Juan M Lema

University of Santiago de Compostela | USC · Department of Chemical Engineering

The study compares the potential to produce volatile fatty acids (VFA) from sewage sludge, both raw and thermally pre-treated in two modes of operation. In batch mode, raw sludge at pH 8 obtained the highest maximum VFA yield (0.41 g COD-VFA/g CODfed) whereas pre-treated sludge achieved a lower value (0.27 g COD-VFA/g CODfed). The operation of 5-L...

Coaggregation, a rare form of cell-cell interaction, characterized by the high specificity of recognition and adhesion of different bacterial species to each other has been identified as a key mechanism in multispecies biofilm formation in different environments. It is known that coaggregation is mediated by lectin–saccharide interactions between c...

The growing concern about antibiotic-resistant microorganisms has focused on the sludge from wastewater treatment plants (WWTPs) as a potential hotspot for their development and spread. To this end, it seems relevant to analyze the changes on the microbiota as a consequence of the antibiotics that wastewater may contain. This study aims at determin...

Organic micropollutants (OMPs) enter municipal wastewater treatment plants (WWTP) and tend to accumulate in sewage sludge, regardless of their sorption properties. Using sewage sludge as a soil fertilizer is a milestone within a circular economy view, although the presence of these OMPs entails potential risks that should be minimized, even if ther...

Fungal pretreatment of lignocellulosic biomass for bioethanol production is an environmental-friendly alternative to steam explosion. However, this biological pretreatment has been tested on a small scale, where most of the typical problems of solid-state fermentations (SSF), such as limited aeration or temperature control, are not observed. The ma...

This work investigates the impact of the sugar-to-protein (STP) ratio on the outcome of their anaerobic cofermentation in terms of substrate conversion and product selectivity. For this purpose, a continuous...

Biotransformation of trace-level organic micropollutants (OMPs) by complex microbial communities in wastewater treatment facilities is a key process for their detoxification and environmental impact reduction. Therefore, understanding the metabolic activities and mechanisms that contribute to their biotransformation is essential when developing app...

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is shed in the feces of infected people. As a consequence, genomic RNA of the virus can be detected in wastewater. Although the presence of viral RNA does not inform on the infectivity of the virus, this presence of genetic material raised the question of the effectiveness of treatmen...

This investigation studies the impact of trace elements supplementation on protein anaerobic conversion into volatile fatty acids (VFAs). Two continuous reactors were operated with two model substrates, casein and gelatin, at acid (pH 5) and neutral (pH 7) conditions, with the addition of macro and micronutrients. Micronutrients increased the acidi...

While heterotrophic microorganisms constitute the major fraction of activated sludge biomass, the role of heterotrophs in the biotransformation of organic micropollutants (OMPs) has not been fully elucidated. Yet, such knowledge is essential, particularly when conceiving novel wastewater treatment plants based on a two-stage process including an A-...

A methodology that programs eukaryotic or bacterial cells to encapsulate proteins of any kind inside micro/nanospheres formed by muNS-Mi viral protein was developed in our laboratory. In the present study such “in cellulo” encapsulation technology is utilized for immobilizing a protein with an enzymatic activity of industrial interest, CotA laccase...

Several studies have shown that organic micropollutants (OMPs) are biotransformed cometabolically in activated sludge systems. However, the individual role of heterotrophs in the microbial consortium is still not clear, i.e., there is still a gap regarding the influence of the heterotrophic activity on the cometabolic biotransformation kinetics and...

SARS-CoV-2 genetic material is detectable in the faeces of a considerable part of COVID-19 cases and hence, in municipal wastewater. This fact was confirmed early during the spread of the COVID-19 pandemic and prompted several studies that proposed monitoring its incidence by wastewater. This paper studies the fate of SARS-CoV-2 genetic material in...

Microorganisms extract energy from substrates following strategies that may seem suboptimal at first glance. Beyond the so-called yield-rate trade-off, resource allocation models, which focus on assigning different functional roles to the limited number of enzymes that a cell can support, offer a framework to interpret the inefficient substrate use...

The role of heterotrophic and nitrifying microorganisms in the (co-)metabolic biotransformation of 10 pharmaceutically active compounds (PhACs) was investigated. To this aim, biotransformation assays were performed with heterotrophic and nitrifying sludge developed separately in a two-stage full-scale activated sludge system. Each stage was operate...

https://rdcu.be/caWqx Among processes that control microbial community assembly, microbial invasion has received little attention until recently, especially in the field of anaerobic digestion. However, knowledge of the principles regulating the taxonomic and functional stability of microbial communities is key to truly develop better predictive mo...

This study investigates the influence of pH on protein conversion into volatile fatty acids by anaerobic mixed-culture fermentation, a topic that, in contrast to glucose fermentation, only had scarce and contradictory information available. Several experiments were performed with two model proteins (casein and gelatin) at three different pH values...

There is a growing interest in decentralized wastewater treatment systems, especially in regions with water scarcity problems or water management issues. This study aims to determine whether the perceived advantages and disadvantages (leading to acceptance) of decentralized wastewater plants in such regions are the same in regions where the populat...

The reindustrialization of acetone–butanol–ethanol (ABE) fermentation is hampered by its significant production cost, linked to high product inhibition and low product yield. ABE fermentation can be significantly enhanced by integrating in situ liquid–liquid extraction. In this study, hybrid simulations using Excel® and ASPEN Plus® were performed b...

Lactate production in anaerobic carbohydrate fermentations with mixed cultures of microorganisms is generally observed only in very specific conditions: the reactor should be run discontinuously and peptides and B vitamins must be present in the culture medium as lactic acid bacteria (LAB) are typically auxotrophic for amino acids. State‐of‐the‐art...

Mixed culture fermentation to produce volatile fatty acids stands as a solid option for valorising protein-rich wastes, such as those from the (agro)industry. However, the current knowledge about this process is limited and there are no appropriate tools for designing the production of volatile fatty acids from proteinaceous wastes. Available model...

This textbook summarizes the fundamentals of mass balance relevant for chemical engineers and an easy and comprehensive manner. Plenty of example calculations, schemes and flow diagrams facilitate the understanding. Case studies from relevant topics such as sustainable chemistry illustrate the theory behind current applications. (i) Mass balance f...

The valorisation of protein-rich residual streams by anaerobic mixed-culture fermentation (MCF) has been barely studied in contrast to carbohydrate-rich wastes. The aim of this work was, therefore, to investigate how protein composition, i.e. the amino acid (AA) profile, affects the individual consumption of amino acids and, consequently, the outco...

Sustainable development is driving a rapid focus shift in the wastewater and organic waste treatment sectors, from a “removal and disposal” approach towards the recovery and reuse of water, energy and materials (e.g. carbon or nutrients). Purple phototrophic bacteria (PPB) are receiving increasing attention due to their capability of growing photoh...

A bstract SARS-CoV-2 genetic material is detectable in the faeces of a considerable part of COVID-19 cases and hence, in the urban wastewater. This fact was confirmed early during the spread of the COVID-19 pandemic and prompted several studies that proposed monitoring its incidence by wastewater. This paper studies the fate of SARS-CoV-2 genetic m...

Novel wastewater treatment plants (WWTPs) are expected to be less energetically demanding than conventional ones. However, scarce information is available about the fate of organic micropollutants (OMPs) in these novel configurations. Therefore, the objective of this work is to assess the fate of OMPs in three novel WWTP configurations by using a p...

Full-text view-only version (free access): https://rdcu.be/2vLT. Although hospital wastewaters (HWWs) are usually discharged in urban sewage systems, their separate treatment has several benefits, such as the specific treatment of potential toxics as well as avoidance of further dilutions. In this work, an integrated industrial pilot plant (2200 L...

The increasing use of organic micropollutants (OMPs) and the lack of specific removal treatments lead to their presence in the environment. Mitigation strategies of OMPs in sewage treatment plants could be based on optimizing the removal capacity of already implemented technologies. For instance, anaerobic digestion processes are widely applied to...

Understanding the role of the different anaerobic digestion stages on the removal of organic micropollutants (OMPs) is essential to mitigate their release from wastewater treatment plants. This study assessed the fate of 21 OMPs during hydrolysis and acidogenesis to elucidate the contribution of these stages to the overall anaerobic removal. Moreov...

Anaerobic mixed-culture fermentations are interesting processes to valorise organic wastes by converting them to volatile fatty acids. One of the main issues is that certain operational conditions (e.g. pH or different substrate concentrations) can vary significantly the product spectrum. So far, there are no tools that take into the account the ch...

Novel wastewater treatment plants (WWTPs) are designed to be more energy efficient than conventional plants. One approach to becoming more energy efficient is the pre-concentration of organic carbon through chemically enhanced primary treatment (CEPT) or high-rate activated sludge (HRAS). This study compares these approaches in terms of energy dema...

Solvents with opposite characteristics in terms of biocompatibility towards Clostridium acetobutylicum and butanol extraction capacity: vegetable oils, 2-butyl-1-octanol and oleyl alcohol were tested in batch extractive fermentations. Concentration profiles of substrate, intermediate and final products were compared with a control (solvent-free) fe...

Proteinaceous organic wastes are suitable substrates to produce high added-value products in anaerobic mixed-culture fermentations. In these processes the stoichiometry of the biotransformations depends highly on operational conditions such as pH or feeding characteristics and there are still no tools that allow the process to be directed towards t...

Air-side stripping without a prior solid-liquid phase separation step is a feasible and promising process to control ammonia concentration in thermophilic digesters. During the process, part of the anaerobic biomass is exposed to high temperature, high pH and aerobic conditions. However, there are no studies assessing the effects of those harsh con...

Pretreatment technologies prior to anaerobic digestion (AD) have been developed with the aim of enhancing biogas productivity and reducing the presence of pathogens in digested sludge. Among them, thermal hydrolysis (TH) appears as the most promising one. In wastewater treatment plants (WWTPs) sludge is the end point of many organic micropollutants...

Sludge digesters of traditional WWTPs are commonly oversized and run at very conservative organic loading rates (OLR), so anaerobic co-digestion (AcoD) is a feasible technology to upgrade sludge digesters by increasing the methane productivity and the electrical self-production in WWTPs. In this study, a control strategy was applied to safely and o...

Leaf extracts of Eucalyptus globulus present a wide range of phenolic compounds with interest in the pharmaceutical , health, agricultural, cosmetic and food industries because of their medicinal properties. Although conventional solvent extraction is the most extensively used methodology to extract and isolate these active compounds, the excessive...

Rutin (quercetin-3-O-glycoside) has been demonstrated to possess beneficial properties for preventing various diseases. However, this compound shows poor solubility in water, thus implying scarce bioavailability, and low thermal stability [1]. The enzymatic polymerization of rutin has been proved as an efficient method for obtaining products with e...

Rutin (quercetin-3-O-glycoside) has been demonstrated to possess beneficial properties for preventing various diseases. However, this compound shows poor solubility in water, thus implying scarce bioavailability, and low thermal stability [1]. It has been proved that the enzymatic polymerization of rutin represents an efficient method for enhancing...

Novel wastewater treatment plants (WWTPs)are aimed to be more energetically efficient than conventional ones. Their first step is a chemical oxygen demand (COD)preconcentration stage with different alternatives, such as rotating belt filters (RBF), chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), or combinations ther...

There is still a lack of information about microbial interactions of anaerobic digestion microbiome during process disturbance which limits our ability to predict the mechanisms that drive community dynamics on these events. This paper aims to determine how an organic overloading affects these interactions and to characterize in detail the microbio...

Biotransformation of organic micropollutants (OMPs) in wastewater treatment plants ultimately depends on the enzymatic activities developed in each biological process. However, few research efforts have been made to clarify and identify the role of enzymes on the removal of OMPs, which is an essential knowledge to determine the biotransformation po...

Novel wastewater treatment plants (WWTPs), which are based on a partial nitritation-anammox (PN-anammox) process, enable higher chemical oxygen demand (COD) recovery to produce biogas and lower treatment costs. In this study, rotating belt filters (RBFs) were examined in different configurations to identify the opportunities for RBFs to be included...

Traditional wastewater treatment plants (WWTPs) are electrical consumers, with a usual high demand in the range of 0.3 to 0.6 kWh/m³ of wastewater treated. Their digesters are commonly oversized, and consequently operated at low organic loading rates (OLRs). This opens a great opportunity for anaerobic co-digestion (AcoD) as an interesting technolo...

The use of a hybrid membrane bioreactor (MBR) post-treatment system is proposed as a cost-efficient technology in order to minimize the environmental impact of anaerobic effluents, treating low-strength sewage at room temperature, such as their high nitrogen content and the presence of dissolved methane. In this research, nitrite was externally add...

Biotransformation of many organic micropollutants (OMPs) in sewage treatment plants is incomplete leading to their release into the environment. Recent findings suggest that thermodynamic aspects of the reaction as chemical equilibrium limit biotransformation, while kinetic parameters have a lower influence. Reversibility of enzymatic reactions mig...

Anaerobic mixed-culture fermentations are interesting processes to valorise organic wastes by converting them to volatile fatty acids. One of the main issues is that certain operational conditions (e.g. pH or different substrate concentrations) can vary significantly the product spectrum. So far, there are no tools that take into the account the ch...

Knowledge of connections between operational conditions, process stability, and microbial community dynamics is essential to enhance anaerobic digestion (AD) process efficiency and management. In this study, the detailed temporal effects of a sudden glycerol-based organic overloading on the AD microbial community and process imbalance were investig...

Acetone-butanol-ethanol (ABE) fermentation has a high potential for industrial application in lignocellulose-based biorefinery. Nevertheless, strong end-product inhibition is a severe limitation of this process, which can be partially solved by in situ product recovery techniques, such as extractive fermentation. In this work, the hydrolyzed cellul...

The enzymatic polymerization of rutin has been proved as an efficient method for obtaining products with enhanced properties, but in most cases, toxic solvents are needed to increase the initial substrate concentration. In this work, the possibility of producing rutin oligomers starting at a concentration beyond rutin aqueous solubility in a reacti...

A biological pretreatment of olive tree biomass (OTB) was carried out. First, seven white-rot fungi (WRF) were screened on solid-state fermentations by analyzing the substrate composition, ligninolytic enzymes production and enzymatic hydrolysis yields at three different pretreatment times (15, 30 and 45 days). Glucose released by enzymatic hydroly...

In this research, a new sequential batch reactor (SBR) coupled to an internal magnetic separator was developed. The separator consists of a set of axially magnetized permanent toroidal magnets, distributed along a non-magnetic steel rod, uniformly spaced with alternate polarity, which provide an external magnetic field of up to 1.2 T. The feasibili...

The fungal pretreatment of lignocellulosic biomass for the production of ethanol is a low-cost, safe, and environmentally friendly process that can be used as an alternative to the more energy-demanding physicochemical pretreatments. It is based on the special features of white-rot fungi (WRF), which have the ability to degrade lignin by using extr...

The enzyme-mediated polymerization of bioactive phenolic compounds, such as the flavonoid rutin, has gained interest due to the enhanced physico-chemical and biological properties of the products, which increases their potential application as a nutraceutical. In this work, the influence of enzyme activity on rutin oligomerization was evaluated in...

Municipal Solid Waste is mostly composed of organic material which is often treated in anaerobic reactors in waste treatment plants. In most cases, the obtained digestate undergoes a solid/liquid separation step, producing a liquid fraction (known as anaerobic supernatant) rich in ammonium nitrogen that has to be further treated in order to meet di...

Full-text view-only version (free access): https://rdcu.be/2vUm. Organic micropollutants (OMPs) comprise a wide group of substances highly consumed in modern societies. There has been a growing social and scientific interest on OMPs in wastewaters in the twentyfirst century. This research paper has identified the evolution of the research trends i...

The authors regret the absence of following information from the acknowledgements section, to comply with the EPSRC funding: “No new data were created during this study.” The authors would like to apologise for any inconvenience caused.

The main objective of this work was to assess the application of a modular system for the treatment of grey water in an office building with source separated sanitation in terms of disinfection and organic micropollutants (OMPs) abatement. The treatment line consists of an aerobic membrane bioreactor followed by a post-treatment unit (ozonation or...

En este trabajo se estudió la oligomerización enzimática de rutina empleando lacasa de Trametes versicolor, prestando especial atención a la influencia de la actividad enzimática inicial sobre los productos generados, un factor no estudiado previamente por otros autores. Para evitar el uso de compuestos tóxicos pero permitir el trabajo con concentr...

This article examines the potential benefits of using Data Envelopment Analysis (DEA) for conducting energy-efficiency assessment of wastewater treatment plants (WWTPs). WWTPs are characteristically heterogeneous (in size, technology, climate, function …) which limits the correct application of DEA. This paper proposes and describes the Robust Ener...

Anaerobic fermentation of organic wastes using microbial mixed cultures is a promising avenue to treat residues and obtain added-value products. However, the process has some important limitations that prevented so far any industrial application. One of the main issues is that we are not able to predict reliably the product spectrum (i.e. the stoic...

Biotransformation of most organic micropollutants (OMPs) during wastewater treatment is not complete and an unexplained steady decrease of the biotransformation rate with time is reported for many OMPs in different biological processes. To minimize and accurately predict the emission of OMPs into the environment, the mechanisms and limitations behi...

The application of livestock manure on agricultural land is being restricted due to its significant content of phosphorus (P) and nitrogen (N), leading to eutrophication. At the same time, the growing demand for N and P mineral fertilizers is increasing their production costs and causing the depletion of natural phosphate rock deposits. In the pres...

The textile and apparel industry is a solid and relevant industry in many developed or developing countries, mainly in Asia. In this region, the production and marketing of textiles are one of the primary sources of employment for millions of people and a major contributor to export earnings and gross domestic product

The development of nanotechnology has provided a range of diverse nanoscale carriers that can be potentially applied for enzyme immobilization. Among the different types of support, magnetic nanoparticles (mNPs) have received increasing attention because they can be easily recovered from the reaction medium by applying an external magnetic field. I...

BACKGROUND Organosolv pretreatment produces a hemicellulose‐rich stream with limited applications due to its toxicity. In this study, the beech wood organosolv liquor was valorized through the production of ligninolytic enzymes, the extraction of ganoderic acid, and the detoxification of this process stream. RESULTS Laccase and manganese peroxidas...

New technologies for wastewater treatment have been developed in the last years based on the combination of biological reactors operating under different redox conditions. Their efficiency in the removal of organic micropollutants (OMPs) has not been clearly assessed yet. This review paper is focussed on understanding the sorption and biotransforma...

The objective of this study was to evaluate the ability of one versatile peroxidase and the biocatalytically generated complex Mn(III)-malonate to polymerize coniferyl alcohol (CA) to obtain dehydrogenation polymers (DHPs) and to characterize how closely the structures of the formed DHPs resemble native lignin. Hydrogen peroxide was used as oxidant...

Although organosolv pretreatment allows extensive delignification of beech wood, the residual lignin present in the pulp may hinder the subsequent hydrolysis of the cellulose into fermentable sugars. With the purpose of increasing sugar production from cellulose hydrolysis, enzymatic and chemical oxidation stages were applied to the pulp previously...

Fractionation of lignocellulosic biomass with solvents (organosolv process) generates a hemicellulose-rich liquor with a high content of phenolics which is particularly toxic. This work addresses the utilization of this stream as a potential carbon source for the production of ligninolytic enzymes (LE). Among six basidiomycetes species, Irpex lacte...

Several studies showed that some organic micropollutants (OMPs) are biotransformed during anaerobic digestion (AD). Yet, most of them aim at reporting removal efficiencies instead of understanding the biotransformation process. Indeed, how each of the main AD stages (i.e., hydrolysis, acidogenesis, and methanogenesis) contribute to OMP biotransform...

The extraction of antioxidants from plant biomass is of high interest and it requires processing conditions that preserve the bioactivity of these compounds. The optimization of the solvent extraction of antioxidants from the leaves of Eucalyptus globulus is a key point for its exploitation at industrial scale. In this work, the Box-Behnken experim...

Anaerobic digestion of poultry manure is limited by the excessive levels of nitrogen and the high concentration of dry matter. These limitations are usually overcome either by applying procedures to remove nitrogen or by employing pretreatments that allows to solubilise organic matter. In this work, the treatment of poultry manure was enhanced by c...

The phototransformation of 18 organic micropollutants (OMPs) commonly detected in wastewater treatment plant (WWTP) effluents was examined attempting to explain their fate during UV disinfection in WWTPs. For this purpose, a lab-scale UV reactor (lamp emitting at 254nm) was used to study the influence of the operational conditions (UV dose, tempera...

Oxidative biocatalysis by laccase arises as a promising alternative in the development of advanced oxidation processes for the removal of xenobiotics. The aim of this work is to develop various types of nanobiocatalysts based on laccase immobilized on different superparamagnetic and non-magnetic nanoparticles to improve the stability of the biocata...

The enzymatic polymerization of phenolic compounds arouses increasing interest due to the production of derivatives with improved biological activity. The reaction yield, the molecular mass, the structure and the properties of synthesized polymers can be controlled by the reaction conditions such as solvent and type of enzyme and substrate. In this...