黑曲霉RAF106菌丝球形成的影响因素及对结晶紫的吸附作用

The pellet-formation factors of Aspergillus niger RAF106 and its application in the biosorption of crystal violet

摘要:

[背景] 黑曲霉（Aspergillus niger）作为一种代表性丝状真菌已被广泛用于酶制剂、有机酸、抗生素等高价值代谢产物的工业生产、食品发酵、环境治理等行业，其代谢能力、发酵性能等与菌体形态密切相关。然而，黑曲霉对染料、重金属等的吸附能力与菌体形态的关系鲜有报道。[目的] 探究黑曲霉菌丝球形成的影响因素及其对结晶紫的吸附作用。[方法] 以从普洱茶分离的黑曲霉RAF106为研究对象，实时监测马铃薯葡萄糖培养液中黑曲霉菌丝球的形成过程；探究培养液的初始pH （4.0-10.0）、培养温度（25-45 ℃）、孢子接种量（5×10⁴-5×10⁶个/mL）、摇床转速（140-220 r/min）、碳源（葡萄糖、蔗糖、果糖、乳糖、醋酸钠）和氮源（硝酸钠、胰蛋白胨、酵母提取粉、氯化铵）对菌丝球形成的影响；以结晶紫为对象，研究不同菌体形态及菌丝球大小对黑曲霉吸附废水染料能力的影响。[结果] 在黑曲霉RAF106中，孢子聚集、菌丝聚集均可形成菌丝球；菌丝球的大小与培养液初始pH、孢子接种量成反比，与摇床转速无关；当温度低于35 ℃时，菌丝球大小与温度成正比，温度高于35 ℃时菌丝球大小与温度成反比，45 ℃时菌丝球无法形成；对碳源和氮源而言，葡萄糖更利于菌丝球的形成，而氮源的添加不利于菌丝球的形成。菌丝球生物量与所测定的初始pH、摇床转速及温度无关，与接种量成正比，而且受不同碳氮源的影响；菌丝球直径越小，对结晶紫吸附能力越强，而相较于菌丝球，分散菌丝更有利于吸附结晶紫。[结论] 黑曲霉RAF106菌丝球的大小受初始pH、温度和孢子接种量的调控，但不受摇床转速影响，而菌体形态与其对结晶紫的吸附能力密切相关。研究结果为优化黑曲霉菌体形态控制体系及废水处理体系提供了依据。

Abstract:

[Background] Aspergillus niger, a typical filamentous fungus, can produce valuable metabolites, such as enzymes, organic acids, antibiotics, and is widely used in food fermentation, environment protection and so on. Its physiological characters including fungal metabolism and productivity are closely associated with fungal morphologies. However, the relationship between fungal morphologies and the biosorption of dyes and heavy metals is little known. [Objective] To study the pellet-formation factors of A. niger RAF106 and its application in the biosorption of crystal violet. [Methods] The dynamic processes of pellet formation, the effects of the initial pH, temperature, spore inoculum level, agitation frequency, and different carbon and nitrogen sources on pellet formation, and the effects of different morphologies on the biosorption of crystal violet were investigated in tea-derived A. niger RAF106 when incubated in the medium of potato dextrose broth (PDB). [Results] Both conidia and hypha can aggregate and then form pellets in A. niger RAF106. The diameters of pellets were inversely proportional to the initial pH values ranging from 4.0 to 10.0 and spore inoculum levels ranging from 5×10⁴ to 5×10⁶ but had nothing to do with agitation frequency. Moreover, the diameters increased with the increase of culture temperature ranging from 25℃ to 35℃ but decreased with the increase of culture temperature ranging from 35℃ to 40℃, and pellets can not be formed at 45℃. Additionally, the diameters of pellets in the group of glucose are the biggest among the tested groups treated with different carbon sources, but the addition of exogenous nitrogen sources inhibited the diameters. In addition, the fungal biomass was not affected by tested initial pH, temperature, and agitation frequency but positively correlated with spore inoculum levels, and affected by different carbon and nitrogen sources. Furthermore, more crystal violet can be absorbed by smaller pellets than that in bigger pellets, and hypha was the most effective one. [Conclusion] The diameters of pellets are affected by temperature, initial pH, inoculum levels as well as carbon and nitrogen source but not shaker speed. The adsorption of crystal violet depends on fungal morphologies in A. niger RAF106. These results will be helpful to control the fungal morphologies and optimize the wastewater treatment system associated with A. niger.