S. Rodríguez Couto

Improving laccase production by employing different lignocellulosic wastes in submerged cultures of Trametes versicolor.

Laccase production by the white-rot fungus Trametes versicolor (CBS100.29) grown in submerged cultures was studied. Addition of different insoluble lignocellulosic materials into the culture medium in order to enhance laccase production was investigated. The lignocellulosic materials were grape seeds, grape stalks and barley bran, selected because of their availability and low cost, since they are agro-industrial wastes abundant in most countries. Barley bran gave the highest activities, a maximum value of 639U/l, which was 10 times the value attained in the cultures without lignocellulosics addition. The decolourisation of a model dye, Phenol Red, by the ligninolytic fluids obtained in the above-mentioned cultures was investigated. Grape stalk and barley bran cultures showed the highest ability to decolourise the dye, attaining a percentage of decolourisation of around 60% in 72 h.

Study of the degradation of dyes by MnP of Phanerochaete chrysosporium produced in a fixed-bed bioreactor.

The production of ligninolytic enzymes by the fungus Phanerochaete chrysosporium in a fixed-bed tubular bioreactor, filled with cubes of nylon sponge, operating in semi-solid-state conditions, was studied. Maximum individual manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of 1293 and 225 U/l were detected. The in vitro decolourisation of two structurally different dyes (Poly R-478, crystal violet) by the extracellular liquid obtained in the above-mentioned bioreactor was monitored in order to determine its degrading capability. The concentration of some compounds (sodium malonate, manganese sulphate) from the reaction mixture was optimised in order to maximise the decolourisation levels. A percentage of Poly R-478 decolourisation of 24% after 15 min of dye incubation was achieved. On the other hand, a methodology for a long treatment of these dyes based on the continuous addition of MnP enzyme and H(2)O(2) was developed. Moreover, this enzymatic treatment was compared with a photochemical decolourisation process. The former allowed to maintain the degradation rate almost constant for a long time, resulting in a decolourisation percentage of 70% and 30% for crystal violet and Poly R-478, respectively, after 2 h of treatment. As for the latter, it was not able to degrade Poly R-478, whereas crystal violet reached a degradation of 40% in 2 h.

Investigation of several bioreactor configurations for laccase production by Trametes versicolor operating in solid-state conditions

Abstract In the present paper, the production of laccase by Trametes versicolor (CBS 100.29) in laboratory-scale bioreactors, operating in semi-solid-state conditions, was studied. Three bioreactor configurations were investigated in order to determine the most suitable one for laccase production: immersion, expanded-bed and tray. In addition, the nature of support employed (inert or non-inert) on laccase production was also evaluated. According to the results attained in the previous work by our research group, nylon sponge and barley bran was employed as an inert and as a lignocellulosic support, respectively. Higher laccase activities were produced operating with barley bran than with nylon sponge as a support in all the configurations tested. As regards bioreactor design, the tray configuration led to the highest laccase activities especially operating with barley bran as a support, where activities of about 10-fold higher than that found in the corresponding cultivation with nylon sponge were attained. Therefore, it could be asserted that the tray bioreactor is a very appropriate bioreactor configuration to produce laccase by T. versicolor in solid-state conditions operating with lignocellulosic supports.

Photocatalytic degradation of dyes in aqueous solution operating in a fluidised bed reactor

This work reports a preliminary design of a new photochemical reactor and its application to photochemical degradation of two dyes, Crystal Violet and Azure B, operating in both batch and continuous processes. A novel kind of photocatalyst, consisting of ZnO immobilised in alginate gel beads, which is able to photodegrade organic dyes effectively, has been employed in the present study. When this photocatalyst, at a concentration of 1 g of ZnO per litre of alginate gel at 3%, was employed in batch process, almost total decolourisation of Crystal Violet in reaction times lower than 120 min was observed. Operating in continuous process at different residence times, it was possible to achieve a total decolourisation of both Crystal Violet and Azure B. Moreover, the total organic carbon content (TOC) was reduced to 90% in the former and to 52% in the latter. These results indicated that the photoreactor developed in the present work was able to degrade effectively dyes of different structures, revealing the non-specificity of the system.

Laccase activity from the fungus Trametes hirsuta using an air-lift bioreactor

Aim:  To produce high laccase activities from the white‐rot fungus Trametes hirsuta in an in‐house air‐lift bioreactor (ALB).

Ligninolytic enzyme production and the ability of decolourisation of Poly R-478 in packed-bed bioreactors by Phanerochaete chrysosporium

Abstract  The production of ligninolytic enzymes by the fungus Phanerochaetechrysosporium BKM-F-1767 (ATCC 24725) in packed-bed tubular bioreactors, operating in semi-solid-state conditions, was studied. Three types of carriers were assayed: cubes of polyurethane foam, cubes of nylon sponge and chopped corncob, in order to determine the more suitable one to produce ligninolytic enzymes by this fungus. The cultivations were carried out in discontinuous and in continuous mode.For discontinuous cultivation, maximum individual manganese-dependent peroxidase (MnP) activities of 1593, 1371 and 346 U/l were achieved in the bioreactors filled with cubes of nylon sponge, cubes of polyurethane foam and with corncob, respectively. On the other hand, lignin peroxidase (LiP) activities about 100 U/l were found in the two former and around 200 U/l in the latter. Moreover, laccase, was detected in all cultures, with average values of 30 U/l. Nonetheless, continuous mode cultivation led to lower ligninolytic enzyme activities than those produced in discontinuous, except in the case of the corncob.Furthermore, the decolourisation of the dye Poly R-478 by the above-mentioned cultures was investigated. The percentage of biological decolourisation reached was about 70% in the bioreactor filled with cubes of nylon sponge whereas it was rather low in the others (around 30%).

Utilisation of lignocellulosic wastes for lignin peroxidase production by semi-solid-state cultures of Phanerochaete chrysosporium.

In the present work, the production of ligninolytic enzymes by semi-solid-statecultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725),employing different lignocellulosic wastes as support, was investigated. Thewaste materials employed were grape seeds, wheat straw and wood shavings.Maximum lignin peroxidase activities of 1620 ± 123 U/l, 364 ± 35 U/l and 571 ± 42 U/l were attained, respectively. Nevertheless, lowmanganese-dependent peroxidase activities were found, being insignificantin the grape seed cultures. Moreover, the in vivo decolourisation of a model dye compound, the polymeric dye Poly R-478 (polyvinylamine sulfonateanthrapyridone), by the above-mentioned cultures was monitored to assessthe degrading capability of the extracellular liquid secreted by such cultures.The percentage of biological decolourisation attained by grape seed and woodshaving cultures was around 74% and 63%, respectively, whereas it was ratherlow (40%) in the wheat straw ones.

Stimulation of ligninolytic enzyme production and the ability to decolourise Poly R-478 in semi-solid-state cultures of Phanerochaete chrysosporium

Abstract The effect of adding some activators of ligninolytic enzyme production, Tween 80, veratryl alcohol and manganese (IV) oxide, to semi-solid-state cultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725) was studied. As carrier, cubes of polyurethane foam were employed. Supplementing the cultures with Tween 80, a maximum manganese-dependent peroxidase (MnP) activity of 350 U/l was achieved. This value was about 3-fold higher than that obtained in the control cultures (without Tween 80). When not only Tween 80 but also veratryl alcohol or manganese (IV) oxide were incorporated into the culture medium, the effect was greater and led to MnP activities of about 600 and 1100 U/l with alcohol or oxide, respectively. These activities were notably higher than those obtained in the control cultures (about 3-fold and 7-fold, respectively). The decolourisation of the dye Poly R-478 by the above-mentioned cultures was investigated. The percentage of biological decolourisation reached at the end of all the cultivations was higher than 95%.

Production of manganese-dependent peroxidase in a new solid-state bioreactor by Phanerochœte chrysosporium grown on wood shavings. Application to the decolorization of synthetic dyes

The production of manganese-dependent peroxidase (MnP) byPhanerochœte chrysosporium in a new solid-state bioreactor, the immersion bioreactor, operating with lignocellulosic waste, such as wood shavings, was investigated. Maximum MnP and lignin peroxidase (LiP) activity of 13.4 and 8.48 μkat/L were obtained, respectively. Thein vitro decolorization of several synthetic dyes by the extracellular liquid produced in the above-mentioned bioreactor (containing mainly MnP) was carried out and its degrading ability was assessed. The highest decolorization was reached with Indigo Carmine (98%) followed by Bromophenol Blue (56%) and Methyl Orange (36%), whereas Gentian Violet was hardly decolorized (6%).

Laccase from Trametes hirsuta Grown on Paper Cuttings: Application to Synthetic Dye Decolorization at Different pH Values

The potential of paper cuttings to produce laccase from Trametes hirsuta grown under solid‐state conditions was investigated. In addition, cultures were also grown on barley bran, a support commonly used in solid‐state fermentation (SSF), for comparison. Paper cutting cultures showed a maximum individual laccase activity of 7695 U/L on day 9. In addition, the ability to decolorize two structurally different dyes (Indigo Carmine and Lissamine Green B) by the extracellular liquid from both paper and barley bran cultures at pH values between 2 and 11 was analyzed. Laccase‐containing enzyme preparations from both cultures decolorized the dyes tested at pH values between 4 and 7 and, in addition, the laccase‐containing enzyme preparation from paper cutting cultures was also able to decolorize the dyes tested at alkaline pH values. This is a very interesting and novel result, since no decolorization by fungal laccases has been reported until recently at pH values higher than pH 7.