Response surface algorithm for improved biotransformation of 1,4-dioxane using Staphylococcus capitis strain AG.

The present investigation reports the biotransformation of an endrocrine disrupting agent; 1,4-dioxane through bacterial metabolism. Initially, potential bacterial isolates capable of surviving with minimum 1,4-dioxane were screened from industrial wastewater. Thereafter, screening was done to isolate a bacteria which can biotransform higher concentration (1000 mg/L) of 1,4-dioxane. Morphological and biochemical features were examined prior establishing their phylogenetic relationships and the bacterium was identified as Staphylococcus capitis strain AG. Biotransformation experiments were tailored using response surface tool and predictions were made to elucidate the opimal conditions. Critical factors influencing bio-transformation efficiency such as tetrahydrofuran, availability of 1,4-dioxane and inoculum size were varied at three different levels as per the central composite design for ameliorating 1,4-dioxane removal. Functional attenuation of 1,4-dioxane by S. capitis strain AG were understood using spectroscopic techniques were significant changes in the peak positions and chemical shifts were visualized. Mass spectral profile revealed that 1.5 (% v/v) S. capitis strain AG could completely (∼99%) remove 1000 mg/L 1,4-dioxane, when incubated with 2 µg/L tetrahydrofuran for 96 h. The toxicity of 1,4-dioxane and biotransformed products by S. capitis strain AG were tested on Artemia salina. The results of toxicity tests revealed that the metabolic products were less toxic as they exerted minimal mortality rate after 48 h exposure. Thus, this research would be the first to report the response prediction and precise tailoring of 1,4-dioxane biotransformation using S. captis strain AG.

Chemo-metrically formulated consortium with selectively screened bacterial strains for ameliorated biotransformation and detoxification of 1,4-dioxane.

The biotransformation of 1,4-dioxane, a endrocrine disrupting chemical was achieved using different bacterial strains and their consortia. Three different bacterial isolates were screened on their ability to grow with 50 mg/L 1,4-dioxane in the basal mineral medium. Then the isolates were tested for its efficiency to biotransform 1000 mg/L 1,4-dioxane at varying period of time; 24-120 h. The isolates were distinguished by their morphological features and 16 S rRNA gene sequencing was done to evaluate the phylogenetic relationships. The isolates were identified as Bacillus marisflavi strain MGA, Aeromonas hydrophila strain AG and Shewanella putrefaciens strain AG. The degree of biotransformation was escalated by constructing a bacterial consortium using statistical tool; response-mixture matrix under the design of experiments. The fully grown bacterial strains were used as ingredients in different proportions to formulate the consortium. The biotransformation was analyzed for functional attenuation using spectroscopic techniques and reduction in 1,4-dioxane level was confirmed using mass spectrometry. The precise quantification of biotransformation using mass spectral profile revealed that the consortium removed 31%, 61% and 85% of 1000 mg/L 1,4-dioxane within 96, 120 and 144 h respectively. The activities of inducible laccase were elucidated during biotransformation of 1,4-dioxane. Bio-toxicity of treated and untreated 1,4-dioxane on brine shrimp; Artemia salina showed that the biotransformed products were less toxic. Therefore, this report would be first of its kind to report the biotransformation and detoxification of 1,4-dioxane by a statistically designed bacterial consortium.

Kinetic modelling of high turbid water flocculation using native and surface functionalized coagulants prepared from shed-leaves of Avicennia marina plants.

Coagulation performance of shed-leaves of Avicennia marina plants collected from Alang coastline, Gujarat (India) was scrutinized for the treatment of mud and starch water suspensions. For which, native, hydrochloric acid, sodium hydroxide and sodium chloride treated A. marina shed-leaves were processed with minimum environmental impact. Experiments were accomplished for the concentration of water suspensions (10-50 g/L) at the range of pH 7.0-8.0. The performances of these coagulants were assessed in terms of reduction in turbidity, pH, alkalinity, hardness, electrical conductivity and solids from water suspensions. The removal of bulk impurities was noted due to the floc formation of coagulant through hydrolysing salts, thus, resulted in the highest settlement at pH 7.82, 7.90 for mud and starch water, accordingly. Native and functionalized A. marina coagulants (AMCs) were characterized and interpreted using scanning electron microscopy, elemental analyses, energy dispersive and Fourier transform infrared spectroscopy. HCl treated AMC was relatively effective with good coagulation performance (96.76%), when compared with native and other treated AMCs. The turbidity removal by all AMCs obeyed with World Health Organization (WHO) acceptable limit of finished water, where HCl treated AMC clarified 15.15 and 16.36 NTU of mud and starch water suspensions to produce a clear water of 0.92 and 1.61 NTU, respectively. The proficiency of prepared AMCs were compared with other natural coagulants and surface functionalized (HCl > NaOH > NaCl) AMCs prepared in this study exerted better performance than the native AMC. The critical coagulation rate from the second-order kinetics were evaluated and the results were highly satisfying. Other physico-chemical parameters of water suspensions were evident for the adequate removal of impurities by non-toxic plant-based coagulants.