Effect of Extracellular Factors on Growth and Dimorphism of Rhizopus oryzae with Multiple Enzyme Synthesizing Ability

Abstract

Rhizopus oryzae PR7 MTCC 9642 was a dimorphic fungus that showed a regular 90 days cycle of filament (mycelium) to pellet (yeast) transformation through a distinct bottom dwelling intermediate state and the pellets never revert back to filamentous form. Apart from the normal cycle, high temperature (37°C and above) and extreme pH also induced the yeast formation. Among the ions tested, calcium and chloride ions were found to restore the filamentous morphology, even in extreme pH and temperature. Cysteine HCl also played noteworthy role in maintaining mycelial growth even at adverse condition. Immobilized spores showed the appearance of intermediate form instead of typical yeast form even at high temperature. The strain could produce a number of extracellular hydrolytic enzymes like cellulolytic, xylanolytic, pectinolytic and amylolytic enzymes. The pellet and mycelial forms were found to be a better producer of cellulaselignocellulase enzymes and amylolytic enzymes respectively, which might be correlated with their infectivity. Increase in inoculum size, agitation during cultivation, change in carbon and nitrogen source failed to induce mycelial growth in extreme conditions, which might be explained as irreversible change of configuration of protein responsible for mycelial development.

Mycelial pellet formation by edible ascomycete filamentous fungi, Neurospora intermedia

“…Of the various factors screened in this study, pH was the only one to significantly influence pellet formation. Factors such as calcium ions (Liu et al 2013 ), trace metals (Zhou et al 2000 ), agitation rate (Cui et al 1997 ) or carbon source (Karmakar et al 2012 ), which otherwise influence pellet formation showed no significant effects on N. intermedia . Previous studies have revealed that pH is an important factor for pellet formation in most filamentous fungi, but that different strains respond differently to the same pH value.…”

Production of Extracellular Isoamylase and Endoglucanase by Entrapped Spores of Rhizopus oryzae PR7

“…Hence, industry workers opt for a non-mycelial state. As the immobilized spores of the present strain showed the appearance of intermediate form instead of typical mycelial form even at high temperature [29], immobilizing the spores of R. oryzae PR7 might be an effective and convenient method for bulk production of isoamylase and endoglucanse in bioreactors also. Although, in the present strain alginate gel beads produced with 9 % (w/v) Na-alginate was found to be most suitable for the production of both the enzymes, but Cacl 2 and BaCl 2 was found to be most suitable for the production of endoglucanase and isoamylase respectively by the immobilized spores.…”