Effect of stress on growth, pigment production and morphology of Monascus sp. in solid cultures

The aim of the current work was to study the influence of stress on pigment production in Monascus purpureus under solid-state fermentation. Thermal stress was induced by incubating the culture at various high temperatures. For giving osmotic stress, different concentration of NaCl and glycerol were added to the solid substrate prior to autoclaving. Morphological studies were done by light microscopy and scanning electron microscopy. When the cells were exposed to high temperature, high glycerol and salt concentration, significant changes in pigment production and growth were observed. High temperature (>45 degrees C) induced the production of more yellow pigments. High concentration of NaCl induced conidiation and caused a decrease in fungal biomass (up to 50%) but red pigment production increased from 11.86 OD/gds to 20.14 OD/gds. When subjected to glycerol stress, a significant increase in aerial mycelia was observed when compared with the control conditions. The results attain significance for exploiting the fungal culture of Monascus purpureus LPB 97 for producing colors of choice--red, or yellow, or increasing the yield of red pigments considerably. Thus, these results could well impact the commercial aspect of Monascus pigments for industrial application.