Guangxi Zhiwu (Jul 2023)
Isolation and characterization of autotoxic saponins-degrading bacterial strains from Panax notoginseng
Abstract
Panax notoginseng is a valuable Chinese herb in China, and the root should be harvested between three and seven years after planting it. However, the growth of P. notoginseng is frequently hindered due to replanting failure. There have been numerous studies proving that the accumulation of allelochemicals in the soil is considered to be one of the reasons for the replanting failure of P. notoginseng. Biodegradation of allelochemical in soil has been shown to be an effective measure to alleviate continuous cropping obstacles, so screening allelochemical-degrading bacteria could provide biological resources for soil remediation. Based on this, this study adopted a research strategy of enrichment and domestication to isolate and screen saponin-degrading bacteria from the rhizosphere soil of P. notoginseng, which had been grown continuously for three years and more. Also, the highly active strains were identified by 16S rRNA gene analysis. In addition, the effect of highly active strain SC3 on degrading allelochemicals under different conditions was studied by HPLC. The results were as follows: (1) Eight strains of potentially degrading bacteria were successfully isolated from the rhizosphere soil of P. notoginseng. The results of the initial screening evaluation showed that strain SC3 had the best biodegradation effect on total saponins with 87.42% degradation rate. (2) Strain SC3 was identified as Stenotrophomonas sp. based on 16S rRNA gene analysis coupled with physiological and biochemical analyses. (3) The biodegradation of ginsenoside Rb1 by strain SC3 was stronger than its biodegradation of ginsenoside Rg1 under the same culture conditions. (4) The degradation of ginsenoside Rb1 by SC3 strain under liquid culture conditions was significantly affected by different factors, such as substrate concentration, inoculum amount and culture temperature. All the results indicate that the enrichment and domestication strategy can effectively screen allelochemical-degrading bacteria, and a possible application of strain SC3 in the bioremediation of saponin contamination in agricultural environments. The results provide biological resources for replanting soil remediation and theoretical basis for further study of saponin degradation mechanism.
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