Miriam Lorenzo

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.

Different proportions of laccase isoenzymes produced by submerged cultures of Trametes versicolor grown on lignocellulosic wastes.

The white-rot fungus Trametes versicolor grown in submerged culture produced two laccase isoenzymes, LacI and LacII. Addition of insoluble lignocellulosic materials into the culture medium increased the total laccase activity. The proportion of laccase isoenzymes also changed depending on the lignocellulosic material employed, with ratios of activity LacII/LacI from 0.9 (barley straw) to 4.4 (grape stalks). Besides, this proportion played an important role in the dye decolourisation.

Screening of supports and inducers for laccase production by Trametes versicolor in semi-solid-state conditions

Abstract The production of laccase by Trametes versicolor under semi-solid-state conditions has been studied. Several supports (polyurethane foam, wheat straw, barley straw, wood shavings and barley bran) have been tested in order to determine the most suitable for laccase production by the above-mentioned microorganism. Barley bran led to the highest activity levels, reaching maximum values of about 1200 U/l. In this stage of research, several factors affecting laccase production (veratryl alcohol, xylidine, fresh support and the initial C/N ratio) were investigated. Xylidine was shown to be the best inducer of laccase activity, attaining values of about 1700 U/l. Moreover, the addition of fresh support not only prolonged culture lifetime but also enhanced activity levels, reaching in all the cases values higher than 2000 U/l. In addition, the decolourisation of three structurally different dyes by cultures grown on the best operating conditions determined in the present study, was monitored in order to assess the degrading capability of the ligninolytic complex secreted by such cultures. The decolourisation of all the dyes tested was almost total (85–96%) after 6 days of incubation.

Enhanced ligninolytic enzyme production and degrading capability of Phanerochaete chrysosporium and Trametes versicolor

Ligninolytic enzyme production by the white-rot fungi Phanerochaete chrysosporium and Trametes versicolor precultivated with different insoluble lignocellulosic materials (grape seeds, barley bran and wood shavings) was investigated. Cultures of Phanerochaete chrysosporium precultivated with grape seeds and barley bran showed maximum lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) activities (1000 and 1232 U/l, respectively). Trametes versicolor precultivated with the same lignocellulosic residues showed the maximum laccase activity (around 250 U/l). For both fungi, the ligninolytic activities were about two-fold higher than those attained in the control cultures. In vitro decolorization of the polymeric dye Poly R-478 by the extracellular liquid obtained in the above-mentioned cultures was monitored in order to determine the respective capabilities of laccase, LiP and MnP. It is noteworthy that the degrading capability of LiP when P. chrysosporium was precultivated with barley bran gave a percentage of Poly R-478 decolorization of about 80% in 100 s, whereas control cultures showed a lower percentage, around 20%, after 2 min of the decolorization reaction.