Decolorization of Textile Dye by HalophilicExiguobacteriumsp.VK1: Biomass and Exopolysaccharide (EPS) Enhancement for Bioremediation of Malachite Green

Exopolysaccharide production by salt-tolerant bacteria: Recent advances, current challenges, and future prospects

Natural biopolymers derived from exopolysaccharides (EPSs) are considered eco-friendly and sustainable alternatives to available traditional synthetic counterparts. Salt-tolerant bacteria inhabiting harsh ecological niches have evolved a number of unique adaptation strategies allowing them to maintain cellular integrity and assuring their long-term survival; among these, producing EPSs can be adopted as an effective strategy to thrive under high-salt conditions. A great diversity of EPSs from salt-tolerant bacteria have attracted widespread attention recently. Because of factors such as their unique structural, physicochemical, and functional characteristics, EPSs are commercially valuable for the global market and their application potential in various sectors is promising. However, large-scale production and industrial development of these biopolymers are hindered by their low yields and high costs. Consequently, the research progress and future prospects of salt-tolerant bacterial EPSs must be systematically reviewed to further promote their application and commercialization. In this review, the structure and properties of EPSs produced by a variety of salt-tolerant bacterial strains isolated from different sources are summarized. Further, feasible strategies for solving production bottlenecks are discussed, which provides a scientific basis and direct reference for more scientific and rational EPS development.

Use of activated Chromolaena odorata biomass for the removal of crystal violet from aqueous solution: kinetic, equilibrium, and thermodynamic study

In the present study, biomass from the Chromolaena odorata plant's stem was activated using sulfuric acid to adsorb crystal violet (CV) dye. The adsorption operation of CV dye was studied considering the effect of variables like pH, initial dye concentration, time, adsorbent dosage, and temperature. The pseudo-second-order equation best fitted the kinetic study. The thermodynamic parameters such as activation energy (9.56 kJ/mol), change in Gibbs energy (81.43 to 96.7 kJ/mol), enthalpy change (6.89 kJ/mol), and entropy change (-254.4 J/mol K) were calculated. Response surface methodology estimated that at pH (4.902), adsorbent dosage (8.33 g/L), dye concentration (82.30 ppm), and temperature (300.13 K) dye removal of 97.53% is possible. FTIR, SEM, XRD, BJH, and BET confirmed adsorption operation. The adsorbent can be reused for 3 cycles effectively. Langmuir isotherm which best fitted the adsorption operation was used for designing a theoretical single-stage batch adsorber for large-scale operation.

Exopolysaccharides from marine microbes with prowess for environment cleanup

A variety of both small and large biologically intriguing compounds can be found abundantly in the marine environment. Researchers are particularly interested in marine bacteria because they can produce classes of bioactive secondary metabolites that are structurally diverse. The main secondary metabolites produced by marine bacteria are regarded as steroids, alkaloids, peptides, terpenoids, biopolymers, and polyketides. The global urbanization leads to the increased use of organic pollutants that are both persistent and toxic for humans, other life forms and tend to biomagnified in environment. The issue can be addressed, by using marine microbial biopolymers with ability for increased bioremediation. Amongst biopolymers, the exopolysaccharides (EPS) are the most prominent under adverse environmental stress conditions. The present review emphasizes the use of EPS as a bio-flocculent for wastewater treatment, as an adsorbent for the removal of textile dye and heavy metals from industrial effluents. The biofilm-forming ability of EPS helps with soil reclamation and reduces soil erosion. EPS are an obvious choice being environmentally friendly and cost-effective in processes for developing sustainable technology. However, a better understanding of EPS biosynthetic pathways and further developing novel sustainable technologies is desirable and certainly will pave the way for efficient usage of EPS for environment cleanup.

Adsorption of Malachite Green by extracellular polymeric substance of Lysinibacillus sp. SS1: kinetics and isotherms

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.