重金属胁迫对真菌生长及发酵液pH的影响

【背景】矿区废渣堆重金属污染严重,废渣堆分布着一些耐重金属的微生物。【目标】探究重金属胁迫对真菌生长及发酵液pH的影响。【方法】从金川矿区废渣堆采集土样,分离培养具有产酸能力的真菌,采用形态学与分子生物学技术鉴定这些菌株,并测定其产酸能力及其对Pb~(2+)、Cd~(2+)和Zn~(2+)的耐受性。【结果】形态学及18S rRNA基因序列分析获得黑曲霉ZJ-I (Aspergillus niger ZJ-I)和产黄青霉ZJ-V (Penicilium chrysogenum ZJ-V)两个产酸菌株。未加重金属培养时,与不接种真菌对照相比,上述2个菌株的发酵液pH分别下降0.58和0.69;添加重金属处理后,随着重金属浓度的增加,pH变化幅度变小,不同浓度Pb~(2+)使A.nigerZJ-I发酵液pH值分别下降0.53、0.39、0.34和0.39,使P. chrysogenum ZJ-V发酵液pH值分别下降0.21、0.23、0.14和0.09;不同浓度Cd~(2+)使A. niger ZJ-I发酵液pH值分别下降0.75、0.43、0.39和0.32,使P. chrysogenum ZJ-V发酵液pH值分别下降0.62、0.46、0.38和0.49;不同浓度Zn~(2+)可使A.nigerZJ-I发酵液pH分别下降0.87、0.61、0.57和0.43,使P. chrysogenum ZJ-V发酵液pH分别下降1.1、0.34、0.44和0.49;低浓度的Zn~(2+)对菌株A.niger ZJ-I和P. chrysogenum ZJ-V产酸都有促进作用,低浓度的Cd~(2+)对A. niger ZJ-I产酸有促进作用。当Cd~(2+)、Zn~(2+)与Pb~(2+)的浓度分别超过200、400、2 000 mg/L时,3种不同浓度的重金属对菌株A. niger ZJ-I的抑制率达到80%以上,抑制效果显著;当Cd~(2+)、Zn~(2+)与Pb~(2+)浓度分别超过200、1 000、2 000 mg/L时,3种不同浓度的重金属对菌株P.chrysogenumZJ-V抑制率达到80%以上,抑制效果显著。【结论】两株真菌均具有产酸能力和一定的重金属耐受性,菌株P. chrysogenum ZJ-V发酵液产酸性能与重金属耐受能力都要优于ZJ-I,菌株ZJ-V具备潜在的淋洗重金属污染土壤的能力。

Effect of heavy-metal stress on fungal growth and pH of fermentation broth

Background] Soil heavy metal pollution is serious in the slag heap of mining area. There are some microorganisms in the slag heap of mining area that are resistant to heavy metals. Objective] To investigate the effects of heavy metal stress on the growth of fungi and pH of fermentation broth. Methods] The acid-producing ability of two fungi (Aspergillus niger ZJ-I, Penicilium chrysogenum ZJ-V) isolated from the slag heap of mining area as materials and their tolerance to different heavy metal ions Pb2+, Cd2+ and Zn2+ were studied by using traditional microbial culture method. Results] The results showed that these two strains ZJ-I and ZJ-V were Aspergillus niger and Penicillium chrysogenum respectively by morphological and 18S rRNA gene sequence analysis. When the metal culture was not increased, the pH of the fermentation broth of the above two strains decreased by 0.58 and 0.69, respectively, compared with the control without inoculation of fungi and when the two strains were under heavy metal tolerance, the pH range decreased with the increase of heavy metal concentration, pH of the fermentation broth with different concentrations of Pb2+ decreased by 0.53, 0.39, 0.34 and 0.39 respectively, and by 0.21, 0.23, 0.14 and 0.09 respectively to P. chrysogenum ZJ-V. The pH of the fermentation broth with different concentrations of Cd2+ was decreased by 0.75, 0.43, 0.39 and 0.32 respectively on A. niger ZJ-I and 0.62, 0.46, 0.38 and 0.49 respectively on P. chrysogenum ZJ-V. The pH of the fermentation broth with different concentrations of Zn2+ decreased by 0.87, 0.61, 0.57 and 0.43 respectively, by 1.1, 0.34, 0.44 and 0.49 respectively to P. chrysogenum ZJ-V. The low concentration of Zn2+ promoted the acid production of A. niger ZJ-I and P. Chrysogenum ZJ-V, and the low concentration of Cd2+ promoted the acid production of A. niger ZJ-I. When the concentration of heavy metal ions Cd2+, Zn2+ and Pb2+ was more than 200, 400, 2 000 mg/L respectively, A. niger ZJ-I had significant inhibition rate reached 80%, when the concentration of heavy metal ions Cd2+, Zn2+ and Pb2+ was more than 200, 1 000, 2 000 mg/L respectively, P. chrysogenum ZJ-V had significant inhibition rate reached 80%, Conclusion] Both fungi have acid production ability and heavy metal tolerance, strain P. chrysogenum ZJ-V is superior to A. niger ZJ-I in acid production and heavy metal tolerance, so strain P. chrysogenum ZJ-V can be used as the dominant strain for bioremediation of heavy metal contaminated soil.