Production of di-rhamnolipid with simultaneous distillery wastewater degradation and detoxification by newly isolated Pseudomonas aeruginosa SRRBL1

Distillery industries generate around 12–15 L aqueous waste per liter of alcohol production. Characteristics of distillery wastewater (DWW) dark brown color containing organic and inorganic pollutants with heavy metals (HMs) cause pernicious effects on the terrestrial and aquatic ecosystems. Unknowingly untreated DWW irrigation adversely affects the productivity of the crops due to the unavailability of minerals, reduction in seed germination and seedling growth. So, this study screened potential isolates that have plant growth promotion (PGP) and biosurfactant (BS) production properties. 5% inoculum of Pseudomonas aeruginosa SRRBL1 produced 2.9 g/L BS from minimal salt media (MSM) amended with 20% (v/v) DWW at 37 °C and 120 revolutions per minute (rpm) after 72 h incubation. Thin-layer chromatography (TLC), Fourier transform-infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹H NMR) and liquid chromatography-mass spectrometry (LC-MS) analysis indicated that extracted BS was di-rhamnolipid in nature. Simultaneously SRRBL1 reduced color, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), heavy metals (HMs) such as iron (Fe), zinc (Zn), nickel (Ni), lead (Pb), cadmium (Cd) and chromium (Cr) were 61.76%, 53.53%, 61.32%, 56.61% 74.44%, 70.76%, 51.56%, 73.06% 58.96% and 27.49%, respectively from DWW. In addition, FT-IR and gas chromatography-mass spectrometry (GC-MS) identify functional groups and metabolites found in DWW. Major identified metabolites listed as endocrine disruptive chemicals (EDCs) such as octadecane; heneicosane; 1,2-Benzenedicarboxylic acid, butyl 8-methylnonyl ester; oxirane, tetradecyl-; 1,4-Dioxane-2,5-diol, 2TBDMS derivative; n-tetracosanol-1 octadecanoic acid and hexadecanoic acid in untreated DWW were diminished and some new metabolites produced after bacterial treatment. Furthermore, phytotoxicity assay on Triticum aestivum confirmed that treated wastewater enhanced seed germination up to 73%. Hence it indicated that SRRBL1 can be applied for di-rhamnolipid production from DWW with simultaneous pollutants reduction.