Degradation of SDS by psychrotolerant Staphylococcus saprophyticus and Bacillus pumilus isolated from Southern Ocean water samples

Abstract

Bioremediation of surfactants in water bodies holds significant ecological importance as they are contaminants of emerging concern posing substantial threats to the aquatic environment. Microbes exhibiting special ability in terms of bioremediation of contaminants have always been reported to thrive in extraordinary environmental conditions that can be extreme in terms of temperature, lack of nutrients, and salinity. Therefore, in the present investigation, a total of 46 bacterial isolates were isolated from the Indian sector of the Southern Ocean and screened for degradation of sodium dodecyl sulphate (SDS). Further, two Gram-positive psychrotolerant bacterial strains, ASOI-01 and ASOI-02 were identified with significant SDS degradation potential. These isolates were further studied for growth optimization under different environmental conditions. The strains were characterized as Staphylococcus saprophyticus and Bacillus pumilus based on morphological, biochemical, and molecular (16S RNA gene) characteristics. The study reports 88.9% and 93.4% degradation of SDS at a concentration of 100 mgL^-1, at 20 °C, and pH 7 by S. saprophyticus ASOI-01 and B. pumilus ASOI-02, respectively. The experiments were also conducted in wastewater samples where a slight reduction in degradation efficiency was observed with strains ASOI-01 and ASOI-02 exhibiting 76.83 and 64.93% degradation of SDS respectively. This study infers that these bacteria can be used for the bioremediation of anionic surfactants from water bodies and establishes the potential of extremophilic microbes for the utilization of sustainable wastewater management.

Keywords: 16S rRNA; Bioremediation; Emerging pollutants; Extremophiles; Growth optimization; SDS.

Fig. 1

a Set of instruments performing CTD operations for collection of water samples from different depths, b Cruise track for the expedition to the Southern Ocean, and c Stations for collection of water samples in the Indian Sector of Southern Ocean

Fig. 2

A Optimization of growth of ASOI-01 with changing parameters, viz., concentration, temperature, and pH. The strain ASOI-01showed the maximum growth at 100 mgL⁻¹ substrate concentration, 20 °C temperature and 7 pH. B Surface plot of growth of ASOI-01 at (a) 5 pH, (b) 7 pH, (c) 8 pH with respect to SDS concentrations and temperatures at 4, 20, and 37 °C respectively

Fig. 3

A Optimization of growth of ASOI-02 with changing parameters, viz., concentration, temperature, and pH. The strain ASOI-02 showed the maximum growth at 200 mgL⁻¹ substrate concentration, 20 °C temperature and 7 pH. B Surface plot of growth of ASOI-02 at (a) 5 pH, (b) 7pH, (c) 8 pH with respect to SDS concentrations and temperatures at 4, 20, and 37 °C, respectively

Fig. 4

Graphical representation of degradation of SDS using ASOI-01 and ASOI-02 with respect to time. A maximum degradation of 88.87 and 93.41% was achieved with ASOI-01 and ASOI-02 respectively

Fig. 5

Graphical representation of validation of biodegradation experiment conducted in wastewater sample, showing degradation of SDS by strains ASOI-01 and ASOI-02 with respect to time

Fig. 6

Phylogenetic tree of the nearest neighbours of ASOI-01

Fig. 7

Phylogenetic tree of the nearest neighbours of ASOI-02