Red yeast is the product obtained from fermentation of coarse cereals by Monascus and has multiple applications. In this study, aiming to evaluate the feasibility and yield of producing Monascus pigments using the bulk starchy coarse cereals such as maize, potato, sweet potato, and glutinous rice as the fermentation substrate of Monascus purpureus to optimize the process parameters for solid-state fermentation of maize Monascus. Taking different coarse cereals as carbon sources, three supplementation gradients including 2%, 4%, and 6% were set to conduct liquid-state fermentation and determine the pigment values of Monascus. Using whole maize grains as the substrate for solid-state fermentation, single-factor experiments were employed to investigate the influences of inoculum volume, temperature, and fermentation time on the pigment values of Monascus, followed by orthogonal design for optimization of fermentation. The results revealed that, under liquid-state conditions, the optimal supplementation levels for maize, potato, and sweet-potato flours were 4%, whereas glutinous rice flour performed best at 2%. Maximum pigment values were attained after 7 days of fermentation for all the four carbon sources. Sweet-potato flour produced significantly lower pigment values than the other three substrates, while no significant differences in pigment values from fermentation were observed among maize, potato, and glutinous-rice groups. In solid-state fermentation of maize Monascus, the pigment values was influenced by the factors such as temperature, fermentation time, and inoculum volume, and the order of influence of the factors was as follows: inoculum volume > fermentation time > temperature. The optimum fermentation processes were 20% of inoculum volume, 30 °C, and 11 days, and the red-pigment value of the fermentation product yielded was 102.81 U/g. These findings demonstrated that glutinous rice, maize, potato, and sweet potato were effective substrates for Monascus fermentation to produce Monascus pigments. Overall, maize presented the best comprehensive benefits for Monascus product production.
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