Sustainable Recovery of Platinum Group Metals from Spent Automotive Three-Way Catalysts through a Biogenic Thiosulfate-Copper-Ammonia System.

This study explores an eco-friendly method for recovering platinum group metals from a synthetic automotive three-way catalyst (TWC). Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods. Biogenic thiosulfate production was optimized in a gas-lift bioreactor by studying the pH (8-10) and operation modes (batch and continuous) under anoxic and microaerobic conditions for 35 d.

Bioleaching of the α-alumina layer of spent three-way catalysts as a pretreatment for the recovery of platinum group metals.

Acid bioleaching of Al by Acidithiobacillus thiooxidans has been explored as an environmentally friendly pretreatment to facilitate the extraction of platinum group metals from spent three-way catalysts (TWC). Biogenic sulfur obtained from desulfurization bioreactors improved the production of acid by A. thiooxidans compared to commercially available elemental sulfur.

Metabolomics of for Disclosing Novel Metabolic Engineering Strategies for Enhancing Hydrogen and Ethanol Production.

The biological production of hydrogen is an appealing approach to mitigating the environmental problems caused by the diminishing supply of fossil fuels and the need for greener energy. is one of the best-characterized microorganisms capable of consuming glycerol-a waste product of the biodiesel industry-and producing H and ethanol. However, the natural capacity of to generate these compounds is insufficient for commercial or industrial purposes.

Automatable downstream purification of the benzohydroxamic acid D-DIBOA from a biocatalytic synthesis.

Herbicides play a vital role in agriculture, contributing to increased crop productivity by minimizing weed growth, but their low degradability presents a threat to the environment and human health. Allelochemicals, such as DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4 H)-one), are secondary metabolites released by certain plants that affect the survival or growth of other organisms. Although these metabolites have an attractive potential for use as herbicides, their low natural production is a critical hurdle.

Metabolomics for the design of new metabolic engineering strategies for improving aerobic succinic acid production in Escherichia coli.

Introduction: Glycerol is a byproduct from the biodiesel industry that can be biotransformed by Escherichia coli to high added-value products such as succinate under aerobic conditions. The main genetic engineering strategies to achieve this aim involve the mutation of succinate dehydrogenase (sdhA) gene and also those responsible for acetate synthesis including acetate kinase, phosphate acetyl transferase and pyruvate oxidase encoded by ackA, pta and pox genes respectively in the ΔsdhAΔack-ptaΔpox (M4) mutant. Other genetic manipulations to rewire the metabolism toward succinate consist on the activation of the glyoxylate shunt or blockage the pentose phosphate pathway (PPP) by deletion of isocitrate lyase repressor (iclR) or gluconate dehydrogenase (gnd) genes on M4-ΔiclR and M4-Δgnd mutants respectively.

Development and validation of a sampling and analysis method to determine biogenic sulfur in a desulfurization bioreactor by gas chromatography coupled with a pulsed flame photometric detector (GC-PFPD).

Suspended biomass bioreactors can be operated to remove HS from biogas under anoxic conditions and produce elemental sulfur, the commercial value of which has been demonstrated. In the present paper, a novel methodology comprising the optimization of a determination method performed in a gas chromatograph equipped with a pulsed flame photometric detector (GC-PFPD), combined with a simple preparation based on filtration and extraction with toluene, is proposed. The injector temperature and carrier gas flow rate (Q) values were optimized using a response surface methodology based on a face-centred composite central design.

Integration of a nitrification bioreactor and an anoxic biotrickling filter for simultaneous ammonium-rich water treatment and biogas desulfurization.

A preliminary assessment has been carried out on the integration of an anoxic biotrickling filter and a nitrification bioreactor for the simultaneous treatment of ammonium-rich water and HS contained in a biogas stream. The nutrient consumption in the biotrickling filter was as follows (mol NO-N): 6.3·10 ± 1.

Identification of Enzymatic Bottlenecks for the Aerobic Production of Malate from Glycerol by the Systematic Gene Overexpression of Anaplerotic Enzymes in .

The biotechnological production of dicarboxylic acids (C4) from renewable carbon sources represents an attractive approach for the provision of these valuable compounds by green chemistry means. Glycerol has become a waste product of the biodiesel industry that serves as a highly reduced carbon source for some microorganisms. is capable of consuming glycerol to produce succinate under anaerobic fermentation, but with the deletion of some tricarboxylic acid (TCA) cycle genes, it is also able to produce succinate and malate in aerobiosis.

Effect of two different intermediate landfill leachates on the ammonium oxidation rate of non-adapted and adapted nitrifying biomass.

A widely employed approach to minimize the detrimental effect of landfill leachates (LL) on nitrifying biomass is to adapt it to these contaminated effluents prior to use. In the study reported here the impact of different intermediate landfill leachates (intermediate 1 (ILL1) and intermediate 2 (ILL2)) and synthetic medium (SM) on the nitritation rates of non-adapted and adapted nitrifying biomass were evaluated and modeled. The models, based on previously reported models (Haldane, Edwards and Aiba), considered the effect of three different heavy metals (Cu, Ni and Zn) present in both landfill leachates.

Optimization of the Biocatalysis for D-DIBOA Synthesis Using a Quick and Sensitive New Spectrophotometric Quantification Method.

D-DIBOA (4-hydroxy-(2H)-1,4-benzoxazin-3-(4H)-one) is an allelopathic-derived compound with interesting herbicidal, fungicidal, and insecticide properties whose production has been successfully achieved by biocatalysis using a genetically engineered strain. However, improvement and scaling-up of this process are hampered by the current methodology for D-DIBOA quantification, which is based on high-performance liquid chromatographic (HPLC), a time-consuming technique that requires expensive equipment and the use of environmentally unsafe solvents. In this work, we established and validated a rapid, simple, and sensitive spectrophotometric method for the quantification of the D-DIBOA produced by whole-cell biocatalysis, with limits of detection and quantification of 0.

Anoxic biogas biodesulfurization promoting elemental sulfur production in a Continuous Stirred Tank Bioreactor.

Biological desulfurization of biogas has been extensively studied using biotrickling filters (BTFs). However, the accumulation of elemental sulfur (S°) on the packing material limits the use of this technology. To overcome this issue, the use of a continuous stirred tank bioreactor (CSTBR) under anoxic conditions for biogas desulfurization and S° production is proposed in the present study.

Characterization of eubacterial communities by Denaturing Gradient Gel Electrophoresis (DGGE) and Next Generation Sequencing (NGS) in a desulfurization biotrickling filter using progressive changes of nitrate and nitrite as final electron acceptors.

Anoxic biotrickling filters (BTFs) represent a technology with high HS elimination capacity and removal efficiencies widely studied for biogas desulfurization. Three changes in the final electron acceptors were made using nitrate and nitrite during an operating period of 520 days. The stability and performance of the anoxic BTF were maintained when a significant perturbation was applied to the system that involved the progressive change of nitrate to nitrite and vice versa.

A genetically engineered Escherichia coli strain overexpressing the nitroreductase NfsB is capable of producing the herbicide D-DIBOA with 100% molar yield.

Background: The use of chemical herbicides has helped to improve agricultural production, although its intensive use has led to environmental damages. Plant allelochemicals are interesting alternatives due to their diversity and degradability in the environment. However, the main drawback of this option is their low natural production, which could be overcome by its chemical synthesis.

Metabolic engineering for the optimization of hydrogen production in Escherichia coli: A review.

Hydrogen is a potential sustainable energy source and it could become an alternative to fossil fuel combustion, thus helping to reduce greenhouse gas emissions. The biological production of hydrogen, instead of its chemical synthesis, is a promising possibility since this process requires less energy and is more sustainable and eco-friendly. Several microorganisms have been used for this purpose, but Escherichia coli is one of the most widely used in this field.

Overexpression of the nitroreductase NfsB in an E. coli strain as a whole-cell biocatalyst for the production of chlorinated analogues of the natural herbicide DIBOA.

Benzohydroxamic acids, such as DIBOA (2,4-dihydroxy-2 H)-1,4-benzoxazin-3(4 H)-one), are plant products that exhibit interesting herbicidal, fungicidal and bactericidal properties. A feasible alternative to their purification from natural sources is the synthesis of analogous compounds such as D-DIBOA (2-deoxy-DIBOA) and their chlorinated derivatives. Their chemical synthesis has been simplified into two steps.

A comparative study of eubacterial communities by PCR-DGGE fingerprints in anoxic and aerobic biotrickling filters used for biogas desulfurization.

Biological desulfurization has proven to be a process that is technically and economically feasible on using biotrickling filters that can be performed under aerobic and anoxic conditions. However, microbial communities are different mainly due to the use of different final electron acceptors. The analysis of microbial communities in these systems has not been addressed with regard to the anoxic process.

Heterologous expression of the human Phosphoenol Pyruvate Carboxykinase (hPEPCK-M) improves hydrogen and ethanol synthesis in the Escherichia coli dcuD mutant when grown in a glycerol-based medium.

The production of biodiesel has emerged as an alternative to fossil fuels. However, this industry generates glycerol as a by-product in such large quantities that it has become an environmental problem. The biotransformation of this excess glycerol into other renewable bio-energy sources, like H and ethanol, by microorganisms such as Escherichia coli is an interesting possibility that warrants investigation.

Effect of gas-liquid flow pattern and microbial diversity analysis of a pilot-scale biotrickling filter for anoxic biogas desulfurization.

Hydrogen sulfide removal from biogas was studied under anoxic conditions in a pilot-scale biotrickling filter operated under counter- and co-current gas-liquid flow patterns. The best performance was found under counter-current conditions (maximum elimination capacity of 140 gS m(-3) h(-1)). Nevertheless, switching conditions between co- and counter-current flow lead to a favorable redistribution of biomass and elemental sulfur along the bed height.

Identification of enhanced hydrogen and ethanol Escherichia coli producer strains in a glycerol-based medium by screening in single-knock out mutant collections.

Background: Earth's climate is warming as a result of anthropogenic emissions of greenhouse gases from fossil fuel combustion. Bioenergy, which includes biodiesel, biohydrogen and bioethanol, has emerged as a sustainable alternative fuel source. For this reason, in recent years biodiesel production has become widespread but this industry currently generates a huge amount of glycerol as a by-product, which has become an environmental problem in its own right.

A systematic analysis of TCA Escherichia coli mutants reveals suitable genetic backgrounds for enhanced hydrogen and ethanol production using glycerol as main carbon source.

Biodiesel has emerged as an environmentally friendly alternative to fossil fuels; however, the low price of glycerol feed-stocks generated from the biodiesel industry has become a burden to this industry. A feasible alternative is the microbial biotransformation of waste glycerol to hydrogen and ethanol. Escherichia coli, a microorganism commonly used for metabolic engineering, is able to biotransform glycerol into these products.

Kinetic and stoichiometric characterization of anoxic sulfide oxidation by SO-NR mixed cultures from anoxic biotrickling filters.

Monitoring the biological activity in biotrickling filters is difficult since it implies estimating biomass concentration and its growth yield, which can hardly be measured in immobilized biomass systems. In this study, the characterization of a sulfide-oxidizing nitrate-reducing biomass obtained from an anoxic biotrickling filter was performed through the application of respirometric and titrimetric techniques. Previously, the biomass was maintained in a continuous stirred tank reactor under steady-state conditions resulting in a growth yield of 0.

Biogas biodesulfurization in an anoxic biotrickling filter packed with open-pore polyurethane foam.

Biogas biodesulfurization by an anoxic biotrickling filter packed with open pore polyurethane foam at the laboratory scale (packed volume 2.4L) has been studied. The biotrickling system was operated for 620 days with biogas supplied continuously and two nitrate feeding regimes were tested (manual and programmed).

Strategies for pH control in a biofilter packed with sugarcane bagasse for hydrogen sulfide removal.

The biological removal of hydrogen sulfide at low concentration (<120 ppmv) was studied in a laboratory-scale biofilter packed with sugarcane bagasse and inoculated with a sulfur-oxidizing bacterial consortium isolated from activated sludge from a wastewater treatment plant (WWTP). Inlet loads from 1.31 to 20.

Study of the role played by NfsA, NfsB nitroreductase and NemA flavin reductase from Escherichia coli in the conversion of ethyl 2-(2'-nitrophenoxy)acetate to 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIBOA), a benzohydroxamic acid with interesting biological properties.

Benzohydroxamic acids, such as 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIBOA), exhibit interesting herbicidal, fungicidal and bactericidal properties. Recently, the chemical synthesis of D-DIBOA has been simplified to only two steps. In a previous paper, we demonstrated that the second step could be replaced by a biotransformation using Escherichia coli to reduce the nitro group of the precursor, ethyl 2-(2'-nitrophenoxy)acetate and obtain D-DIBOA.

Biofiltration of reduced sulphur compounds and community analysis of sulphur-oxidizing bacteria.

The present work aims to use a two-stage biotrickling filters for simultaneous treatment of hydrogen sulphide (H(2)S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). The first biofilter was inoculated with Acidithiobacillus thiooxidans (BAT) and the second one with Thiobacillus thioparus (BTT). For separate feeds of reduced sulphur compounds (RSC), the elimination capacity (EC) order was DMDS>DMS>MM.