M.T. Moreira

Simplified life cycle assessment of galician milk production

Milk, an example of staple food, has an outstanding demand by consumers as it is considered a prescription for good health. Life cycle assessment (LCA) is an excellent tool of environmental management and it provides a widespread knowledge on the environmental burdens associated to a product or to a human activity. In this study, a simplified methodology of LCA has been applied to analyse a representative scheme of milk production in Galicia (Spain), where a reliable inventory is still lacking. High quality data for the inventory was obtained in different representative fodder factories, farms and dairies for time periods over two years. The analysis of these data by LCA has permitted to quantify the potential impact associated to milk production and also to determine the reductions attained by the application of different improvement actions, such as the most adequate formulation of cattle feed and the implementation of treatment systems for water and air emissions. The consideration of these actions can lead to a maximum reduction of almost 22% of the global normalised impact.

Environmental and economic profile of six typologies of wastewater treatment plants.

The objective of wastewater treatment plants (WWTPs) is to prevent pollution. However, it is necessary to assess their sustainability in order to ensure that pollution is being removed, not displaced. In this research, the performance of 24 WWTPs has been evaluated using a streamlined Life Cycle Assessment (LCA) with Eutrophication Potential (EP) and Global Warming Potential (GWP) as environmental indicators, and operational costs as economic indicators. WWTPs were further classified in six typologies by their quality requirements according to their final discharge point or water reuse. Moreover, two different functional units (FU), one based on volume (m(3)) and the other on eutrophication reduction (kg PO(4)(3-) removed) were used to further determine sustainability. A correlation between legal requirements and technologies used to achieve them was found: Organic matter removal plants were found to be less costly both in environmental and economic terms if volume was used as the functional unit, while more demanding typologies such as reuse plants showed a trade-off between lower EP and higher cost and GWP; however, this is overcome if the second FU is used instead, proving the sustainability of these options and that this FU better reflects the objectives of a WWTP.

Evaluation of different fungal strains in the decolourisation of synthetic dyes

Of seven fungal strains tested for their ability to decolourise three structurally diverse synthetic dyes, Phanerochaete sordida, Bjerkandera sp. BOS55, Phlebia radiata, and Phanerochaete chrysosporium had average values of maximum decolourisation rates higher than 0.2 Δ[Absorbance] d−1. All seven fungi produced manganese peroxidase (MnP) but laccase activity was detected only in Phlebia radiata. No lignin peroxidase (LiP) activity was observed.

Oxidative Degradation of Azo Dyes by Manganese Peroxidase under Optimized Conditions

The application of enzyme‐based systems in waste treatment is unusual, given that many drawbacks are derived from their use, including low efficiency, high costs and easy deactivation of the enzyme. The goal of this study is the development of a degradation system based on the use of the ligninolytic enzyme manganese peroxidase (MnP) for the degradation of azo dyes. The experimental work also includes the optimization of the process, with the objective of determining the influence of specific physicochemical factors, such as organic acids, H2O2 addition, Mn2+ concentration, pH, temperature, enzyme activity and dye concentration. A nearly total decolorization was possible at very low reaction times (10 min) and at high dye concentration (up to 1500 mg L−1). A specific oxidation capacity as high as 10 mg dye degraded per unit of MnP consumed was attained for a decolorization higher than 90%. Among all, the main factor affecting process efficiency was the strategy of H2O2 addition. The continuous addition at a controlled flow permitted the progressive participation of H2O2 in the catalytic cycle through a suitable regeneration of the oxidized form of the enzyme, which enhanced both the extent and the rate of decolorization. It was also found that, in this particular case, the presence of a chelating organic acid (e.g., malonic) was not required for an effective operation. Probably, Mn3+ was chelated by the dye itself. The simplicity and high efficiency of the process open an interesting possibility of using of MnP for solving other environmental problems.

A packed-bed fungal bioreactor for the continuous decolourisation of azo-dyes (Orange II)

The degradation of an azo dye, Orange II, by immobilised Phanerochaete chrysosporium in a continuous packed bed bioreactor for periods longer than 30 days has been carried out. Nearly complete decolourisation (>95%) was achieved when working at a high dye load rate of 0.2 g x l(-1) x d(-1), a temperature of 37 degrees C, a hydraulic retention time (HRT) of 24 h and applying oxygen gas in a pulsed flow. These conditions allowed Manganese peroxidase (MnP) production and the subsequently Orange II decolourisation. A correlation between residual MnP activity in the effluent and decolourisation was established. Apparently, for decolourisation to be effective, a minimum MnP activity was required, no substantial increase in efficiency at MnP activities higher than 10 U x 1(-1) was observed. The treatment caused, the breakdown of the chromophoric group as well as the cleavage of the aromatic ring.

Combined cross-linked enzyme aggregates from versatile peroxidase and glucose oxidase: Production, partial characterization and application for the elimination of endocrine disruptors

Versatile peroxidase (VP) from Bjerkandera adusta was insolubilized in the form of cross-linked enzyme aggregates (CLEA®s). Of the initially applied activity 67% was recovered as CLEA®s. Co-aggregation of VP with glucose oxidase from Aspergillus niger led to an increased activity recovery of 89%. The combined CLEA®s showed higher stability against H(2)O(2) and exerted VP activity upon glucose addition. The elimination of the endocrine disrupting chemicals bisphenol A, nonylphenol, triclosan, 17α-ethinylestradiol and the hormone 17β-estradiol (10 mg L(-1) each) and the removal of their estrogenic activity by combined CLEA®s were tested in batch experiments. Within 10 min, the combined CLEA®s were able to remove all the endocrine disruptors except triclosan (residual concentration 74%). The removal of the estrogenic activity was higher than 55% for all compounds, except triclosan. A membrane reactor continuously operated with combined CLEA®s could almost completely remove bisphenol A (10 mg L(-1)) for 43 h.

DYE DECOLORIZATION BY MANGANESE PEROXIDASE IN AN ENZYMATIC MEMBRANE BIOREACTOR

In the present work an enzymatic membrane reactor (EMR) for the oxidation of azo dyes by manganese peroxidase (MnP) has been developed. The configuration consisted of a stirred tank reactor coupled with an ultrafiltration membrane. The membrane allowed for most of the enzymatic activity to be recovered while both the parent dye and the degradation products could pass through. Different operational strategies (batch, fed‐batch, and continuous) and parameters such as enzyme activity, H2O2 feeding rate, hydraulic retention time (in continuous operation), and dye loading rate were studied. At best conditions, a continuous operation with a dye decolorization higher than 85% and minimal enzymatic deactivation was feasible for 18 days, attaining an efficiency of 42.5 mg Orange II oxidized/MnP unit consumed.

Enzymatic membrane reactors for biodegradation of recalcitrant compounds. Application to dye decolourisation

Membrane bioreactors are being increasingly used in enzymatic catalysed transformations. However, the application of enzymatic-based treatment systems in the environmental field is rather unusual. The aim of this paper is to overview the application of enzymatic membrane reactors to wastewater treatment, more specifically to dye decolourisation. Firstly, the basic aspects such as different configurations of enzymatic reactors, advantages and disadvantages associated to their utilisation are revised as well as the application of this technology to wastewater treatment. Secondly, dye decolourisation by white-rot fungi and their oxidative enzymes are discussed, presenting an overall view from for in vivo and in vitro systems. Finally, dye decolourisation by manganese peroxidase in an enzymatic membrane reactor in continuous operation is presented.

Biodegradation of a polymeric dye in a pulsed bed bioreactor by immobilised Phanerochaete chrysosporium

An immobilised fungal bioreactor operated with pulsation of the gas-phase is proposed and operated at variable conditions for the continuous biological degradation of complex structures. In order to test the system, a hardly biodegradable dye (Poly R-478) was selected as a model compound and Phanerochaete chrysosporium as the ligninolytic fungus. High percentages of decolourisation--between 65% and 80%--under optimal conditions were achieved. Moreover, the system proved to have high stability with long operational periods (at least, 90 days). During the operation Manganese Peroxidase was the sole ligninolytic enzyme detected which points out this enzyme as the main substance responsible for decolourisation. The optimal conditions established were the following: temperature of 37 degrees C, use of oxygen, Mn2+ concentrations between 33 and 330 microM and exogenous H2O2 added in periodical pulses (as chemical reagent, 1 microM or as H2O2 enzymatically generated by 0.6 U L(-1) glucose oxidase and residual glucose).

Strategies for the continuous production of ligninolytic enzymes in fixed and fluidised bed bioreactors

Production of ligninolytic enzymes by white-rot fungi is a phenomenon typically associated to the secondary metabolism, the main drawback of which is the limited yield of the enzyme obtained under growth-limiting conditions and the morphological behaviour of these filamentous microorganisms while growing. An efficient production system is needed for the promising applications of these enzymes in bioprocesses such as detoxification of effluents and biobleaching of kraft pulp. Several bioreactor configurations were considered which were operated in batch or semi-continuous modes. These operational conditions permitted high titres of enzymatic activity, however, the extent of production was limited. A different modus operandi is then to be proposed to overcome these limitations. The present work reviews the state of production of ligninolytic enzymes and proposes a new method to achieve continuous production of manganese peroxidase (MnP). The method comprises a feeding policy based on controlled feed rates of nutrients and the use of an adequate bioreactor configuration. They were both key factors to attain and sustain continuous production of MnP. The feeding of limited concentrations of nutrients kept secondary metabolism in steady-state conditions and limited the fungal growth. The configuration of two conventional bioreactors (fluidised bed and fixed bed bioreactors) was modified with the introduction of pulsation of gas. Pulsation proved to be a good alternative to enhance nutrients and oxygen transfer as well as to maintain fungal cultures as independent bioparticles both for pellets and foam blocks of mycelia. Other environmental factors such as a Mn 2+ concentration of 5 mM and high oxygen tension enhanced MnP production. The hydraulics of the bioreactor also had effect on MnP production, the optimum corresponded to a plug flow model with partial mixing and an operating HRT of 24 h. This policy facilitated long operation periods, obtaining higher productivity rates than the best reported to date.