Optimal selection of agricultural products to inhibit citrinin production during submerged culture of Monascus anka

Agricultural products exhibit a “buffering nature” during autoclaving and fermentation processes: i.e., the final pH of agricultural product medium after Monascus fermentation maintains a certain value. The protein content of agricultural products strongly affects the buffering capacity and an extremely low final pH, below 3, can be achieved by the selection of agricultural products with low protein content, such as rice meal and cornmeal. This low pH can be used to inhibit citrinin biosynthesis during Monascus fermentation. Thus, optimal selection of agricultural products with low protein content may provide a novel strategy to inhibit citrinin production in submerged culture of Monascus anka at a low initial pH for the production of Monascus pigments. pH values ranging from 2.6 to 3 can be maintained in Monascus fermentation using cornmeal/wheat starch (30:30 g/L) as substrate at initial pH 2.5, where the concentration of intracellular pigments reaches 45 AU at 470 nm while citrinin is undetectable by TLC analysis.