Clean Monascus pigments production from Chinese rice wine wastes through submerged fermentation

Abstract

The potential for Monascus pigments (MPs) production in a mixture of Chinese rice wine lees, soaked rice wastewater and broken rice was explored. MPs production reached 120.1 U/mL with optimal solid-liquid ratio of culture medium 1:10 and 20 g/L broken rice addition at shake flask level. We further explored the effects of stirring speed on MPs production in 7.5 L agitated bioreactor. The stirring speed had a great impact on cell morphology and the maximum MPs concentration and yield were 128.4 U/mL and 8174 U/g respectively at 400 rpm. The soluble chemical oxygen demand for the soaked rice wastewater decreased by 78.7%, which was mainly due to the intake of carbohydrates, organic acids and amino acids. Furthermore, a simultaneous fermentation process and production system with two-stage stirring speed control strategy was further developed in the 50 L pilot scale, in which the MPs production reached 158.9 U/mL. Meanwhile, Chinese rice wine wastes were fully utilized without addition of organic solvents during the process and no generation of new waste. Our results showed that Monascus was capable of converting Chinese rice wine wastes into natural pigments by submerged fermentation, which could provide an economic and environmentally friendly approach to reduce the cost of wastes treatment as well as high-value utilization.