Setting the Foundations of Aqueous Three-Phase Systems (A3PS) in the Quest for a Rational Design

This work presents the first in-depth study of Aqueous Three-Phase Systems (A3PS) with the main purpose of unveiling their behaviour, hence contributing to the development of this new field. Thus, a complete definition of a quaternary system was carried through by describing all the regions in detail to represent them later on in a regular-tetrahedral diagram. The three aqueous faces of the tetrahedron demonstrated an undeviating influence in the segregation capacity. Furthermore, a method for comparing Aqueous Biphasis Systems (ABS) immiscibilities was set up in order to allow the evaluation and detection of the "limiting ABS" for the three-phase region. Finally, all this information was compiled and utilised to obtain a new strategy for an A3PS rational design, which can be applied with ABS libraries or in an experimental approach. In this sense, this strategy represents an undoubted advance towards future studies and development of A3PS, as this sequential application of the constructed knowledge is assumed to save time and resources.

Demonstrating the viability of halolipase production at a mechanically stirred tank biological reactor

The definition of halophiles as "the coming stars of industrial biotechnology" in a recent review demands new research efforts for their efficient production at bioreactor scale. In this sense, the scarcity of information about halolipases production has furthered the research on the viability of Halomonas sp. LM1C culture in a mechanically stirred bioreactor. The operating conditions have been optimized by means of a Central Composite Face-Centered (CCFC) design. The operation at low aerations (0.25 vvm) and moderate agitation rates (583 rpm) led to activity levels near 8000 U/L, which clearly surpasses the typical values detected for other extremophilic enzymes. The process at optimum conditions has been kinetically characterized and the oxygen volumetric mass transfer coefficient (K_La) has been determined.

Molecular dynamics studies on the structure and interactions of ionic liquids containing amino-acid anions

Several molecular dynamics (MD) simulations have been performed in order to obtain structural information on ionic liquids (ILs) based on amino-acid anions.

Unravelling the suitability of biological induction for halophilic lipase production by Halomonas sp. LM1C cultures

In this study, the viability of using biological induction as an alternative to the conventional chemical induction in lipase production by a novel halophilic microorganism, Halomonas sp. LM1C, has been demonstrated. Thus, a 9-times increase of lipase activity (3000U/L) was recorded when Staphylococcus equorum sp. AMC7 was present in the medium, which is competitive with the results obtained when Triton X-100 was added as chemical inducer. The GC-MS data allowed concluding the true nature of the biological inducer effect, as the existence of high percentages of isomeric forms of pentadecanoic acid were detected. The suitability of the proposed strategy was validated by operating at bench scale bioreactor, and the influence of bioreactor configuration on the biomass and lipolytic activity levels was studied. All the data were fitted to logistic and Luedeking & Piret models to characterize the bioprocess kinetics, concluding the growth-associated character of the produced lipolytic enzymes.

Scaling-up and ionic liquid-based extraction of pectinases from Aspergillus flavipes cultures

The viability of the scaling-up of pectinases production by Aspergillus flavipes at 5L-bioreactor scale has been demonstrated by keeping constant the power input, and a drastic increase in the endo- and exopectinolytic enzyme production was recorded (7- and 40-fold, respectively). The main process variables were modelled by means of logistic and Gompertz equations. In order to overcome the limitations of the conventional downstream strategies, a novel extraction strategy was proposed on the basis of the adequate salting-out potential of two biocompatible cholinium-based ionic liquids (N_1112OHCl and N_1112OHH₂PO₄) in aqueous solutions of Tergitol, reaching more than 90% of extraction.

Simultaneous biotreatment of Polycyclic Aromatic Hydrocarbons and dyes in a one-step bioreaction by an acclimated Pseudomonas strain

A Pseudomonas stutzeri strain acclimated to the presence of neoteric contaminants has been proposed for simultaneously remediating an effluent polluted with Polycyclic Aromatic Hydrocarbons and a diazo dye. The pollutants chemical nature imposed a strict control of both the medium composition and the operating conditions. pH, temperature and agitation rates of 7.0, 37.5 and 146 rpm, respectively, led to optimum levels of contaminant removal (higher than 60%) after RSM optimization. The validity of these conditions was checked at flask and bioreactor scale and the kinetics of the biotreatment was elucidated. The simulation of this one-step process applied at larger scale for the remediation of a 200,000 m(3)/year-effluent from a leather factory was compared with a conventional two-steps option. Great reductions in treatment times and in investment and manufacturing costs were concluded, proving the promising potential of the proposed process.

Ionic liquids for the concomitant use in extremophiles lysis and extremozymes extraction

Ionic liquids have been successfully proposed to modify membrane permeability in cultures of a model extremophilic bacterium Thermus thermophilus HB27, which makes up the first time that aqueous solutions of these molten salts are applied in downstream stages of this kind of microorganisms. The presence of 1g/L of C10MIMCl entails a great solubilisation of cell biomass, thus allowing the release of intracellular and membrane-bound enzyme. The influence on the enzyme activity of two inorganic salts such as Na2CO3 and (NH4)2SO4, selected on the basis of their high salting out potential and biocompatibility with enzymes, respectively, was investigated. In parallel, their ability to trigger phase segregation was confirmed in the presence of the enzyme crude, leading to very high levels of enzyme extraction (96%). The validity of the strategy was confirmed by operating at bioreactor scale, and the main bioprocess parameters were obtained by modelling the experimental data.

On the hunt for truly biocompatible ionic liquids for lipase-catalyzed reactions

One of the challenges in the field of biocatalysis is the search for efficient reaction media avoiding enzyme deactivation.

Hybrid sequential treatment of aromatic hydrocarbon-polluted effluents using non-ionic surfactants as solubilizers and extractants

A treatment train combining a biological and a physical approach was investigated for the first time in order to remediate polycyclic aromatic hydrocarbons (PAHs)-polluted effluents. Given the hydrophobic nature of these contaminants, the presence of non-ionic surfactants is compulsory to allow their bioavailability. The presence of these surfactants also entails an advantage in order to ease contaminant removal by the formation of aqueous two-phase systems (ATPS). The segregation ability of environmentally benign salts such as potassium tartrate, citrate, and oxalate was discussed for extracting phenanthrene (PHE), pyrene (PYR), and benzo[a]anthracene (BaA). The biological remediation efficiency reached circa 60% for PHE and PYR, and more than 80% for BaA. The coupling of ATPS subsequent stage by using potassium citrate allowed increasing the total PAH remediation yields higher than 97% of PAH removal. The viability of the proposed solution was investigated at industrial scale by using the software tool SuperPro Designer.

Pesticide removal from aqueous solutions by adding salting out agents

Phase segregation in aqueous biphasic systems (ABS) composed of four hydrophilic ionic liquids (ILs): 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium methylsulfate (C(n)C₁im C₁SO₄, n = 2 and 4), tributylmethyl phosphonium methylsulfate (P₄₄₄₁ C₁SO₄) and methylpyridinium methylsulfate (C₁Py C₁SO₄) and two high charge density potassium inorganic salts (K₂CO₃ and K₂HPO₄) were determined by the cloud point method at 298.15 K. The influence of the addition of the selected inorganic salts to aqueous mixtures of ILs was discussed in the light of the Hofmeister series and in terms of molar Gibbs free energy of hydration. The effect of the alkyl chain length of the cation on the methylsulfate-based ILs has been investigated. All the solubility data were satisfactorily correlated to several empirical equations. A pesticide (pentachlorophenol, PCP) extraction process based on the inorganic salt providing a greater salting out effect was tackled. The viability of the proposed process was analyzed in terms of partition coefficients and extraction efficiencies.

Novel physico-biological treatment for the remediation of textile dyes-containing industrial effluents

In this work, a novel remediation strategy consisting of a sequential biological and physical process is proposed to remove dyes from a textile polluted effluent. The decolorization ability of Anoxybacillus flavithermus in an aqueous effluent containing two representative textile finishing dyes (Reactive Black 5 and Acid Black 48, as di-azo and antraquinone class, respectively) was proved. The decolorization efficiency for a mixture of both dyes reached almost 60% in less than 12h, which points out the suitability of the selected microorganism. In a sequential stage, an aqueous biphasic system consisting of non-ionic surfactants and a potassium-based organic salt, acting as the salting out agent, was investigated. The phase segregation potential of the selected salts was evaluated in the light of different thermodynamic models, and remediation levels higher than 99% were reached.

Efficient PAHs biodegradation by a bacterial consortium at flask and bioreactor scale

In this work, the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) such as Phenanthrene (PHE), Pyrene (PYR) and Benzo[a]anthracene (BaA) has been investigated. A bacterial consortium consisting of two strains was used for the first time based on preliminary promising biodegradation data. They were tentatively identified as Staphylococcus warneri and Bacillus pumilus. Degradation values higher than 85% were obtained for each single PAH when operating at flask scale, whereas minimum levels of 90% of PAHs removal were obtained after just 3 days of cultivation at bioreactor scale. The operation in cometabolic conditions led to maximum levels about 75% and 100% at flask and bioreactor scale, respectively. All the experimental data were analyzed in the light of logistic and Luedeking and Piret type models, with the purpose to better characterize the biodegradation process by S. warneri and B. pumilus. Finally, the metabolic pathway followed to degrade each PAH was ascertained.

North Western Spain hot springs are a source of lipolytic enzyme-producing thermophilic microorganisms

Several hot springs in Galicia (North Western Spain) have been investigated as potential sources of lipolytic enzyme-producing thermophilic microorganisms. After isolating 12 esterase producing strains, 9 of them were assured to be true lipase producers, and consequently grown in submerged cultures, obtaining high extracellular activities by two of them. Furthermore, a preliminary partial characterization of the crude lipase, obtained by ultrafiltration of the cell-free culture supernatant, was carried out at several pH and temperature values. It is outstanding that several enzymes turned out to be multiextremozymes, since they had their optimum temperature and pH at typical values from thermoalkalophiles. The thermal stability in aqueous solution of the crude enzymes was also assayed, and the influence of some potential enzyme stabilizing compounds was tested. Finally, the viability of the selected microorganisms has been demonstrated at bioreactor scale.

Technoeconomic assessment of phenanthrene degradation by Pseudomonas stutzeri CECT 930 in a batch bioreactor

Polycyclic aromatic hydrocarbons (PAHs) are among the most persistent pollutants that accumulate in natural environment mainly as a result of anthropogenic activities. Therefore, the improvement of the available bank of microbial resources and information is crucial to the proper management of PAHs-polluted sites and effluents. In this work, Pseudomonas stutzeri CECT 930 was selected for aerobically degrading an aqueous effluent containing phenanthrene (PHE). Maximum PHE degradation of 90% was obtained both at flask and stirred tank bioreactor scale. All the experimental data were fitted to logistic and Luedeking and Piret models, and licensed to quantitatively ascertain a stronger dependence on the biomass of the metabolites triggering the bioremediation process. In addition, PHE degradation via protocatechuate pathway was elucidated through GC-MS data. Finally, based on the promising results of biodegradation, a preliminary economic evaluation of this process at industrial scale was approached by means of simulation data obtained with SuperPro Designer.

Assessment of a process to degrade metal working fluids using Pseudomonas stutzeri CECT 930 and indigenous microbial consortia

The development of a novel biological process to treat metal working fluids (MWFs)-containing effluents at bioreactor scale was pursued in this work. The bacteria Pseudomonas stutzeri CECT 930 was investigated for the first time as an alternative agent for MWF degradation. An adequate medium design and mixing and aeration system, as well as an appropriate microorganism proved to be crucial for reaching high levels of degradation by P. stutzeri and by an indigenous consortium (about 70% and 50% of reduction in total petroleum hydrocarbon content in less than 2 wk, respectively). Additionally, as there is no information in literature trying to kinetically characterize an MWF-polluted effluent degradation process, all the experimental data were fitted to logistic and Luedeking and Piret models, that allowed to elucidate the growth-associated character of the biodegradation process.

Decolorization of dye Reactive Black 5 by newly isolated thermophilic microorganisms from geothermal sites in Galicia (Spain)

In this study, thermophilic microbial strains from thermal spots in northwestern Spain displaying excellent decolorization capability were isolated. The research work tackled: (i) the ability of consortia to degrade a model di-azo dye Reactive Black at different pHs in flask cultures, obtaining that just neutral pHs licensed degradation levels near to 70%, (ii) the isolation of tree of the bacteria, which rendered possible reaching high levels of decolorization (80%) after just 24 h in aerobic conditions, and which were identified through 16S rRNA sequencing to possess high homology (99%) with Anoxybacillus pushchinoensis, Anoxybacillus kamchatkensis and Anoxybacillus flavithermus, and (iii) the cultivation of the isolates in a bench-scale bioreactor, which led to a decolorization rate two-fold higher than that obtained in flask cultures. Therefore, this work makes up the first time that a decolorization process of an azo dye by thermophilic microorganisms in aerobic conditions is investigated.

Strategies for improving extracellular lipolytic enzyme production by Thermus thermophilus HB27

In Thermus thermophilus HB27 cultures the localisation of lipolytic activity is extracellular, intracellular and membrane bound, with low percentage for the former. Therefore, the extracellular secretion must be increased in order to simplify the downstream process and to reduce the economic cost. This study focuses on the design of an innovative operational strategy to increase extracellular lipolytic enzyme production by T. thermophilus HB27 at bioreactor scale. In order to favour its secretion, the effect of several operational variables was evaluated. Among them, the presence of oils in the culture medium leads to improvements in growth and lipolytic enzyme activity. Sunflower oil is the most efficient inducer showing better results when added after 10h of growth. On the other hand, although surfactants lead to an almost complete inhibition of growth and lipolytic enzyme production, their addition along the culture could affect the location of the enzyme. Thus, by addition of surfactants at the stationary phase, a release of intracellular and membrane enzyme which increases the extracellular enzyme proportion is detected. Based on these results, strategies with successive addition of oil and surfactant in several culture phases in shake flask are developed and verified in a laboratory scale stirred tank bioreactor.

Production of a thermostable extracellular lipase by Kluyveromyces marxianus

Kluyveromyces marxianus was grown in submerged culture in a complex medium with several potential inducers of lipolytic activity (triacylglycerols, fatty acids). The highest extracellular lipolytic enzyme production (about 80 U ml(-1) in 3 d) was obtained when the medium was supplemented with 2 g urea l(-1) plus 5 g tributyrin l(-1). Addition of surfactants (1 g l(-1)) did not improve production. The lipase had a high thermal stability in aqueous solution (73% residual activity after 9 d at 50 degrees C, 16 min half-life time at 100 degrees C). It was also stable at acidic pH and showed good tolerance to organic solvents (70% residual activity after 2 d in n-hexane of cyclohexane).