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1.
World J Microbiol Biotechnol ; 40(2): 67, 2024 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-38197973

RESUMO

In mining industries, biomining (comprising biooxidation and bioleaching) is implemented to extract metals from specific ores and waste streams with less environmental effect and expense. Usually, micron-sized gold particles are held in a crystal lattice of iron sulfide minerals and expensively extracted using common approaches. Researchers and industries are interested in developing recent technology and biologically sustainable methods in both pretreatment and further extraction steps for extracting this valuable metal from ores. Diverse studies in biooxidation, as a conventional pretreatment, and biocyanidation, as a new proposed biotechnological method in the downstream gold extraction step, have addressed scientific and technological issues in the extraction of this metal. These two methods have become economically practical by merging high-throughput microbiological data, extraction and recovery process knowledge, and theory validation. However, there is still a gap in the implementation of both the pretreatment method and extraction method due to the consistency and their compatibility with operational recovery conditions. This review brings out the recent biooxidation and biocyanidation improvements, innovation, industry and academic research, and obstacles to gold extraction with a brief explanation to address the recent developments.


Assuntos
Biotecnologia , Ouro , Oxirredução , Clima , Sulfetos
2.
Environ Res ; 239(Pt 2): 117275, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37827363

RESUMO

The occurrence of antibiotic residues in diverse water sources has long been acknowledged as a potential health concern due to the emergence and spread of antibiotic-resistant bacteria and genes. However, there have been limited studies into the presence of antibiotic-metal complexes (AMCs) in real-time wastewater matrices, and their impact on wastewater microbial communities. The present work, in this regard, investigated the stability of Imipenem-metal complexes (Me = Mg (II), Ca (II), Fe (II), Cu (II), and Al (III)) with computational studies, stoichiometry with potentiometric measurements, and their antibacterial activity towards wastewater model microorganisms- Bacillus subtilis (B. subtilis) and Escherichia coli (E. Coli) by Colony Forming Unit (CFU) method. The lower energy of Imipenem-metal complexes than the parent antibiotic- Imipenem, during energy optimization using density functional (DFT) methods, revealed that metal interactions of Imipenem stabilize the drug by minimizing its energy. Further, CFU studies indicated that these complexes display higher antimicrobial activity than parent antibiotics. The electron delocalization over the entire chelated system (AMCs) reduces polarity and increases the lipophilicity of the complexes, thereby facilitating stronger interaction between AMCs and the bacterial cell membrane. Results indicate increased antibacterial activity of Imipenem-metal complexes for both E. coli and B. subtilis. The antibacterial activity, was however, more pronounced in B. subtilis, with >97% growth inhibition for metal complexes of Imipenem (at a Minimum Inhibitory Concentration of 20 nM or 6 ppb (i.e., MIC90)), for both the stoichiometric ratios (metal to ligand) ratios (M: L 1: 1 and 2: 1). All around, with increased stability and toxicity, AMCs are emerging as contaminants of concern and demand immediate attention to devise methods for their removal.


Assuntos
Complexos de Coordenação , Imipenem , Imipenem/toxicidade , Complexos de Coordenação/química , Complexos de Coordenação/metabolismo , Complexos de Coordenação/farmacologia , Águas Residuárias/toxicidade , Escherichia coli , Antibacterianos/toxicidade , Antibacterianos/química , Metais/química , Bactérias/metabolismo , Testes de Sensibilidade Microbiana
3.
Molecules ; 28(14)2023 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-37513409

RESUMO

Whey is a dairy residue generated during the production of cheese and yogurt. Whey contains mainly lactose and proteins, contributing to its high chemical oxygen demand (COD). Current environmental regulations request proper whey disposal to avoid environmental pollution. Whey components can be transformed by yeast into ethanol and biomolecules with aroma and flavor properties, for example, 2-phenyethanol (2PE), highly appreciated in the industry due to its organoleptic and biocidal properties. The present study aimed to valorize agri-food residues in 2PE by developing suitable bioprocess. Cheese whey was used as substrate source, whereas crab headshells, residual soy cake, and brewer's spent yeast (BSY) were used as renewable nitrogen sources for the yeasts Kluyveromyces marxianus and Debaryomyces hansenii. The BSYs promoted the growth of both yeasts and the production of 2PE in flask fermentation. The bioprocess scale-up to 2 L bioreactor allowed for obtaining a 2PE productivity of 0.04 g2PE/L·h, twofold better productivity results compared to the literature. The bioprocess can save a treatment unit because the whey COD decreased under the detection limit of the analytical method, which is lower than environmental requirements. In this way, the bioprocess prevents environmental contamination and contributes to the circular economy of the dairy industry.


Assuntos
Queijo , Kluyveromyces , Álcool Feniletílico , Fermentação , Álcool Feniletílico/metabolismo , Técnicas de Cocultura , Leveduras/metabolismo , Kluyveromyces/metabolismo , Proteínas do Soro do Leite/metabolismo , Soro do Leite/metabolismo , Lactose/metabolismo
4.
Environ Res ; 207: 112196, 2022 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-34634314

RESUMO

In the recent years, endocrine disrupting compounds (EDCs) has received increasing attention due to their significant toxic effects on human beings and wildlife by affecting their endocrine systems. As an important group of emerging pollutant, EDCs have been detected in various aquatic environments, including surface waters, groundwater, wastewater, runoff, and landfill leachates. Their removal from water resources has also been an emerging concern considering growing population as well as reducing access to fresh water resources. EDC removal from wastewaters is highly dependent on physicochemical properties of the given EDCs present in each wastewater types as well as various aquatic environments. Due to chemical, physical and physicochemical diversities in these parameters, variety of technologies consisting of physical, biological, electrochemical, and chemical processes have been developed for their removal. This review highlights that the effectiveness of EDC removal is highly dependent of selecting the appropriate technology; which decision is made upon a full wastewater chemical characterization. This review aims to provide a comprehensive perspective about all the current technologies used for EDCs removal from various aquatic matrices along with rising challenges such as the antimicrobial resistance gene transfer during EDC treatment.


Assuntos
Disruptores Endócrinos , Poluentes Químicos da Água , Disruptores Endócrinos/análise , Humanos , Tecnologia , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água/análise
5.
J Environ Manage ; 308: 114507, 2022 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-35124315

RESUMO

The treatment of acid mine drainage (AMD) is of paramount importance for environmental sustainability. A two-stage process involving AMD remediation and simultaneous lipid production represents a highly efficient approach with zero-waste generation. Alkaline (NaOH) treatment of AMD at pH 8.0, 10.0, and 12.0 had significantly reduced metal loads (copper (Cu), cobalt (Co), chromium (Cr), cadmium (Cd), nickel (Ni), and zinc (Zn)) compared to the acidic pH range (4.0 and 6.0). The concentration levels of sulfates (SO4 = 4520 mg/L), iron (Fe = 788 mg/L), aluminum (Al = 310 mg/L), and manganese (Mn = 19.4) were reduced to 2971 mg/L, 10.3 mg/L, 16.4 mg/L, and 1.3 mg/L, respectively at pH value 8.0. AMD with a pH value of 8.0 was later chosen as an ideal medium to favor the lipid accumulation by Chlorella vulgaris. Algal biomass was increasing to 5.5 g/L from 0.6 g/L of AMD-based medium within 15 days of cultivation. The FTIR and SEM-EDS studies revealed significant morphological changes in the microbial cell wall. The metals might positively impact lipid production in microalgae, where lipid yield achieved 0.18 g/g of glucose with lipid content of 0.35 g/g of biomass. The fatty acid profile presented 53.4% of saturated fatty acid content with a cetane value of 60.7. Thus, the efficiency of C. vulgaris was demonstrated with AMD treatment proving it to be a good candidate for bioenergy production.


Assuntos
Chlorella vulgaris , Metais Pesados , Poluentes Químicos da Água , Concentração de Íons de Hidrogênio , Lipídeos , Mineração , Poluentes Químicos da Água/análise
6.
Crit Rev Biotechnol ; 40(7): 930-950, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32693642

RESUMO

Whey is a liquid residue generated during the production of cheese and yogurt. It has a pH between 3.9 and 5.6, and a high chemical oxygen demand (COD), from 60 to 80 g/L. Whey contains lactose, proteins, and minerals. Globally, approximately 50% of the whey generated is untreated and is released directly into the environment, which represents an environmental risk. To overcome whey management problems, conventional thermo-physical valorization treatments have been explored, which are complex, costly and energy-intensive. As an alternative, whey fermentation processes employing bacteria, fungi and yeast are economical and promising methods. Among them, yeast fermentation creates value-added products such as antimicrobials, biofuels, aromas, flavors, and antioxidants with no need for previous conditioning of the whey, such as hydrolysis of the lactose, prior to whey biorefining. The biorefining concept applied to whey is discussed using chemical and biological transformation pathways, showing their pluses and minuses, such as technical drawbacks. The main challenges and solutions for the production of fusel alcohols, specifically for 2-phenylethanol, are also discussed in this review.


Assuntos
Antioxidantes , Aromatizantes , Odorantes , Soro do Leite , Leveduras/metabolismo , Biotecnologia , Fermentação
7.
Environ Sci Technol ; 54(4): 2054-2067, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31904944

RESUMO

It is a general understanding that unconventional oil is petroleum-extracted and processed into petroleum products using unconventional means. The recent growth in the United States shale oil production and the lack of refineries in Canada built for heavy crude processes have resulted in a significant increase in U.S imports of unconventional oil since 2018. This has increased the risk of incidents and catastrophic emergencies during the transportation of unconventional oils using transmission pipelines and train rails. A great deal of effort has been made to address the remediation of contaminated soil/sediment following the traditional oil spills. However, spill response and cleanup techniques (e.g., oil recuperation, soil-sediment-water treatments) showed slow and inefficient performance when it came to unconventional oil, bringing larger associated environmental impacts in need of investigation. To the best of our knowledge, there is no coherent review available on the biodegradability of unconventional oil, including Dilbit and Bakken oil. Hence, in view of the insufficient information and contrasting results obtained on the remediation of petroleum, this review is an attempt to fill the gap by presenting the collective understanding and critical analysis of the literature on bioremediation of products from the oil sand and shale (e.g., Dilbit and Bakken oil). This can help evaluate the different aspects of hydrocarbon biodegradation and identify the knowledge gaps in the literature.


Assuntos
Recuperação e Remediação Ambiental , Poluição por Petróleo , Petróleo , Biodegradação Ambiental , Canadá , Ecossistema , Óleos
8.
Crit Rev Biotechnol ; 39(6): 817-834, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31138023

RESUMO

Fumaric acid (FA), a metabolic intermediate, has been identified as an important carbohydrate derived platform chemical. Currently, it is commercially sourced from petrochemicals by chemical conversion. The shift to biochemical synthesis has become essential for sustainable development and for the transition to a biobased economy from a petroleum-based economy. The main limitation is that the concentrations of FA achieved during bioproduction are lower than that from a chemical process. Moreover, the high cost associated with bioproduction necessitates a higher yield to improve the feasibility of the process. To this effect, genetic modification of microorganism can be considered as an important tool to improve FA yield. This review discusses various genetic modifications strategies that have been studied in order to improve FA production. These strategies include the development of recombinant strains of Rhizopus oryzae, Escherichia coli, Saccharomyces cerevisiae, and Torulopsis glabrata as well as their mutants. The transformed strains were able to accumulate fumaric acid at a higher concentration than the corresponding wild strains but the fumaric acid titers obtained were lower than that reported with native fumaric acid producing R. oryzae strains. Moreover, one plausible adoption of gene editing tools, such as Agrobacterium-mediated transformation (AMT), CRISPR CAS-9 and RNA interference (RNAi) mediated knockout and silencing, have been proposed in order to improve fumaric acid yield. Additionally, the introduction of the glyoxylate pathway in R. oryzae to improve fumaric acid yield as well as the biosynthesis of fumarate esters have been proposed to improve the economic feasibility of the bioprocess. The adoption of some of these genetic engineering strategies may be essential to enable the development of a feasible bioproduction process.


Assuntos
Fumaratos/metabolismo , Engenharia Metabólica , Sistemas CRISPR-Cas , Escherichia coli/genética , Escherichia coli/metabolismo , Rhizopus/genética , Rhizopus/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo
9.
Ecotoxicol Environ Saf ; 172: 488-503, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30738231

RESUMO

Biological treatment of cyanotoxins has gained much importance in recent decades and holds a promise to work in coordination with various physicochemical treatments. In drinking water treatment plants (DWTPs), effective removal of cyanotoxins with reduced toxicity is a primary concern. Commonly used treatments, such as ozonation, chlorination or activated carbon, undergo significant changes in their operating conditions (mainly dosage) to counter the variation in different environmental parameters, such as pH, temperature, and high cyanotoxin concentration. Presence of metal ions, natural organic matter (NOM), and other chemicals demand higher dosage and hence affect the activation energy to efficiently break down the cyanotoxin molecule. Due to these higher dose requirements, the treatment leads to the formation of toxic metabolites at a concentration high enough to break the guideline values. Biological methods of cyanotoxin removal proceed via enzymatic pathway where the protein-encoding genes are often responsible for the compound breakdown into non-toxic metabolites. However, in contrast to the chemical treatment, the biological processes advance at a much slower kinetic rate, predominantly due to a longer onset period (high lag phase). In fact, more than 90% of the studies reported on the biological degradation of the cyanotoxins attribute the biodegradation to the bacterial suspension. This suspended growth limits the mass transfer kinetics due to the presence of metal ions, NOMs and, other oxidizable matter, which further prolongs the lag phase and makes biological process toxic-free, albeit less efficient. In this context, this review attempts to bring out the importance of the attached growth mechanism, in particular, the biofilm-based treatment approaches which can enhance the biodegradation rate.


Assuntos
Toxinas Bacterianas/isolamento & purificação , Água Potável/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água , Biodegradação Ambiental , Biofilmes , Reatores Biológicos , Cianobactérias/metabolismo , Monitoramento Ambiental , Microcistinas/isolamento & purificação
10.
J Environ Qual ; 47(2): 297-305, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29634787

RESUMO

A combination of processes was required for the proper treatment of old landfill leachate, as it contained a high concentration of pollutants. Humic substances comprised half of the total organic carbon in the raw leachate. Mobility of di(2-ethylhexyl) phthalate (DEHP) and metals could depend on the fate of these substances. Characterization of carbon in raw leachate and effluent of the membrane bioreactor, biofiltration, electro-oxidation, electro-coagulation, and nanofiltration showed complete removal of suspended solids and colloids. Physical processes could not remove the hydrophilic fraction due to its lower molecular weight. However, high removal of the hydrophilic fraction with a molecular weight <500 Da was expected in the biological process. In comparison with fulvic acid, larger sized humic acid resulted in complete removal by physicochemical processes. Because of DEHP partitioning on dissolved organic matter, especially on humic substances, its removal could be correlated with total organic carbon removal. Metals such as iron, aluminum, magnesium, and lead showed removal efficiency >80% in biological processes. Electro-deposition on the surface of an electrode and precipitation by hydroxide resulted in removal efficiencies >90 and >50% in electro-coagulation and electro-oxidation, respectively. Rejection of metals by nanofiltration was >80% and depended on the size and charge of cation. All in all, a combination of membrane bioreactor and nanofiltration seems to be the optimal process configuration for efficient treatment of old landfill leachate.


Assuntos
Substâncias Húmicas/análise , Eliminação de Resíduos , Poluentes Químicos da Água/análise , Reatores Biológicos , Ferro
11.
Water Environ Res ; 90(7): 604-614, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30188278

RESUMO

In the current study, sequential nitrification and anoxic experiments in synthetic municipal wastewater were exposed to 0.5 to 100 mg/L of chlortetracycline for 24 h to evaluate acute impact on the nitrification, and denitrification processes of biological treatment. Both processes were significantly (p < 0.05) inhibited at >50 mg/L of chlortetracycline, and the results revealed that nitrification was adversely affected by chlortetracycline compared with the anoxic process. In nitrification, chemical oxygen removal (COD) and ammonia oxidation kinetics were 50% inhibited at 10 mg chlortetracycline/L, and nitrite oxidation kinetics at 0.5 mg chlortetracycline/L. Likewise, in the anoxic process, 14 and 10 mg/L of chlortetracycline inhibited 50% of COD removal and nitrate reduction kinetics, respectively. In nitrification and denitrification, 90% of chlortetracycline was removed by adsorbing onto sludge suspended solids. In addition, a higher chlortetracycline concentration in anoxic effluent, compared with aerobic effluents, indicated a dissimilarity in the composition of sludge solids, pH, and biomass production for both processes.


Assuntos
Reatores Biológicos/microbiologia , Clortetraciclina/farmacologia , Desnitrificação/efeitos dos fármacos , Nitrificação/efeitos dos fármacos , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Amônia/metabolismo , Análise da Demanda Biológica de Oxigênio , Clortetraciclina/química , Concentração de Íons de Hidrogênio , Oxirredução , Eliminação de Resíduos Líquidos/instrumentação , Poluentes Químicos da Água/química , Poluentes Químicos da Água/farmacologia
12.
Crit Rev Food Sci Nutr ; 57(6): 1078-1088, 2017 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-26560460

RESUMO

Spices are parts of plants that due to their properties are used as colorants, preservatives, or medicine. The uses of spices have been known since long time, and the interest in the potential of spices is remarkable due to the chemical compounds contained in spices, such as phenylpropanoids, terpenes, flavonoids, and anthocyanins. Spices, such as cumin (cuminaldehyde), clove (eugenol), and cinnamon (cinnamaldehyde) among others, are known and studied for their antimicrobial and antioxidant properties due to their main chemical compounds. These spices have the potential to be used as preservatives in many foods namely in processed meat to replace chemical preservatives. Main chemical compounds in spices also confer other properties providing a variety of applications to spices, such as insecticidal, medicines, colorants, and natural flavoring. Spices provide beneficial effects, such as antioxidant activity levels that are comparable to regular chemical antioxidants used so they can be used as a natural alternative to synthetic preservatives. In this review, the main characteristics of spices will be described as well as their chemical properties, different applications of these spices, and the advantages and disadvantages of their use.


Assuntos
Especiarias/análise , Antocianinas/análise , Antocianinas/química , Anti-Infecciosos/análise , Anti-Infecciosos/química , Antioxidantes/análise , Antioxidantes/química , Cinnamomum zeylanicum/química , Cuminum/química , Flavonoides/análise , Flavonoides/química , Corantes de Alimentos/análise , Conservantes de Alimentos/análise , Conservantes de Alimentos/química , Zingiber officinale/química , Inseticidas/análise , Inseticidas/química , Piper nigrum/química , Extratos Vegetais/análise , Extratos Vegetais/química , Rosmarinus/química , Syzygium/química , Terpenos/análise , Terpenos/química
13.
Crit Rev Food Sci Nutr ; 57(13): 2775-2788, 2017 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-26462969

RESUMO

Coffee has been for decades the most commercialized food product and most widely consumed beverage in the world, with over 600 billion cups served per year. Before coffee cherries can be traded and processed into a final industrial product, they have to undergo postharvest processing on farms, which have a direct impact on the cost and quality of a coffee. Three different methods can be used for transforming the coffee cherries into beans, known as wet, dry, and semi-dry methods. In all these processing methods, a spontaneous fermentation is carried out in order to eliminate any mucilage still stuck to the beans and helps improve beverage flavor by microbial metabolites. The microorganisms responsible for the fermentation (e.g., yeasts and lactic acid bacteria) can play a number of roles, such as degradation of mucilage (pectinolytic activity), inhibition of mycotoxin-producing fungi growth, and production of flavor-active components. The use of starter cultures (mainly yeast strains) has emerged in recent years as a promising alternative to control the fermentation process and to promote quality development of coffee product. However, scarce information is still available about the effects of controlled starter cultures in coffee fermentation performance and bean quality, making it impossible to use this technology in actual field conditions. A broader knowledge about the ecology, biochemistry, and molecular biology could facilitate the understanding and application of starter cultures for coffee fermentation process. This review provides a comprehensive coverage of these issues, while pointing out new directions for exploiting starter cultures in coffee processing.


Assuntos
Café/química , Fermentação , Manipulação de Alimentos/métodos , Bebidas , Microbiologia de Alimentos , Fungos , Humanos , Paladar
14.
Biotechnol Appl Biochem ; 64(4): 496-508, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27277552

RESUMO

Lipase is one of the most widely used enzymes and plays an important role in biotechnological and industrial processes including food, paper, and oleochemical industries, as well as in pharmaceutical applications. However, its aqueous solubility and instability make its application relatively difficult and expensive. The immobilization technique is often used to improve lipase performance, and the strategy has turned out to be a promising method. Immobilized lipase on nanomaterials (NMs) has shown superiority to the free lipase, such as improved thermal and pH stability, longer stable time, and the capacity of being reused. However, immobilization of lipase on NMs also sometimes causes activity loss and protein loading is relatively lowered under some conditions. The overall performance of immobilized lipase on NMs is influenced by mechanisms of immobilization, type of NMs being used, and physicochemical features of the used NMs (such as particle size, aggregation behavior, NM dimension, and type of coupling/modifying agents being used). Based on the specific features of lipase and NMs, this review discusses the recent developments, some mechanisms, and influence of NMs on lipase immobilization and their activity. Multiple application potential of the immobilized lipases has also been considered.


Assuntos
Enzimas Imobilizadas/química , Lipase/química , Nanoestruturas/química , Enzimas Imobilizadas/metabolismo , Cinética , Lipase/metabolismo , Conformação Molecular
15.
Crit Rev Food Sci Nutr ; 56(13): 2133-48, 2016 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-25750989

RESUMO

Several food additives are added in food for their preservation to maintain the freshness of food (antioxidants) or to slow down or stop the growth of microorganisms (preservative agents). Nitrites and nitrates are used as preservative agents in meat. Nitrites give a smoked taste, a pinkish color in the meat and protect the consumers against the risk of bacterial deterioration. Their addition is however very limited as, in high dose, it can have risks on human health and the environment. Nitrites may also combine with secondary or tertiary amines to form N-nitroso derivatives. Certain N-nitroso compounds have been shown to produce cancers in a wide range of laboratory animals. Thus, alternatives of nitrates and nitrites are the object of numerous research studies. Alternatives, such as the addition of vitamins, fruits, chemicals products, natural products containing nitrite or spices, which have similar properties of nitrites, are in evaluation. In fact, spices are considered to have several organoleptic and anti-microbial properties which would be interesting to study. Several spices and combinations of spices are being progressively evaluated. This review discusses the sources of nitrites and nitrates, their use as additives in food products, their physicochemical properties, their negatives effects and the use of alternatives of nitrites and nitrates in preserving meat products.


Assuntos
Conservação de Alimentos/métodos , Conservantes de Alimentos , Produtos da Carne/análise , Nitratos , Nitritos , Animais , Antibacterianos , Fenômenos Químicos , Aditivos Alimentares , Humanos , Carne/análise , Nitratos/efeitos adversos , Nitratos/química , Nitratos/farmacocinética , Nitritos/efeitos adversos , Nitritos/química , Nitritos/farmacocinética , Nitrosaminas/química , Especiarias
16.
Int J Mol Sci ; 17(1)2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26771607

RESUMO

Anaerobic digestion using mixed-culture with broader choice of pretreatments for hydrogen (H2) production was investigated. Pretreatment of wastewater sludge by five methods, such as heat, acid, base, microwave and chloroform was conducted using crude glycerol (CG) as substrate. Results for heat treatment (100 °C for 15 min) showed the highest H2 production across the pretreatment methods with 15.18 ± 0.26 mmol/L of medium at 30 °C in absence of complex media and nutrient solution. The heat-pretreated inoculum eliminated H2 consuming bacteria and produced twice as much as H2 as compared to other pretreatment methods. The fermentation conditions, such as CG concentration (1.23 to 24 g/L), percentage of inoculum size (InS) (1.23% to 24% v/v) along with initial pH (2.98 to 8.02) was tested using central composite design (CCD) with H2 production as response parameter. The maximum H2 production of 29.43 ± 0.71 mmol/L obtained at optimum conditions of 20 g/L CG, 20% InS and pH 7. Symbiotic correlation of pH over CG and InS had a significant (p-value: 0.0011) contribution to H2 production. The mixed-culture possessed better natural acclimatization activity for degrading CG, at substrate inhibition concentration and provided efficient inoculum conditions in comparison to mono- and co-culture systems. The heat pretreatment step used across mixed-culture system is simple, cheap and industrially applicable in comparison to mono-/co-culture systems for H2 production.


Assuntos
Fermentação , Glicerol/metabolismo , Hidrogênio/metabolismo , Propilenoglicóis/metabolismo , Esgotos/química , Ácidos/química , Álcalis/química , Reatores Biológicos , Clorofórmio/química , Análise Fatorial , Glicerol/química , Temperatura Alta , Humanos , Hidrogênio/química , Concentração de Íons de Hidrogênio , Cinética , Micro-Ondas , Propilenoglicóis/química , Esgotos/microbiologia , Gerenciamento de Resíduos/métodos
17.
J Environ Manage ; 184(Pt 2): 318-326, 2016 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-27733297

RESUMO

Combination of high performance membrane bioreactor (MBR) equipped with ultrafiltration and electro-oxidation process (EOP) by boron-doped diamond electrode (BDD) was used to effectively treat highly contaminated old landfill leachate. MBR and EOP were optimized for raw and pretreated landfill leachate. Seasonal changes dramatically affected the both processes' performance, as the landfill leachate was ¾ more concentrated in winter. For MBR, organic load rate of 1.2 gCOD/L/day and sludge retention time of 80 days was considered as the optimum operating condition in which COD, TOC, NH4+ and phosphorous removal efficiencies reached the average of 63, 35, 98 and 52%, respectively. The best performance of EOP was in current intensity of 3 A with treatment of time of 120 min. Effluent of electro-oxidation was more toxic due to the presence of radicals and organochlorinated compounds. These compounds were removed by stripping or assimilation of sludge if EOP was used as a pretreatment method. Furthermore, the energy consumption of EOP was decreased from 22 to 16 KWh/m3 for biologically treated and raw landfill leachate, respectively.


Assuntos
Reatores Biológicos , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Boro , Diamante , Eletrodos , Desenho de Equipamento , Substâncias Húmicas , Oxirredução , Quebeque , Esgotos , Ultrafiltração , Poluentes Químicos da Água/metabolismo
18.
Bioprocess Biosyst Eng ; 38(6): 1097-102, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25575763

RESUMO

Owing to CO2-free emission, hydrogen is considered as a potential green alternative of fossil fuels. Water is the major emission of hydrogen combustion process and gravimetric energy density of hydrogen is nearly three times more than that of gasoline and diesel fuel. Biological hydrogen production, therefore, has commercial significance; especially, when it is produced from low-cost industrial waste-based feedstock. Light independent anaerobic fermentation is simple and mostly studied method of biohydrogen production. During hydrogen production by this method, a range of organic acid byproducts are produced. Accumulation of these byproducts is inhibitory for hydrogen production as it may result in process termination due to sharp decrease in medium pH or by possible metabolic shift. For the first time, therefore, a two-phase anaerobic bioreactor system has been reported for biohydrogen production which involves in situ extraction of different organic acids. Among different solvents, based on biocompatibility oleyl alcohol has been chosen as the organic phase of the two-phase system. An organic:aqueous phase ratio of 1:50 has been found to be optimum for hydrogen production. The strategy was capable of increasing the hydrogen production from 1.48 to 11.65 mmol/L-medium.


Assuntos
Ácidos/isolamento & purificação , Hidrogênio , Compostos Orgânicos/isolamento & purificação , Anaerobiose , Fermentação , Solventes/química
19.
J Environ Sci (China) ; 37: 37-50, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26574086

RESUMO

Highly hydrophobic Di 2-ethyl hexyl phthalate (DEHP) is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand (COD) and ammonia concentration were detected below 10 and 1.0mg/L, respectively for operating conditions of hydraulic retention time (HRT)=4 and 6hr, sludge retention time (SRT)=140day and sludge concentration between 11.5 and 15.8g volatile solid (VS)/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor, which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.


Assuntos
Reatores Biológicos , Cidades , Dietilexilftalato/isolamento & purificação , Dietilexilftalato/metabolismo , Imersão , Membranas Artificiais , Águas Residuárias/química , Animais , Incrustação Biológica , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos/microbiologia , Daphnia/efeitos dos fármacos , Dietilexilftalato/química , Dietilexilftalato/toxicidade , Nitrogênio/isolamento & purificação , Nitrogênio/metabolismo , Fósforo/isolamento & purificação , Fósforo/metabolismo , Solubilidade , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade
20.
J Biotechnol ; 389: 78-85, 2024 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-38718873

RESUMO

In a bid to explore the on-site biorefinery approach for conversion of forestry residues, lignocellulosic biomass into value-added products was studied. The bark white pine wood was subjected to the microwave technique of fast and slow hydrolysis under varying acid and biomass concentrations to produce levulinic acid (LA). The HCl (2% v/v) and plant biomass (1% w/v) were identified as the optimum conditions for fast wood hydrolysis (270 ºC for 12 sec), which led to maximum LA yield of 446.68 g/kgPB. The proposed sustainable approach is mild, quick, and utilized a very low concentration of the HCl for the production of LA. The hydrolysate was used as a medium for Kluyveromyces marxianus growth to produce 2-phenylethanol (2-PE). K. marxianus used 74-95% of furfural from hydrolysate as a co-substrate to grow. The proposed model of the integrated biorefinery is an affordable on-site approach of using forest waste into localized solutions to produce LA and 2-PE.


Assuntos
Biomassa , Ácidos Levulínicos , Álcool Feniletílico , Madeira , Ácidos Levulínicos/metabolismo , Madeira/química , Madeira/metabolismo , Hidrólise , Álcool Feniletílico/metabolismo , Kluyveromyces/metabolismo , Kluyveromyces/crescimento & desenvolvimento , Lignina/metabolismo , Lignina/química , Pinus/metabolismo , Pinus/química
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