Evaluation of the roles of physical (osmotic, gamma irradiation and/or heat shock) stress factors on enzyme activities and protein accumulation in Pleurotus ostreatus mushroom and its descendent progenies.

摘要

Applications of agricultural and industrial wastes in the field of fermentation technology results in the production of many biomaterials as amino acids, enzymes, organic acids and proteins. The aim of this study was to increase the protein content of mushrooms grown on semisynthetic medium (APCEB substrate formulated from digested slaughter wastes, plant remains and KH₂PO₄salt) by application of physical stresses on spore and mycelial inocula. The inocula of Pleurotus ostreatus divisions representing three groups of spores and mature mycelia were gradually or abruptly stressed (one division was gamma irradiated, 0.0-3.0 kGy; the second was heat shocked, 25-50 degrees C and the third was osmotically stressed 0.00-150 mM NaCl). Different stressed inoclula were allowed to grow in liquid fermentation medium (APCEB), and at the end of the fermentation period different nitrogen and carbon fractions and enzyme activities were estimated in the fungal tissues. The result showed that combined heat shock and gradual gamma irradiation of the parent developing spores (PDS) and their progenies (GDS) produced significantly higher amount of tissue proteins (166.67, 170.88%) compared to parent mature spores (PMS) and their progenies (GMS)122.60 and 88.89%, respectively. The total amino acid content of GDS was significantly higher amount 132.77% compared with PDS, PMS and GMS (118.11, 120.20 and 84.36%, respectively). Also combined heat shock and gradual gamma irradiation resulted in the maximum increase in the activities of GOT, GPT, glutamate synthase (Gts) and glutamine synthetase (Gns) in parent developing spore (PDS) and their progenies (GDS), while glutamate dehydrogenase (G-H₂) activity was decreased. Electrophoretogram down regulated 47.0 kDa intense and 12 and 80 light protein bands/GMS. Heat shock resulted in an upregulation of light protein bands (120.0, 110.0, 96.0, 63.0 and 60.0)/GDS, PDS and PMS and down regulated intense 53.0 kDa and light 80.0, 19.0 protein bands/GMS. Heat shock and irradiation stresses had an accumulative effects. GDS spore inocula responded to physical stress (gradual gamma irradiation, 1.75 kGy and heat shock 35-40 degrees C) and produced the maximum percent control of protein and amino acids. The new acquired characters of the PDS were transferred to their progenies GDS while that of the parent mature spore PMS did not.