NITROGEN ENRICHMENT OF STRAW COMPOST ASSOCIATED WITH GROWTH OF PLEUROTUS MUSHROOM by A. SENGUPTA1, A. ROY CHOWDHURY2 AND S CHAUDHURI 3

Abstract

Pleurotus is one edible wood rotting fungus artificially cultivated in cereal straw for production of protein rich mushroom fruit bodies. Average protein content of straw-grown Pleurotus mushrooms range between 25-30% of dry weight. Protein yield from high C/N ratio cereal straw composted with Pleurotus does not equivalence with nitrogen content of unsupplemented straw on per unit weight basis. We present here evidence of diazotrophic nitrogen fixation during 50-day growth of Pleurotus citrinopileatus in rice straw compost timed with spawn run to fruit body production. P. citrinopileatus grown straw compost, simultaneous to loss in dry weight during 50-day incubation period showed incremental values of nitrogenase activity measured as acetylene reduction activity. There was a parallel increase in the population of nitrogen fixing bacteria as indicated by bacterial colony counts of composted straw in nitrogen-less specific nutrient medium. Pleuorotus, during its growth on straw breaks down hemicellulose, cellulose and lignin to liberate sugars that allow substantial growth of straw-associated nitrogen fixing bacteria in the moist, micro-aerophilic environment of the compost. Nitrogen fixed by the bacteria is utilized by the fungus to yield protein rich mycelium and fruit body in one of the most outstanding prokaryote-eukaryote bioconversion systems of nature.