纳米氧化锌对白地霉生长和胞外降解酶活性的影响

Effects of Nano-sized Zinc Oxide on the Growth and Extracellular Degrading Enzyme Activity of Geotrichum candidum

关键词:  纳米氧化锌  白地霉  生物量  胞外降解酶  生态毒性

Key words:  nano-sized zinc oxide  fungi  biomass  enzyme activity  eco-toxicity

摘要:

随着纳米科技的兴起，纳米材料在医学、传感器和精细化工等多个领域发挥着重要作用，但由此产生的纳米材料废弃物可通过人类活动、大气沉降、地表及地下径流等途径进入淡水环境中，对水环境健康构成了潜在的威胁。为探究纳米氧化锌对真菌生长和代谢功能的生态毒性，本研究评估了不同浓度（0.1，0.5，1，5，10和20 mg/L）纳米氧化锌对白地霉（Geotrichum candidum）培养环境pH、生长特征（菌丝鲜重和干重）以及胞外降解酶（酸性磷酸酶、亮氨酸氨基肽酶、纤维二糖水解酶和过氧化物酶）活性的影响。结果表明，纳米氧化锌暴露对真菌培养环境的pH条件没有显著影响。在急性暴露下，1 mg/L纳米氧化锌处理能使真菌鲜重和干重显著降低，而20 mg/L浓度时则相反。此外，低浓度（0.1 mg/L）纳米氧化锌可促进4种胞外降解酶活性，高浓度（5-20 mg/L）时则出现抑制作用，但这种抑制作用在慢性暴露下会减弱甚至转变为促进作用。综上所述，随着暴露时间的推移，白地霉对高浓度纳米氧化锌产生一定的耐受性。未来应进一步探究白地霉作为功能菌种修复纳米材料污染的淡水生态系统的潜力。

Abstract:

Nano-materials play an important role in many fields such as medicine, sensors and the fine chemical industry with the rise of nanotechnology. However, a large amount of nano-material waste can enter into the freshwater environment through human activities, atmospheric deposition as well as surface and underground runoff, which poses a potential threat to the health of aquatic environments. To explore the eco-toxicity of nano-sized zinc oxide on fungal growth and metabolic function, this study evaluated the effects of nanosized zinc oxide at different concentrations (0.1, 0.5, 5, 10, and 20 mg/L) on culture environment pH, growth characteristics (fresh and dry weights of mycelia), and extracellular enzymes (acid phosphatase, leucine aminopeptidase, cellobiohydrolase, and peroxidase) of Geotrichum candidum. The results showed that exposure of nano-sized zinc oxide had no significant effect on pH conditions of fungal culture environment.Under acute exposure, the fresh and dry weights of fungi were significantly decreased by 1 mg/L nano-sized zinc oxide, while were significantly increased by 20 mg/L nano-sized zinc oxide. Besides, nano-sized zinc oxide at low concentrations (0.1 mg/L) significantly promoted the activities of four extracellular degrading enzymes. Nano-sized zinc oxide at higher concentrations (5-20 mg/L) showed inhibitory effects on the activities of four extracellular degrading enzymes under acute exposure, while the inhibitory effects were weakened or even turned into promoting effects under chronic exposure. In summary, as the exposure time went on, Geotrichum candidum had certain tolerance to high-concentration nanosized zinc oxide. In the future, the potential of Geotrichum candidum as a functional strain to repair freshwater ecosystems contaminated by nano-materials should be further explored.