Effects and Mechanism of Blue Light on Monascus in Liquid Fermentation.

The effect of light on Monascus and the underlying mechanism have received a great deal of interest for the industrial application of Monascus pigments. In this study, we have examined the effects of blue light on the culture morphology, mycelium growth, pigments, and citrinin yield of Monascus in liquid-state and oscillation fermentation, and explored the mechanism at a physiological level. It was found that blue light affected the colony morphology, the composition (chitin content), and permeability of the Monascus mycelium cell wall in static liquid culture, which indicates blue light benefits pigments secreting from aerial mycelium to culture medium. In liquid oscillation fermentation, the yields of Monascus pigments in fermentation broth (darkness 1741 U/g, blue light 2206 U/g) and mycelium (darkness 2442 U/g, blue light 1900 U/g) cultured under blue light and darkness are different. The total pigments produced per gram of Monascus mycelium under blue light was also higher (4663 U/g) than that in darkness (4352 U/g). However, the production of citrinin (88 μg/g) under blue light was evidently lower than that in darkness (150 μg/g). According to the degradation of citrinin caused by blue light and hydrogen peroxide, it can be concluded that blue light could degrade citrinin and inhibit the catalase activity of Monascus mycelium, subsequently suppressing the decomposition of hydrogen peroxide, which is the active species that degrades citrinin.

光对红曲霉的影响及其潜在机制在红曲霉色素的工业应用方面受到了极大关注。在本研究中，我们研究了蓝光对液态和振荡发酵中红曲霉的培养形态、菌丝体生长、色素和桔霉素产量的影响，并在生理水平上探索了其机制。研究发现，在静态液体培养中，蓝光影响红曲霉菌落形态、红曲霉菌丝体细胞壁的组成（几丁质含量）和通透性，这表明蓝光有利于气生菌丝体向培养基中分泌色素。在液体振荡发酵中，在蓝光和黑暗条件下培养的发酵液（黑暗条件下为1741 U/g，蓝光条件下为2206 U/g）和菌丝体（黑暗条件下为2442 U/g，蓝光条件下为1900 U/g）中红曲霉色素的产量不同。蓝光下每克红曲霉菌丝体产生的总色素（4663 U/g）也高于黑暗条件下（4352 U/g）。然而，蓝光下桔霉素的产量（88μg/g）明显低于黑暗条件下（150μg/g）。根据蓝光和过氧化氢导致的桔霉素降解情况，可以得出结论：蓝光能够降解桔霉素并抑制红曲霉菌丝体的过氧化氢酶活性，进而抑制过氧化氢的分解，而过氧化氢是降解桔霉素的活性物质。