樊庆生红球菌菌剂制备优化及其重金属修复促进效果研究

Rhodococcus qingshengi inoculant preparation and its role in promoting efficient heavy metal phytoremediation

目前,土壤重金属污染形势严峻,而微生物辅助植物修复的措施以其绿色友好的特性备受关注,其中,研发高效的微生物菌剂对提高修复效率至关重要.针对一种能代谢植物激素脱落酸(ABA)的微生物-樊庆生红球菌(Rhodococcus qingshengii)进行菌剂制备研究,并验证其对超积累植物东南景天提取重金属镉(Cd)、铜(Cu)、镍(Ni)和锌(Zn)能力的强化效果.结果表明,该菌种制备优化条件为:80%麦麸∶15%锯末∶5%活性炭;料水比1∶2、pH=9;接菌量40%;培养温度30℃、培养时间3 d、烘干温度40℃.优化后,固体菌剂有效活菌数可达2×10^(12) CFU·g^(-1),与土壤混合后其有效活菌数峰值达1×10^(11) CFU·g^(-1),是接种相同活菌数液体菌剂的4倍,30 d保有的有效活菌数是液体菌剂的23倍.与未配施的空白相比,该菌剂配施于不同重金属污染土壤中,可使东南景天的Cd含量提高110%~260%,Ni和Zn含量分别提高约100%和90%;生物富集因子(BCF)则提高50%~500%,转运系数(TF)提高80%~250%.与配施菌液相比,固体菌剂的效果也更优,可使植物积累重金属能力提高15%~250%.结果证实,樊庆生红球菌固体菌剂的优化可大幅强化植物修复重金属污染土壤的效果,通过ABA代谢菌协同超积累植物修复重金属污染土壤,有望成为今后提升植物修复效率的新方法.

Soil heavy metal contamination is a serious global problem.Plant-microbe-assisted bioremediation is receiving increasing scientific attention due to its green and eco-friendly characteristics.Developing efficient bacterial agents to improve phytoremediation efficiency is crucial.In this study,we optimized the preparation of Rhodococcus qingshengi solid inoculants to metabolize the phytohormone abscisic acid(ABA)of plants,investigating its potential for improving heavy metal phytoremediation efficiency of cadmium(Cd),copper(Cu),nickel(Ni),and zinc(Zn).The results showed that the optimum preparation conditions were as follows:80%wheat bran,15%sawdust,and 5%activated carbon;1∶2 water to raw material ratio;pH=9;40%inoculum;30℃incubation temperature;a 3-day incubation period;and 40℃oven drying temperature.After optimization,the number of live bacteria reached 2×10^(12) CFU·g^(-1) in microbial inoculants.When microbial inoculants were mixed with soils,the peak number of live bacteria reached≤1×10^(11) CFU·g^(-1),whichwas four times than that in liquid inoculants that had the same number of viable bacteria.Moreover,the number of live bacteria after 30 days was 23 times than that in liquid inoculants.Compared to the non-inoculated control,the Cd contents of Sedum alfredii Hance grown in different contaminated soils increased by 110%~260%with inoculants,while the Ni and Zn contents increased by 100%and 90%,respectively.The biological enrichment factor and transfer factor of Sedum alfredii Hance increased by 50%~500%and 80%~250%,respectively,after being supplied with microbial inoculants.Compared with liquid inoculants,microbial inoculants were more efficient at increasing heavy metal accumulation in plants by 15%~250%.These results indicated that Rhodococcus qingshengi inoculants could enhance the phytoremediation efficiency of heavy metal contaminated soils.Therefore,this study has demonstrated a new strategy to improve phytoremediation using microbials that can metabolize ABA.