Optimizing Submerged Cultivation for the Production of Red Pigments by Monascus purpureus on Soybean Meals using Response Surface Methodology

Monascus purpureus is a filamentous fungus with ability to produce pigments with therapeutic properties. Red pigments are especially used as additives, antioxidants, preservatives and substitutions for nitrites in food technology. To decrease fermentation costs, agro-industrial wastes such as soybean meals have been used as substrates. In the current study, red pigment production by Monascus purpureus on soybean meals was optimized.

In this study, red Monascus pigment production by Monascus purpureus ATCC 16362 was carried out under submerged fermentation using soybean meals as nitrogen sources to replace yeast extracts. Central composite design was used to assess the optimum level of soybean meal replacement (0-100%), ZnSO4.7H2O concentration (0-0.02 g l-1) and thermal stress time of spore suspension at 70°C (50-90 s). Red Monascus pigment and biomass productions were assessed as dependent responses.

The maximum production of red Monascus pigment (4.54 AU ml-1) was achieved under conditions of soybean meal replacement of 79.72%, ZnSO4.7H2O concentration of 0-0.02 g l-1 and thermal stress time of spore suspension of 81.89 s. The average yield of red Monascus pigment, conversion factor of biomass in red pigment YP/X and cell productivity included 0.324 AU ml-1 day-1, 1.10 AU L g-1 and 0.292 g l-1 day-1, respectively. Results of the current study have demonstrated that combination of soybean meal and yeast extract as nitrogen source is beneficial for the production of red Monascus pigment by Monascus purpureus.