Effect Of Oxidative Stress And Selenium On Sclerotial Differentiation And Antioxidant Properties Of Penicillium Thomii

The sclerotial differentiation and carotenoid metabolism of Penicillium thomii PT95 and Q1 strains those isolated from mixed forest soil from Fenyang and pine rhizosphere from Wutai in Shanxi had be studied in our laboratory. On the basic of preliminary work, the aim of this work was to study the effect of oxidative stress and selenium on sclerotial differentiation, sclerotial biomass, carotenoids content, ascorbic acid content, selenium content and antioxidative properties in sclerotium of PT95 and Q1 strains under different conditions of oxidative stress and selenium-enriched.The PDA and MEA media were used as basic media. The effect of oxidative stress induced respectively by CUSO4 and H2O2 on the sclerotial differentiation, colony morphology, sclerotial morphology and sclerotial biomass and in sclerotium of PT95 and Q1 strains were studied. Under the condition of oxidative stress induced by CuSO4 and H2O2, the time of exudates and sclerotium initiation, the time of the sclerotium maturation of the two strains was advanced 1-3 day compared with the control. And the time of sclerotium maturation of Q1 strain was delayed 1-3 days than that of PT95 strain. Meanwhile, under different oxidative stress conditions, the colonies of two strains consisted of sclerotium with greater diameter. The sclerotial biomass of PT95 and Q1 strains had a positive correlation with the oxidative stress. The stronger the oxidative stress was, the higher the sclerotial biomass. The results showed that under unfavorable conditions, PT95 and Q1 strains could differentiate forming more sclerotium.In PDA and MEA media as basic media, the influence of oxidative stress induced by CuSO4 and H2O2 on carotenoids content, ascorbic acid content, and antioxidative properties in sclerotium of PT95 and Q1 strains was studied. Under the lower oxidative stress conditions, the carotenoids content, ascorbic acid content and total phenolic content in sclerotium were increased, and DPPH radical scavenging ability, ferrous ion chelating ability and reducing power of ethanol extracts from sclerotium of two strains were also increased. The results indicated that under lower oxidative stress condition, PT95 and Q1 strains could produce non-enzymatic antioxidants to adapt the unfavorable environment. However, under higher oxidative stress conditions, they need to form more sclerotium to help them through the adverse environment for long periods survival.At the same time, in PDA and MEA media as basic media, the influence of sodium selenite (Na2Se03) and selenomethionine (SeMet) on the sclerotial differentiation, Se content and antioxidant properties in sclerotium of PT95 and Q1 strains were studied. When added Na2Se03 and SeMet into two media, it was found that PDA media was not conducive to the sclerotial differentiation of PT95 and Ql strains. On the contrary, with the increase of Na2Se03 and SeMet concentration in MEA media, the time of exudates initiation, time of sclerotial initiation and time of sclerotial maturation of both strains delayed. Compared with the control, the carotenoids content in sclerotium increased significantly, ascorbic acid content in sclerotium also increased, total phenolic content didn’t improve; reducing power of ethanol extracts from sclerotium of two strains were improved, the ferrous ion chelating ability and DPPH free radical scavenging activity didn’t improve. At the same time, accumulation of Se in sclerotium of PT95 and Ql strains was detected. On MEA media, the selenium content of PT95 strain’s sclerotium had a significant positive correlation with Na2Se03 and SeMet concentrations in media, the selenium content of Q1 strain’s sclerotium had a significant positive correlation with SeMet concentration, but had a weak positive correlation with Na2Se03 concentration. In order to improve the selenium content in sclerotium of PT95 and Q1 strains, the selenium-enriched media was optimized by orthogonal experiments. The optimum media was the following:SeMet of 15μg/mL, glucose of 13.33mg/mL, malt extract of 23.33mg/mL, peptone of 1 mg/mL, agar of 20 mg/mL.