Product Recovery Research Articles

Enhanced production, artificial intelligence optimized three-phase partitioning extraction, and in silico characterization of extracellular neutral Bacillus cereus proteinase

The present study applied atmospheric and room temperature plasma (ARTP) mutagenesis to improve Bacillus cereus strain for neutral proteinase production. The selected improved stable strain, Phe−Tyr-ARTP-60-E demonstrated a 2.88-fold enhanced proteinase yield and 2.81-fold enhanced proteinase activity with shortened fermentation time. An artificial neural network-embedded genetic algorithm (ANN-GA) was employed to optimize the enzyme's three-phase partitioning (TPP) recovery using Python software. The optimized solution of the hybrid model recommended 38.05% wv−1 (NH4)2SO4, 1.0:2.0 crude extract/tert-butanol ratio, pH 5.84 at 23.4 °C, for the exclusive partitioning of proteinase in the intermediate phase, with 202% recovery, 13-fold purity with specific activity of 922 Umg−1. Sensitivity analysis of the model revealed that enzyme recovery was most sensitive to crude extract/tert-butanol ratio with total sensitivity (ST) of 0.253 while purification factor was most sensitive to pH with an ST of 0.444. In silico analysis using Expasy ProtParam tool revealed that mutant proteinase had 3 amino acid substitutions; Val-to-Cys; Val-to-His and Ile-to-Lys, at positions 152, 288, and 292, respectively, and 39.2 kDa molecular weight, 6.42 isoelectric point, and 33.35 instability index. The 3-Dimensional structure of the enzyme predicted by ModWeb v r273 Server revealed 39% sequence identity with Pseudoalteromonas lipolytica thermolysin. The macromolecule increased transmittance in lysozyme-coated contact lenses by 99.6% in 45 min. We conclude that ARTP mutagenesis and ANN-GA optimized TPP are effective and efficient recalcitrant strain improvement and product recovery methods, respectively. Further genetic tools and analysis of the neutral proteinase-producing gene may be required for increased improvement toward sustainable application.

Enhanced furfural extraction using neoteric hydrophobic solvents for sustainable biomass recovery and bioenergy applications

The recovery of furfural from hemicellulosic biowastes is important for developing sustainable and renewable energy alternatives to fossil fuels. However, current methods are inefficient and environmentally questionable. To address this issue, this study introduces neoteric hydrophobic solvents, specifically deep eutectic solvents (DESs) and ionic liquids (ILs). Of the 32 solvents tested, thymol:decanoic acid 1:1 (Thy:DecA) DES and trihexyltetradecyl phosphonium bis(trifluoro methylsulfonyl) imide [P14,6,6,6][NTf2] IL were the most effective, with extraction efficiencies of 94.1% and 97.1%, respectively. These solvents outperformed the reference solvent toluene, with an efficiency of 81.2%, while also showing favorable characteristics in multiple investigated criterions. For the first time, excellent performance stability was demonstrated under various operational conditions and reusability over multiple extraction and regeneration cycles. Furthermore, to provide insights into the molecular mechanisms of extraction, computational quantum chemistry modeling was employed, which showed a strong agreement with the experimental results. The development of these new neoteric solvents for furfural recovery from biowaste offers a highly effective, sustainable, and eco-friendly alternative to traditional solvents, representing a significant breakthrough in the field of renewable bioenergy production and sustainable materials recovery.

Metabolic Engineering and Process Intensification for Muconic Acid Production Using Saccharomyces cerevisiae

The efficient production of biobased organic acids is crucial to move to a more sustainable and eco-friendly economy, where muconic acid is gaining interest as a versatile platform chemical to produce industrial building blocks, including adipic acid and terephthalic acid. In this study, a Saccharomyces cerevisiae platform strain able to convert glucose and xylose into cis,cis-muconic acid was further engineered to eliminate C2 dependency, improve muconic acid tolerance, enhance production and growth performance, and substantially reduce the side production of the intermediate protocatechuic acid. This was achieved by reintroducing the PDC5 gene and overexpression of QDR3 genes. The improved strain was integrated in low-pH fed-batch fermentations at bioreactor scale with integrated in situ product recovery. By adding a biocompatible organic phase consisting of CYTOP 503 and canola oil to the process, a continuous extraction of muconic acid was achieved, resulting in significant alleviation of product inhibition. Through this, the muconic acid titer and peak productivity were improved by 300% and 185%, respectively, reaching 9.3 g/L and 0.100 g/L/h in the in situ product recovery process as compared to 3.1 g/L and 0.054 g/L/h in the control process without ISPR.

Increasing bio-hydrogen production from microbial electrolysis cell using artificial gorilla troops optimization

BackgroundThe target of this paper is to improve the performance of the microbial electrolysis cell (MEC). The performance of MEC including bio-hydrogen production and energy recovery is depending on the values of three controlling parameters including buffer concentration, dilution factor, and applied voltage.ProblemTherefore, defining the optimal values of three controlling parameters is the challenge of the work.MethodologyIn this paper the artificial gorilla troops optimization has been combined with and ANFIS modelling to increase the bio-hydrogen production from MEC. At first, using measured data, a model is created to simulate the MEC in terms of three controlling parameters. Then, for first time, an artificial gorilla troops optimization (AGTO) has been used to determine the optimal values of buffer concentration, dilution factor, and applied voltage to boost simultaneously bio-hydrogen production and energy recovery of MEC. To demonstrate the superiority of integration between ANFIS modelling and AGTO, the obtained results are compared with RSM methodology, and artificial neural network integrated with particle swarm optimization.FindingsFor hydrogen yield model, the RMSE lowered from 67.5 using RSM to 5.562 using ANFIS (decreased by 91.7%) as compared to RSM. The R-square for prediction rises from 0.94 (using RSM) to 0.99 (using ANFIS) by about 5.32%. For the ANFIS model of energy recovery, the RMSE decreased from 31.7 to 2.83 utilising ANFIS, a decrease of 91%. The R-square for prediction rises from 0.95 (using RSM) to 0.986 (using ANFIS) by about 3.8%. Compared with measured data, the integration between ANFIS and AGTO succeed to increase the hydrogen yield from 576.3 mL/g-VS to 843.32 mL/g-VS. in sum, the total performance of the MEC has been increased by 34.74%, 29.9% and 24.38% respectively compared to measured data, RSM and ANN-PSO.

Assessment of in situ product recovery techniques to enhance 2-phenylethanol production by Acinetobacter soli ANG344B

The 2-phenylethanol (2-PE) production process by the newly isolated Acinetobacter soli ANG344B is limited by product toxicity. To overcome this limitation and enhance 2-PE production process, various alternatives based in in situ product removal (ISPR) approaches were evaluated. The approaches selected for assessment were gas stripping using the air supplied to the bioreactor, liquid-liquid extraction and adsorption. Adsorption was found to be the most promising approach to increase 2-PE production. Amberlite XAD 4 was chosen from the different adsorbents tested since it has high affinity for 2-PE, being able to adsorb 205.8 ± 8.1 mg2-PE/gdry resin. In a batch cultivation process, in presence of 3 % (dry w/v) of Amberlite XAD 4, A. soli ANG344B was able to produce 6.99 ± 0.06 g/L of 2-PE with a volumetric productivity of 0.17 ± 0.00 g/L.h, which represents an improvement of 3.3-fold. To the best of our knowledge, this is the highest 2-PE production reported for a wild-type bacteria. These findings highlight the potential of Acinetobacter soli ANG344B as 2-PE producer, contributing to the development of natural 2-PE production process.

Hydrodynamic solar-driven interfacial evaporation - Gone with the flow

Evaporation has been one of the most classic desalination processes on the Earth. When we try to use the power of water flow itself, the evaporation process can perform even better. Here, we report a hydrodynamic solar-driven interfacial evaporation process which water evaporation rate can achieve 6.58 kg·m-2·h-1 (over 100 times higher than natural evaporation). A waterwheel-structure solar interfacial evaporator was designed and assembled by printed filter papers. The evaporator can both rapidly distribute solution on the evaporation interface and be hydraulically driven to rotate continuously to improve the evaporation rate by water flow. The hydrodynamic solar-driven interfacial evaporation process successfully overcomes the problem of slow diffusion of water vapor, but also realizes the day-and-night operation of process and the self-cleaning of salt fouling. Apart from the application in solar desalination, the developed evaporator has great potentials in vapor production and salt recovery for industrial use.

Riders on the storm: How do firms navigate production and market conditions amid El Niño?

This paper investigates how heavy rainfalls resulting from the 2002–03 El Niño climate pattern affect Ecuadorian firms' production and market conditions. We show that affected firms' revenue productivity (TFP-R) and markups decrease. This is due to production efficiency losses (TFP-Q) and higher marginal costs of initially less efficient firms. Decreased product output prices in response to lower product demand explain the impact on initially more efficient firms. However, the shock neither affects market shares nor survival rates of initially less efficient firms. Consequently, the productivity distribution of Ecuador's industry is not affected by the shock. We also show a swift recovery of production and market demand in the immediate aftermath of the shock. Impacts in 2002–03 are like those of the 1997–98 rainfall shock. Differentiating firms by their TFP-R rather than their production efficiency indicates firms with better (worse) market positions can mitigate the negative impacts of the shock more (less).

Recovery of Berry Natural Products using Pyrene‐based MOF Solid Phase Extraction

This work introduces a novel method of recovering bioactive berry natural products (BNPs) using solid phase extraction with metal‐organic frameworks (MOF‐SPE). Two pyrene‐based MOFs with different structural topologies, Al‐PyrMOF and Zr‐NU‐1000, were evaluated for their ability to capture and desorb BNPs, including ellagic acid, quercetin, gallic acid, and p‐coumaric acid. Time‐dependent BNP uptake via dispersive SPE revealed that NU‐1000 outperformed Al‐PyrMOF in capturing all BNPs. Our findings show NU‐1000 demonstrated a higher and more consistent BNP capture profile, achieving over 90% capture of all BNPs within 36 hours, with only a 9% variation between the most and least effectively captured BNPs. In contrast, Al‐PyrMOF, displayed a staggered uptake profile, with a significant 53% difference in capture efficiency between the most and least effectively captured BNP. However, when a BNP mixture was used at a loading concentration of 50 µg/mL, Al‐PyrMOF outperformed NU‐1000, capturing over 70% of all BNPs. Al‐PyrMOF also exhibited improved BNP recovery, with a minimum of two‐fold greater amount recovered for all BNPs. Further testing with a BNP mixture at a concentration of 15 µg/mL demonstrated that Al‐PyrMOF efficiently concentrated all BNPs, achieving a maximum extraction factor of 2.71 observed for quercetin.

Recovery and restoration of glass fibers from end‐of‐life composite waste through pyrolysis and partial oxidation processes combined with hot alkaline surface treatments

AbstractEnvironmental hazards caused by the ever‐increasing end‐of‐life (EoL) glass fiber reinforced polymer (GFRPs) composite waste is of major concern for the sustainable development of the industry. Compared to land filling or incineration, pyrolysis is one of the most promising environmentally friendly methods of disposal of EoL GFRPs. Pyrolysis not only results in recovery of clean glass fibers but other valuable products, such as oils. However, long processing time at elevated temperature leads to aggravation of already existed surface flaws along with the structural changes. Therefore, thermal conditioning of glass fibers results in severe deterioration of the strength in recovered fibers and hence limiting the use of recovered fibers to low end‐products. In this study, a new strategy was adopted where instead of complete cleaning of the fibers at pyrolysis stage, the fibers were partially oxidized and the complete removal of char from the surface of glass was done during hot alkaline etching. This strategy was opted to enhance the quality of the required fibers while reducing the processing time. The results showed ~200% increase in strength of fibers after the combined treatment of pyrolysis and post etching compared to the just pyrolyzed samples with etching time of just 1 min.Highlights End‐of‐life panels of GFRPs were pyrolyzed under inert environment of Argon. Residual char was partially removed through post oxidation under flowing air. Hot alkaline etching resulted in complete removal of char and surface defects. Partial oxidation and short etching cycles resulted in improved strength of recovered glass fibers.

Use of microalgal-fungal pellets for hydroponics effluent recycling and high-value biomass production

Hydroponic effluent (HE), enriched with inorganic nutrients, presents a viable, low-cost cultivation medium for microalgal biomass production and subsequent resource recovery. However, downstream processing, particularly biomass harvesting, remains a critical challenge for microalgal biorefineries. Therefore, the present study explored the potential of microalgal-fungal pellets (MAFP) in HE recycling for the production of biochemical-rich biomass. The optimized fungi-to-microalgae ratio (F:A) of 1:3 resulted in 100 % microalgal pelletization within 6 h. Surface characteristics suggested that metabolically active fungi with opposite charges facilitate microalgal pelletization. Further, MAFP exhibited a packed porous structure that was resilient to shear forces and had a high capacity for nutrient uptake. MAFP cultivation in HE demonstrated complete removal of ammonia-nitrogen (NH₃-N), phosphate (PO₄³⁻), and nitrate-nitrogen (NO₃⁻-N) within 7–9 days. The produced biomass was rich in biomolecules, including lipids (18.36 ± 0.12 % TS), protein (52.06 ± 2.1 % TS), and carbohydrates (28.95 ± 0.05 % TS). Besides, the high methane potential of MAFP (SMP ≈ 502.74 ± 19.1 mL CH4 g−1 VS, and TMP ≈ 817.68 ± 12.5 mL CH4 g−1 VS) indicated its suitability for biogas production. In essence, MAFP offers efficient HE recycling and biochemically rich biomass production, advancing towards a green and circular bioeconomy.

Spatial heterogeneity in post-fire vegetation productivity recovery and its drivers

Spatial heterogeneity in post-fire vegetation productivity recovery and its drivers

Harnessing the power of module markets for effective product recovery strategies

AbstractThis paper investigates how product modularity affects a manufacturer's recovery strategy by constructing two trade‐in models: one with a module market and another without. Our results reveal that opening a module market is not always profitable for the manufacturer, except when the module production cost is extremely low. When opening it is less profitable, the manufacturer can boost profits by raising the module price, increasing salvage value, and reducing costs through remanufacturing. Regarding collection quantity, our findings reveal that a module market, particularly with high module costs and durability, increases trade‐in quantity, challenging the conventional expectations of market share erosion.

Main Directions of Modern Transformation and Modernization of Russian Society, Ways to Overcome the Systemic Crisis in the Context of Technological Revolution: Alternative Strategic Development Models

At the present stage of Russia’s development in the prevailing historical conditions, a period of deep conceptual transformations has begun, measures are being taken to free it from its continued dependence on crisis global processes, from the globalism policy of developed imperialist countries. Today, after three periods of permanent systemic crisis, through which Russia went from the early 80s to the early 2000s, the country is emerging from this dependence, returning to its mental ideological and cultural foundations, to state-political, economic, scientific, technical and technological sovereignty, to the status of a world power, renewed civilization, towards the consolidation of society. This period is characterized as a period of transformation and new modernization of society. The article, based on new approaches and methods of a comprehensive historical, sociological and formational-civilizational analysis of the problems of society’s development, examines the issues of the new modernization of society that has begun, analyzes and evaluates the persistent manifestations of the systemic crisis, issues of implementing an innovative anti-crisis management strategy, strategic planning and strategic management. Possible forecasts and alternatives for social development are considered. These processes require a clear, meaningful choice and implementation of a long-term strategy for the dynamic, innovative development of knowledge-intensive sectors of the economy, labor productivity growth, production recovery based on new reindustrialization and the industrial revolution, the development and implementation of achievements of the fifth technological order, scientific, technical, technological, information revolution, the formation of new scientific, human resources, including in the areas of governance of society and the state, ensuring comprehensive security and sovereignty of society and the state, regulatory support for these processes. This implies the choice of a new socio-economic, formational and civilizational model for further progressive development, taking into account positive domestic and foreign experience, and the corresponding ideological basis for these transformations. All this is becoming an urgent issue for the entire spectrum of social and social sciences, for educational practices.

A novel method for non-destructive efficient green recovery of multiple high value products from microalgal cells with enzymatically enhanced permeability

A method is developed for simultaneous extraction of lipids, hydrocarbons and carotenoids from primary algal biomass without the need for cell sacrifice. Enzymatically predigested cells (from previous experiments) with enhanced permeability were used, for ‘milking’ with biocompatible solvent. The continuous non-destructive extraction of lipids and carotenoids from an improved permeabilized microalgal cell using crude enzyme concoctions and biocompatible solvents has not been reported so far. Oocystis sp. cells showed considerable viability following enzymatic pretreatment and extraction using dodecane which was verified through cell viability assays, and chlorophyll content. HPLC analysis confirmed the presence of lutein and zeaxanthin. GC-MS analysis showed the presence of omega-3 alpha linolenic acid, PUFAs, and phenolics, in enzymatically digested microalgal cells. The content of fatty acids and esters in enzyme treated samples was 57.18 %, and the enzyme with dodecane treated samples showed 31.4 % fatty acids and esters content. Omega-3 linolenic acid comprised 11.66 % in enzyme treated cells and showed a marginal increase of 12.5 % in enzyme with dodecane treated cells. The method enables recovery of multiple compounds from a single biomass. In the present study, a cultivation strategy of microalgal cells with enhanced permeability, grown in biocompatible solvent is proposed, whereby maximum yield of multiple valuable metabolites can be obtained from a single biomass. The method simplifies downstream processing operations by circumventing cell harvesting and drying. The use of green extraction solvents reduces the overall carbon footprint of the process.

Combination of magnetite and sodium percarbonate to enhance acetate-enriched short-chain fatty acids production during sludge anaerobic fermentation

Large amounts of waste activated sludge are generated daily worldwide, posing significant environmental challenges. Anaerobic fermentation is a promising method for sludge disposal, but it has two technical bottlenecks: the availability of short-chain fatty acids (SCFAs)-producing substrates and SCFAs consumption by methanogenesis. This study proposes a pretreatment strategy combining sodium percarbonate (SPC) and magnetite (Fe3O4) to address these issues. Under optimized conditions (20 mg Fe3O4/g TSS and 15 mg SPC/g TSS), SCFAs production increased to 3244.10 ± 216.31 mg COD/L, about 3.06 times the control (1057.29 ± 35.06 mg COD/L) and surpassing reported treatments. The combined pretreatment enhanced the disruption of extracellular polymeric substances, increased the release of biodegradable matters, improved acidogenesis enzyme activities, and inhibited methanogenesis. Additionally, it increased NH4+-N release in favor of the recovery of phosphorus from sludge residual. This study demonstrates an efficient pretreatment for high SCFAs production and resource recovery from WAS.

A Carrier Phase Ultrafiltration and Backflow Recovery Technique for Purification of Biological Macromolecules.

A simple carrier phase based ultrafiltration technique that is akin to liquid chromatography and is suitable for medium-to-large volume sample preparation in the laboratory is discussed in this paper. A membrane module was integrated with a liquid chromatography system in a "plug and play" mode for ease of sample handling, and recovery of species retained by the membrane. The sample injector and pump were used for feed injection and for driving ultrafiltration, while the sensors and detectors were used for real-time monitoring of the separation process. The concentration of retained species was enriched by utilizing controlled concentration polarization. The recovery of the retained and enriched species was enhanced by backflow of carrier phase through the membrane using appropriate combination of valves. The backflow of carrier phase also cleaned the membrane and limited the extent of membrane fouling. Proof-of-concept of the proposed technique was provided by conducting different types of protein ultrafiltration experiments. The technique was shown to be suitable for carrying out protein fractionation, desalting, buffer exchange and concentration enrichment. Adoption of this approach is likely to make ultrafiltration easier to use for non-specialized users in biological research laboratories. Other advantages include enhanced product recovery, significant reduction in the number of diavolumes of buffer needed for conducting desalting and buffer exchange, minimal membrane fouling and the potential for repeated use of the same module for multiple separation cycles.

A preliminary evaluation of how classical separation techniques affect the solid catalyst surface features during transesterification

The aim of this study was to investigate how the classical separation methods alter the solid catalyst surface structure in heterogeneous-catalyzed transesterification, viz., centrifugal and gravitational settling-in-funnel schemes, for the first time. The FTIR spectroscopy showed that while the settling system produces vivid and smooth surface shifting as a result of long-term contact with reaction products, centrifugal separation does not entirely obliterate the identity of the post-reaction catalyst surface. In addition, the SEM analysis confirmed that smaller agglomerates, which may have resulted from the dissolution of some particles and the accumulation of organic substances that clog the catalyst pore through the formation of calcium-glycerol bonds during the decantation period, were observed in the gravitational settling system; this trait could also complicate the separation and lower the desired product recovery (biodiesel). Whereas the centrifugal separation technique revealed the presence of bigger oval-shaped agglomerates, which are anticipated to possess more unoccupied active sites for efficient catalysis. As a result, centrifugal separation produces a greater biodiesel yield (87 ± 0.9%) than the settling method (76.6 ± 2%). The fuel properties of biodiesel products were characterized in terms of acid value, kinematic viscosity, cetane number, and specific gravity, of which only the cetane number does not meet the international limit due to its aromatic content. Generally, the results of this study proved that centrifuges are a more effective method of separating heterogeneous catalysts relative to the decantation system.

Exploring the efficient catalytic decomposition behavior of AsH3 over HZSM-5 molecular sieve based on in situ DRIFTS characterization

Existing processes for transforming arsine (AsH3) into toxic arsenic oxides (AsxOy) through catalytic oxidation do not meet economic requirements. In contrast, the catalytic decomposition method stands out due to its ability to both remove AsH3 and obtain elemental arsenic (As0) as a valuable product. A series of blank molecular sieves (HZSM-5, 13X, MCM-41, and TS-1) was applied to the catalytic decomposition performance of AsH3. At a catalytic decomposition temperature of 100 ℃, the HZSM-5 zeolite exhibited exceptional performance, achieving a D90% value (the duration for which the AsH3 removal efficiency remained above 90 %) exceeding 40 h. Moreover, up to 83.1 % of the product was As0. Comprehensive characterization revealed that the surface of the HZSM-5 zeolite contained a large number of strong acid sites, which played a key role in As0 generation. In situ diffuse reflectance infrared spectroscopy further revealed the activation behavior of O2 at the Brønsted acid sites on HZSM-5. To assess its suitability in industrial applications, the AsH3 removal performance of the HZSM-5 molecular sieve was investigated in the presence of actual gas components (CO, H2S, PH3). This study provides new ideas for the effective catalytic decomposition of AsH3 and the recovery of valuable products in industry.

Global patterns and drivers of post-fire vegetation productivity recovery

Global patterns and drivers of post-fire vegetation productivity recovery

Primary productivity recovery and shallow-water oxygenation during the Sturtian deglaciation in South China

The Cryogenian Period (ca. 720–635 Ma) marks a key node in Earth's history, characterized by two global glaciations when the paleo-tropical regions were covered by glaciers, namely the Sturtian and Marinoan Snowball Earth events. Within the Cryogenian, the evolution of primary producers persisted, evidenced by the worldwide discovery of diverse microfossils and the proliferation of algae in the interglacial oceans. The Cryogenian radiation of algae facilitated the emergence and evolution of early eumetazoan animals. However, the paleoredox reconstruction of the interglacial Cryogenian presents more challenges. The open oceans were predominantly and permanently ferruginous throughout the Cryogenian Period, and persistently euxinic conditions developed in restricted basins, such as the Nanhua Basin. Some of the studies suggested a possible fully‑oxygenated interval in the aftermath of the Sturtian glaciation. Therefore, a knowledge gap lies between the biological prosperity and severe habitability in the interglacial oceans. In order to fill this gap, we report a newly discovered interglacial deposition – the Datangpo Formation – of shallow water depth from the Guitouwan section, Shennongjia area, South China. A combination of iron speciation, total organic matter (TOC), and pyrite sulfur isotopes (δ34Spy) analyses are conducted, along with numerical simulations, for reconstructions of paleoredox conditions and paleoproductivity level. Additionally, we collected Fe chemistry, TOC, and pyrite sulfur data from multiple successions of the Datangpo Formation in South China to reconstruct the paleoredox landscape. The spatial TOC comparison suggests that the interglacial interval is marked by a TOC increase at the base, and the Guitouwan succession represents the early deposition during the wake of Sturtian deglaciation. Fe speciation suggests locally (dys)oxic-ferruginous condition in the Shennongjia area, while the δ34Spy systematics indicate a transition from ferruginous to euxinic condition and a sharp increase in primary productivity during the Sturtian deglaciation. With respect to the high δ34Spy values, the observed discrepancy suggests that the iron proxy might be inapplicable during fast environmental changes, especially during the deglaciation episodes. The comparison of Fe chemistry and pyrite sulfur isotopes between different water-depth settings informs a redox-stratified ocean in the Nanhua Basin. The newly discovered interglacial deposition fills the blank in understanding the shallow-water oxygenation in the Sturtian glacial aftermath, recording the transition from (dys)oxic-ferruginous to ferruginous-euxinic and from low to high productivity levels. These findings shed new light on the interpretation of Fe chemistry and δ34Spy in the geological past, and provide a novel perspective on investigating productivity levels.