Phenol Removal Capacity of the Common Duckweed (Lemna minor L.) and Six Phenol-Resistant Bacterial Strains From Its Rhizosphere: In Vitro Evaluation at High Phenol Concentrations.

Olga Radulović,Slaviša Stanković,Vojin Tadić,Jelena Lozo,Marija Marković,Milana Trifunović-Momčilov,Branka Uzelac

doi:10.3390/plants9050599

Olga Radulović, Slaviša Stanković + Show 5 more

Open Access

https://doi.org/10.3390/plants9050599

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Abstract

The main topic of this study is the bioremediation potential of the common duckweed, Lemna minor L., and selected rhizospheric bacterial strains in removing phenol from aqueous environments at extremely high initial phenol concentrations. To that end, fluorescence microscopy, MIC tests, biofilm formation, the phenol removal test (4-AAP method), the Salkowski essay, and studies of multiplication rates of sterile and inoculated duckweed in MS medium with phenol (200, 500, 750, and 1000 mg L−1) were conducted. Out of seven bacterial strains, six were identified as epiphytes or endophytes that efficiently removed phenol. The phenol removal experiment showed that the bacteria/duckweed system was more efficient during the first 24 h compared to the sterile duckweed control group. At the end of this experiment, almost 90% of the initial phenol concentration was removed by both groups, respectively. The bacteria stimulated the duckweed multiplication even at a high bacterial population density (>105 CFU mL−1) over a prolonged period of time (14 days). All bacterial strains were sensitive to all the applied antibiotics and formed biofilms in vitro. The dual bacteria/duckweed system, especially the one containing strain 43-Hafnia paralvei C32-106/3, Accession No. MF526939, had a number of characteristics that are advantageous in bioremediation, such as high phenol removal efficiency, biofilm formation, safety (antibiotic sensitivity), and stimulation of duckweed multiplication.

Highlights

Phenol and its derivatives are used in all fields of industry
There was no statistical difference within the group grown in MS medium supplemented with phenol
Biofilm formation by bacteria grown in LB medium was greater when compared to bacteria grown in MS medium supplemented with phenol

Summary

Introduction

Phenol and its derivatives are used in all fields of industry. Excessive industrial growth, especially in developing countries, results in the constant influx of phenol into the environment worldwide [1]. Phenol is toxic even at very low concentrations (2 mg L−1 ) and is notoriously hard to eliminate by standard physical and chemical methods [2]. Bioremediation, i.e., the use of the natural ability of some organisms to detoxify their surroundings, is proposed as a welcome alternative, especially in cases when large areas are affected [1,2,3,4,5]. In addition to constant background leaks of phenol from hospitals, households, and factories, catastrophic leaks of >1 ton of phenol are relatively rare, but not uncommon in many countries worldwide.

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