Studies On Optimization Of Culture Conditions And Properties Of The Yellow Pigment From A Strain Of Septafusidium Bifusisporum

A series studies on the yellow pigment from mycelia of Septafusidium bifusisporum were carried out. The studies included isolation and identification of pigment; CHO cytotoxicity assay for primary estimation of the pigment toxicity; culture conditions optimization with high yield fungal strain; extraction conditions optimization for further exploitation, and additionally, the pigment properties was also studied.HPLC-MS analysis showed that the pigment was a mixture. High resolution MS analysis revealed that the molecular formula of the main pigment component was C26H32O9. The pure compound has ultra-violet absorbance at 227nm and 411nm. Data base searching results showed that there was no matched compound in the natural products dictionary Chapman&Hall. Therefore, it was possibly a new compound.CHO-cytotoxicity-assay showed that the pigment extracted from mycelia of RCEF3669 had non toxicity. This means that the natural pigment is a safe pigment with good value of development.Based on the experiments for fermentation conditions of the pigment, the optimal composition of medium was optimized as: dextrose20g/L, glycerin 20 g/L, corn flour 30 g/L, soybean flour 20g/L, NH₄NO₃ 2g/L, MgSO₄·7H₂O 1.0g/L, KH₂PO₄ 3.0g/L, VB 0.4g/L, CaCl₂ 0.5g/L. The optimal culture condition was optimized as follows: seed age was 3d; inocula amount was 7.5%; culture temperature was 25℃, and culture duration was 10d。Extraction tests showed that the optimal method of soaking was as follows: the optimal solvent was methanol; the optimal temperature was 45℃; the extraction time was 120min; the material/liquid was 1:20, and the extracting grade was 2. By comparing the effect of ultrasonic and normal solvent extractions, it was found that ultrasonic assistant extraction had a better effect than normal solvent extraction. The optimal extraction conditions were as follows: the ultrasonic power was 80 w; the treat time was 40 min, and the extraction temperature was 40℃.Studies on properties of the pigment revealed that the pigment has a maximal absorption at 411 nm which was the same as the main components of the pigment. The pigment could be dissolved in methanol, acetonitrile, N-butanol and dimethylsulfoxide. It was relatively stable in darkness and under sunlight, but the UV-ray irradiation had a significant negative effect on its stability. The pigment was stable to heat and could endure certain high temperature(≤75℃). It was relatively stable to sodium hyposulfite, VC, sodium benzoate and sugar. Citric acid could enhance the color of the pigment, but hydrogen peroxide could reduce stability of the pigment significantly. As the treat time duration of H2O2 the pigment remanet ratio was reduced significantly. Stability tests on metal elements revealed that most metal ions had not significant bad effect on stability of the pigment, except that iron ion could reduce some absorbency of the pigment.