| We selected four dark septate endophyte(Exophiala salmonis,Phialophora mustea, Paraphoma chrysanthemicola,Cladosporium cladosporioides) with high tolerance to lead as the object for study, which were isolated from the roots of Astragalus adsurgens of Qiandongshan Pb-Zn mine. we optimized the culture conditions of these fungi and investigated the biosynthesis of its melanin, and compared the adsorption capacity for lead of four dark septate endophytes, screening one strain with high adsorption capacity to further study its adsorption properties. The main results as follows:Under solid culture conditions, the optimum carbon source was glucose except for C. cladosporioides, which showed the highest growth on lactose; the optimum nitrogen source of P. chrysanthemicola was tryptone, while the optimum nitrogen sources of all others were sodium nitrate; the optimum combination of carbon-nitrogen source was glucose and peptone for both P. mustea and P. chrysanthemicola, but was glucose and sodium nitrate or urea, glucose and tryptone for E. salmonis and C. cladosporioides, respectively.Under submerged culture conditions, the optimum carbon source of E. salmonis was glucose, while the optimum carbon sources of all others were soluble starch; the optimum nitrogen source of E. salmonis, P. mustea, P. chrysanthemicola and C. cladosporioides was diammonium phosphate, ammonium oxalate, peptone, ammonium nitrate, respectively; the optimum combination of carbon-nitrogen source was soluble starch and ammonium nitrate for both C. cladosporioides and P. mustea, but was glucose and sodium nitrate, soluble starch and tryptone for E. salmonis and P. Chrysanthemicola, respectively.Under solid and submerged culture conditions, the optimum growth temperature for the four tested fungi was all 25 ℃, so they all belong to the moderate temperature fungi; the optimum p H values were 6.0 for both P. mustea and C. cladosporioides, but were 5.0 and 7.0 for E. salmonis and P. chrysanthemicola respectively. Under submerged culture conditions, for the tested fungi, the optimum agitation speed was 120 rpm except for P. mustea, which showed the highest growth at the 100 rpm.In Liquid culture condition, adding tricyclazole can make the color of the culture filtrate of E. salmonis and C. cladosporioides becoming reddish brown, but cann’t change the color of the culture filtrate of P. mustea and P. chrysanthemicola. Adding 2-Mercaptobenzimidazole cann’t make the color of the culture filtrate of four fungi having any change. The four fungi showed various tolerance to inhibitors used in test, the existence of inhibitors can hinder the growth of fungi. The melanin of E. salmonis and C. cladosporioides was synthesized via the DHN pathway, while the P. mustea and P. chrysanthemicola didn’t synthesize DHN or L-DOPA melanin.Comparing the lead adsorption capacity of four kinds of fungi, the results showed that the four tested fungi have significant effect on the adsorption of lead. The adsorption effect of lead is C. cladosporioides, P. chrysanthemicola, E. salmonis, P. mustea in turn. With the adsorption time for 60 min, the adsorption capacity and removal percentage of them for lead was 94.9% and 19.5 mg/g, 61.6% and 12.7 mg/g, 56.4% and 11.6 mg/g, 48.6% and 10.0 mg/g in the order.The adsorption capacity of inactive hyphae of C cladosporioides was highest in the four tested fungi. The Pb(II) biosorption on C. cladosporioides was signifficantly effected by p H, inital iron metal concertration, adsorption time, adsorbent dosage, temperature, agitation speed and pretreatment method of adsorbent. The maximum removal percentage was found to be 40.8 mg/g for Pb(II) at p H 5.0, inital iron metal concertration 150 mg/L, adsorbent dosage 3 g/L, temperature 25 ℃ and agitation speed 180 rpm with an equilibrium time of 120 min. The adsorption capacity of C. cladosporioides growing 10 d~13 d on MMN medium was better. The effect of different pretreatment methods on the adsorption capacity of inactive hyphae of C. cladosporioides was significantly. The adsorption capacity of C. cladosporioides growing 10 d~13 d on MMN medium was better. Suitable drying temperature and time was 80 ℃ and 12 h respectively. Commercial detergent and Na OH treatment can enhance the adsorption capacity by 36.3% and 26.3% respectively, and the former is better than the latte(p<0.05). The Pb(II) adsorption capacity and removal percentage of C. cladosporioides hyphae was reduced 2.94% and 2.91% respectively, because the melanin biosynthesis was inhibited by tricydazole. |
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