Involvement of an extracellular H2O2-dependent ligninolytic activity of the white rot fungus Pleurotus ostreatus in the decolorization of Remazol brilliant blue R

Abstract

During solid-state fermentation of wheat straw, a natural lignocellulosic substrate, the white rot fungus Pleurotus ostreatus produced an extracellular H 2 O 2-requiring Remazol brilliant blue R (RBBR)-decolorizing enzymatic activity along with manganese peroxidase, manganese-independent peroxidase, and phenol oxidase activities. The presence of RBBR was not essential for the production of RBBR-decolorizing enzymatic activity by P. ostreatus, because this activity was also produced in the absence of RBBR. This RBBR-decolorizing enzymatic activity in crude enzyme preparations of 14-and 20-day-old cultures exhibited an apparent K m for RBBR of 31 and 52 M, respectively. The RBBR-decolorizing enzyme activity was maximal in the pH range 3.5 to 4.0. This activity was independent of manganese, and veratryl alcohol had no influence on it. Manganese peroxidase of P. ostreatus did not decolorize RBBR. This H 2 O 2-dependent RBBR-decolorizing enzymatic activity behaved like an oxygenase possessing a catalytic metal center, perhaps heme, because it was inhibited by Na 2 S 2 O 5 , NaCN, NaN 3 , and depletion of dissolved oxygen. Na 2 S 2 O 5 brought an early end to the reaction without interfering with the initial reaction rate of RBBR oxygenase. The activity was also inhibited by cysteine. Concentrations of H 2 O 2 higher than 154 M were observed to be inhibitory as well. Decolorization of RBBR by P. ostreatus is an oxidative process.

Oxidative coupling during gut passage in marine deposit‐feeding invertebrates

“…RBBR decolorization assay-H 2 O 2 -dependent decolorization of certain dyes can indicate oxidoreductive enzyme activity; for example, RBBR has been used for peroxidases in fungi (Glenn and Gold 1983;Pasti and Crawford 1991;Vyas and Molitoris 1995). We tested small volumes of gut fluid for peroxidase-like activity by incubating a RBBR solution and activating it with H 2 O 2 .…”

The influence of extracellular H2O2 production on decolorization ability in fungi

“…The results revealed that low (less than 0.5 µM) and also high (over 2 µM) H 2 O 2 production decreased the decolorization capacity for both dyes tested. VYAS and MOLITORIS (1995) also demonstrated an inhibition effect of high concentrations of H 2 O 2 on decolorization of RBBR in P. ostreatus. Our results showed that fungi producing H 2 O 2 in the concentration range 1.0 -1.5 µM exhibited the highest decolorization capacity.…”

Enzymes in Plant Metabolism of PCBs and PAHs

“…-Decolorisation of RBBR was estimated in a medium using 0.005% of RBBR according to VYAS and MOLITORIS [6]. In parallel, it was also detected after 1-2 weeks of growth of plants on agar media containing 0.02% of RBBR.…”