一株富硒菌的鉴定及富硒条件优化

Identification of selenium-enriched strain of bacteria and the optimization of conditions for selenium enrichment

微生物在硒的生物和环境循环中扮演着重要角色,许多微生物能将Se(IV)和Se(VI)还原为低毒的Se(0)并形成纳米硒微粒,这些生物源的纳米硒微粒在环境修复、生物传感器和医学等领域有着广泛的应用前景。研究天然富硒菌的富硒条件对于富硒微生物的应用具有重要意义。本研究利用16S r DNA测序、生理和形态特征对实验室保存的富硒菌WNJ40进行菌种鉴定,并通过扫描电镜(SEM)观察亚硒酸钠对菌株的影响,同时在单因素实验的基础上,应用响应面法对富硒菌株的富硒条件进行方法设计、优化并验证富硒方案。结果表明:富硒菌株WNJ40经鉴定为变形菌门γ-变形菌纲肠杆菌目肠杆菌科的Serratia marcescens。SEM分析表明,菌株WNJ40在含亚硒酸钠的培养基中生长能产出直径在100~800 nm的球形微粒聚集体。响应面法优化后的最佳富硒发酵条件为:接种量8%,转速120 r·min^(-1),培养时间为58 h,在此优化条件下,菌株富硒量为248.70 mg·L^(-1),较优化前提高了22.74%,为菌株的应用提供了理论和实践基础。

Microorganisms play a key role in selenium cycling.Many microorganisms could reduce Se(IV)and Se(VI)to less toxic Se(0)with the formation of Se nanoparticles(SeNPs),which are eventually exploitable in the fields of environmental remediation,biosensors,and medicine.It is of great significance to optimize the conditions of selenium enrichment for the application of selenium-enriched microorganisms.In this study,the strain WNJ40 isolated from Se-laden soil was identified by sequence analysis of 16 S r DNA technique,physiological and morphological characteristics.The effect of sodium selenite on the strain was observed by scan electron microscopy(SEM).Based on single-factor experiments,the response surface methodology was performed to design,optimize,and verify the selenium enrichment condition of strain WNJ40.The results showed that:(1)The strain WNJ40 was identified as Serratia marcescens.(2)Results of SEM analysis showed that spherical aggregations with diameters of 100-800 nm were produced when strain WNJ40 grew in the medium containing sodium selenite.(3)The optimal fermentation conditions were determined as:8%of inoculation,120 r·min^(-1) of rotation speed,and 58 h of fermentation time.Under the optimization conditions,selenium enrichment by the strain was248.70 mg·L^(-1),which was 22.74%higher than that before the optimization.Our results provide a theoretical and practical basis for the application of the strain.