| The large stroma of Shiraia bambusicola P. Hennigs, a fungus parasitizing branches of the bamboo of Brachystachyum Keng, has been used as a valuable traditional Chinese medicine. Hypocrellins are of excellent antibacterial, anti-inflammatory, antitumor, antiviral and analgesic activities. Hypocrellins may also be used in many fields, such as medicine, agriculture and food additives. At present, the fruit bodies of S. bambusicola are collected from the wild resources. The production of hyprocrellins is greatly influenced by climate and distribution. Thus, this greatly limits the research and production of hypocrellines. For the past few years, some progress had been made toward artificial culture of S. bambusicola, but the yield of hypocrellins did not meet the need of industrial production. In this paper, we mainly studied the regulation of the medium composition and light quality on the growth and hypocrellin A production of our newly isolated strain Shiraia sp. S8In this research, the liquid fermentation medium of Shiraia sp. S8 strain was screened and the carbon and nitrogen source were optimized. The optional medium for hypocrellin A production was made up of 20% potato, 2% soluble starch, 0.4% NaNO3, 0.3% KH2PO4, 0.075% MgSO4, 0.001% VB1. The submerged fermentation culture was performed in 150 mL Erlenmeyer flasks containing 50 mL of medium and incubated at 28°C for 8 days on a rotary shaker at 150 rpm. The maximum production of hypocrellin A 58.53 mg/L was observed which improved 1.71 times compared to the un-optimized medium.Secondly, we carried out research on the effect of different light quality on colony morphology and mycelial growth and development. We observed that colony surface covered with fluffy white aerial hyphae, no red pigment produced, the suppression of extending and branching hyphae and significantly increased the number of conidia when S8 strain exposed to blue light. No significant different phenomena were observed when compared with dark culture conditions. In dark, a small amount of aerial hyphae grew on the central of colony and red pigment covered almost the entire surface of the culture medium. The hyphae elongated and branched obviously under the microscopic observation. No significant change in the number of conidia was found under different light conditions excepted blue light.Then, we studied the effect of different light quality conditions on biomass and hypocrellin A production of S8 strain. We found that the biomass changed little in different conditions, red light could significantly stimulate pigment production but blue light could significantly suppressed pigment production. In addition, red light intensity could also affect the production of pigment. The best red light intensity was 200 lux and hypocrellin A production was 168.5 mg/L.Finally, oxidation-reduction status of S8 strain treated by red light was measured. As S8 strain was treated by red light, the content of H2O2 was 1.3 times higher than that cultured in the dark. Ascorbate peroxidase(APX), catalase(CAT) and superoxide dismutase(SOD) activities respectively reached a peak of 231.42, 39.46 and 79.90 U/mg protein after red light irradiated for 4 d and 1.98-, 2.44- and 9.03-fold increased over that of the dark group. These results indicated that red light could bring about ROS brust. Red light could also induce hypocrellin biosynthesis by up-regulating the expression level of genes(Mono, PKS, Omef and MFS) involved in hypocrellin synthesis.This study investigated the effect of the composition of medium and light quality on the growth and hypocrellin A production of S8 strain. By investigation of changes of morphology, growth status, redox situationin and hypocrellin synthesis related gene expression of S8 strain, we initially revealed the red light induced mechanism. These investigations are firstly applied in the research of S. bambusicola. A potential application in large-scale production of hypocrellin A is expected in future. |
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