Lignocellulose degradation and ligninolytic enzymes activities of the white rot fungi Polyporus tenuiculus on poplar sawdust and wheat straw during solid estate fermentation.

OMARINI, A., ; GONZALEZ A.,; PISABARRO, G.,; RAMIREZ, L.

Reims

Simposio; Lignobiotech One: 1st Symposium on Biotechnology applied to lignocellulose; 2010

INRA-Universitity of Reims

Polyporus tenuiculus is a white rot fungus with an outstanding ability for degrading the components of different lignocellulose wastes. Little is known about the ligninolytic enzymes activities (Lacasse and Manganese peroxidase-MnP) and the modifications of the wheat straw and wood surface by this fungus at early stages of colonization at different temperatures. Solid state fermentation was performed using glass flasks containing 10 g of wheat straw or poplar sawdust (70 % humidity) which were inoculated with 10 ml of liquid medium containing P. tenuiculus. Flasks were incubated at different temperatures for different times. TAPPI methods (1998) were used to determine the lignin and hollocellulose loss of poplar sawdust and wheat straw substrates. Results obtained showed that: i) P. tenuiculus was able to reduce the lignin and hollocellulose content ii) the total extractives products obtained in both substrates during the time period of the experiment (eight weeks) were increased. The P. tenuiculus growth rate and its ability to decolour the Remazol Brilliant Blue R of dye were evaluated in agar plates at different temperatures (20, 25 and 30 ºC). Dye decoloured is associated with extracellular oxidative enzymes, principally laccase. Results obtained showed that P. tenuiculus increased its growth rate and its ability to degrade the dye when the temperature was increased. Ligninolytic enzymes activities were determined in both substrates incubated at different temperatures (20, 25 and 30 ºC) during 5, 12, 25, 30, 45 and 60 days. Laccase activity was measured by the oxidation of the 2,6-dimetoxyphenol (2,6-DMP). The reaction was carried out for 1 min before determining the variation in the absorbance at 468 nm. After the laccase value was recorded, MnSO4 (20 mM) was added and incubated for 1 more min before adding H2O2 30% (4 mM) solution. The reaction was allowed to proceed for 1 min more before and the absorbance was measured at 468 nm. The MnP activity was estimated as the difference between both activity measures. One unit of enzyme activity is defined as the formation of 1 μmol of product per min. The results obtained indicated that the laccase activity was higher in wheat straw extracts. MnP activity was principally found on poplar sawdust extracts. The mean laccase activity among the extracts obtained from wheat straw was 0,423 (S.D. 0,216) (U/ml) and for poplar sawdust 0,131 (S.D. 0,042) (U/ml). The MnP activity mean value was a 0,0249 (S.D. 0.0044) (U/ml). The results obtained indicate that P. tenuiculus could be an interesting species with potential use in the degradation of other lignocelloluses substrates such as those used for pulp and paper pretreatment and for biofuel industries.