Use of novel biological materials as adsorbents for removal of xenobiotics is gaining significance owing to their exceptional advantages. An extracellular polymeric substance (EPS) produced by Lysinibacillus sp. SS1 had rough porous surface as observed by SEM analysis. Adsorption ability of EPS was estimated against various textile dyes such as Malachite Green (MG), Methyl Orange, Congo Red and Coomassie Blue. About 82% of MG (100 mg/L) was adsorbed onto 2.5 mg EPS within 30 min. Effect of MG concentration, EPS weight, agitation speed and incubation time on adsorption, studied by one factor at a time approach, revealed that adsorption was influenced by all factors. Maximum adsorption of 99.01 ± 0.61% was achieved at 100 mg/L MG, 10 mg EPS, 120 RPM in 75 min with maximum adsorption capacity of 247.5 mg/g. Kinetics was affected by MG and EPS amounts, with shift from pseudo first to pseudo second order with increase in concentration. Adsorption of MG by EPS of Lysinibacillus sp. SS1 was identified as unilayer chemisorption as it followed Langmuir isotherm with maximum adsorption capacity ( Q m ) of 178.57 mg/g ( R 2 = 0.9889). This is the first report on potential of EPS produced by Lysinibacillus sp. SS1 as novel biodegradable adsorbent with high efficacy of MG removal from aqueous solutions.

The use of microbial extracellular polymeric substances (EPS) as bioflocculants opposed to synthetic and organic flocculants in the treatment of heavy metal polluted wastewater is currently gaining importance. The present study focuses on the characterization and application of EPS produced by Lysinibacillus sp. SS1 in heavy metal removal. Lysinibacillus sp. SS1 (10%v/v), isolated from used engine oil contaminated soil, produced EPS and circular white spongy masses on the utilization of 3% petroleum crude oil (PCO) in the Bushnell Haas medium in 10 d. Analysis of extracted EPS and masses revealed that it contained carbohydrates, lipids, and proteins in proportions of 1.3: 94.6: 3.6 and 2.3: 91.5: 6.2, respectively. Characterization by LCMS and FT-IR analysis confirmed that they were predominantly lipids with proteins and polysaccharide groups. Masses could remove 48% of lead and 40% of mercury from aqueous solutions by adsorption on their surface as confirmed by SEM-EDAX. Extracted EPS (100 mg/L) could remove 94.9% of lead from aqueous solution (150 mg/L) in 72 h by precipitation of lead as nanoparticles of sizes ranging from 30–40 nm. This study shows the potential of Lysinibacillus sp. SS1 and its EPS in response to PCO in heavy metal removal and recovery.

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