yield and Photostability

In the search for a better and brighter future, the use of natural luminescent renewable materials as substitutes for synthetic ones in the energy field is of prime importance. The incorporation of natural pigments (e.g., xanthophylls and phycobiliproteins) is a fundamental step in a broad spectrum of applications that are presently marred by their limited stability. The incorporation of bio-based luminescent molecules into solid matrices allows the fabrication of thin films, which may dramatically increase the range of applications, including sustainable photovoltaic systems, such as luminescent solar concentrators or downshifting layers. In this work, we incorporated R-phycoerythrin (R-PE), C-phycocyanin (C-PC), and fucoxanthin (FX) into poly(vinyl alcohol) (PVA) and studied their optical properties. It was found that the emission and excitation spectra of the phycobiliproteins and FX were not modified by incorporation into the PVA matrix. Moreover, in the case of FX, the emission quantum yield (η) values also remained unaltered after incorporation, showing the suitability of the PVA as a host matrix. A preliminary photostability study was performed by exposing the solid samples to continuous AM1.5G solar radiation, which evidenced the potential of these materials for future photovoltaics.publishe

Bio-based solar energy harvesting for onsite mobile optical temperature sensing in Smart Cities

The Internet of Things (IoT) fosters the development of smart city systems for sustainable living and increases comfort for people. One of the current challenges for sustainable buildings is the optimization of energy management. Temperature monitoring in buildings is of prime importance, as heating account for a great part of the total energy consumption. Here, a solar optical temperature sensor is presented with a thermal sensitivity of up to 1.23% °C-1 based on sustainable aqueous solutions of enhanced green fluorescent protein and C-phycocyanin from biological feedstocks. These photonic sensors are presented under the configuration of luminescent solar concentrators widely proposed as a solution to integrate energy-generating devices in buildings, as windows or façades. The developed mobile sensor is inserted in IoT context through the development of a self-powered system able to measure, record, and send data to a user-friendly website.publishe

Potential threats of ionic liquids to the environment and ecosphere

Sem resumo disponível.publishe

Unveiling the use of hydrophobic eutectic solutions as task-specific solvents to recover bacterioruberin from Haloferax mediterranei

Haloarchaea make up a class of untapped marine microbial resources that constitute a promising source of valuable compounds with unique characteristics. Bacterioruberin is a C50 carotenoid produced by haloarchaea that possesses interesting antioxidant properties and bioactivities relevant to the food and cosmetic industries. As a substitute for the conventional organic solvents used in the extraction of nonpolar pigments, natural and biocompatible hydrophobic eutectic solvents (HES) based on the mixture of menthol with carboxylic acids were investigated for the extraction of bacterioruberin. Seven HES systems were screened both as neat solvents and in the presence of water. The menthol and levulinic acid mixture displayed a 4-fold improvement over both the ethanol control and the other HES, due to the dual action of its components. Additionally, the recovery of proteins could be achieved by the addition of water to the extract, resulting in a three-phase partition system and the formation of a protein-rich interfacial precipitate. The process intensification was assessed through the reuse of the eutectic phase over five successive extraction cycles, achieving a bacterioruberin-rich extract of 2.13 mgbacterioruberin mLHES–1. Finally, the carbon footprint of the process was determined. The results highlight the potential of HES as biocompatible solvents for the recovery of value-added compounds from marine biomass, while the use of three-phase partition allows the recovery of proteins producing a second product stream.publishe

The “bright side” of Cyanobacteria: revising the nuisance potential and prospecting innovative biotechnology-based solutions to integrate water management programs

Global warming and the anthropogenic degradation of water quality are pointed out as main causes of the worldwide increase in frequency, severity, and duration of harmful algal blooms (HABs). Cyanobacteria, major constituents of HABs, can cause ecological, economic, and human health problems, configuring a “dark side” requiring management attention. Their growth can be potentiated by climate change consequences, highlighting further the urgency of improving HABs management strategies to ensure water quality. An innovative perspective for cyanobacteria management is the exploitation of their “bright side”. Several exploitable products produced by cyanobacteria (e.g., bioactive pigments, lipids, proteins) present high market value. Thus, this work provides a critical perspective on how HABs management may be connected with biotechnology in the future. We propose the use of the biomass of cyanobacteria blooms physically removed in traditional control actions (much needed to ensure environmental and even human health safety) as a feedstock for future valorization, thus allying profit to water quality management, in a win-win relationship between economics and environmental sustainability. Such a proposal was validated with an economic analysis, which evidenced a relevant potential for a positive return (hence rendering profit likely to occur), both considering only the delivery of harvested biomass to production units and the full valuation route from harvesting to the selling of the extracted/purified product using phycocyanin as a model.publishe

The bad against the villain: suitability of Corbicula fluminea as a bioremediation agent towards cyanobacterial blooms

Cyanobacteria can cause ecological, economic and human health problems, climate change trends giving them advantage over other phytoplanktonic groups. Management strategies exist to deal with the nuisance, but many are not effective due to the likelihood of cell lysis and toxin release. This study explores the suitability of the use of the invasive and widespread bivalve Corbicula fluminea for cyanobacterial control. The capacity of clams to filter and ingest cyanobacteria was evaluated using a set of bloom-forming strains comprising different morphological features potentially affecting edibility and palatability. Results generally showed limited filtration of the majority of cyanobacteria, compared with green microalgae used as the reference for optimal filtration (ca. 60 μg Chl a removed in 120 min), except for Pseudanabaena (ca. 90 μg Chl a removed) and Anabaena (ca. 120 μg Chl a removed). The specific attention given to the binomial filtration-ingestion exposed that filtration often directly relates to the deposit of cyanobacteria as pseudofaeces rather than reflects assimilation through effective ingestion. Allocation to pseudofaeces accounted for more than 50% of the Chl a removed from water for all cyanobacteria tested. Adding to effective filtration by the clam, the related accumulation of cyanobacterial biomass in pseudofaeces has the potential for further exploitation since it can be functionally paralleled with the use of synthetic flocculants for cyanobacterial (villain) removal in settings where a natural treatment alternative using an (bad) invasive bivalve could be suitable yet controlled to avoid side ecosystem effectspublishe