Bioremediation of petroleum wastewater by hyper-phenol tolerant Bacillus cereus: Preliminary studies with laboratory-scale batch process.

Petroleum wastewater samples from oil refinery and oil exploration site were treated by hyper phenol-tolerant Bacillus cereus (AKG1 and AKG2) in laboratory-scale batch process to assess their bioremediation efficacy. Quality of the treated wastewater samples were analyzed in terms of removal of chemical oxygen demand (COD), total organic carbon (TOC) and ammonium nitrogen content, and improvement of biological oxygen demand (BOD). Adaptation of these bacteria to the toxic environment through structural changes in their cell membranes was also highlighted. Among different combinations, the co-culture of AKG1 and AKG2 showed the best performance in degrading the wastewater samples.

Biodegradation of real petroleum wastewater by immobilized hyper phenol-tolerant strains of Bacillus cereus in a fluidized bed bioreactor.

Microbial bioremediation of petroleum wastewater by phenol-degrading-bacteria holds promise in circumventing the issue of petroleum-spill related pollution. Herein, biodegradation of petroleum wastewater samples collected from oil refinery site was carried out in a fluidized bed bioreactor by Ca-alginate immobilized biomass of phenol-degrading strains of Bacillus cereus (AKG1 MTCC9817 and AKG2 MTCC9818). Degradation performance of the system was evaluated by measuring the changes in chemical oxygen demand (COD) and level of phenolic compounds in the wastewater samples during the microbial treatment. The microbial treatment reduced initial COD level and concentration of phenolic compounds by 95 % or more, demonstrating the excellent efficacy of immobilized AKG1 and AKG2 strains in treating petroleum wastewater in continuous mode of operation. The present study demonstrates the potential of immobilized AKG1 and AKG2 in treating petroleum wastewater in fluidized bed bioreactors.

CO2 biofixation and carbonic anhydrase activity in Scenedesmus obliquus SA1 cultivated in large scale open system.

The present study deals with the large scale open system cultivation of the novel microalga: Scenedesmus obliquus SA1 (KC733762) previously isolated in our laboratory. SA1 strain was cultivated in open system at varying CO2 levels ranging from 0.03% to 35% (v/v) and subsequently the carbonic anhydrase activity (CA) and the biochemical properties were monitored. Maximum biomass concentration (1.39 ± 0.023 g L(-1)), CO2 fixation rate (97.65 ± 1.03 mg L(-1)d(-1)) and total CA activity (166.86 ± 3.30 E.U./mg chla) were obtained at 35% CO2. CA inhibitors: acetazolamide and ethoxyzolamide inhibited the external and internal enzyme activity in SA1. High CO2 levels were favorable for the accumulation of lipids and chlorophyll. The present results suggested that SA1 possessed high CO2 tolerance and high carbohydrate, lipid and chlorophyll content when cultivated in open system thus being suitable for CO2 mitigation in outdoor ponds and subsequent generation of value added products.

Enhanced CO2 sequestration by a novel microalga: Scenedesmus obliquus SA1 isolated from bio-diversity hotspot region of Assam, India.

The present study aimed to isolate a high CO2 and temperature tolerant microalga capable of sequestering CO2 from flue gas. Microalga strain SA1 was isolated from a freshwater body of Assam and identified as Scenedesmus obliquus (KC733762). At 13.8±1.5% CO2 and 25 °C, maximum biomass (4.975±0.003 g L(-1)) and maximum CO2 fixation rate (252.883±0.361 mg L(-1) d(-1)) were obtained which were higher than most of the relevant studies. At elevated temperature (40 °C) and 13.8±1.5% CO2 maximum biomass (0.883±0.001 g L(-1)) was obtained. The carbohydrate, protein, lipid, and chlorophyll content of the CO2 treated SA1 were 30.87±0.64%, 9.48±1.65%, 33.04±0.46% and 6.03±0.19% respectively, which were higher than previous reports. Thus, SA1 could prove to be a potential candidate for CO2 sequestration from flue gas as well as for the production of value added substances.

Novel pore-expanded MCM-41 for CO2 capture: synthesis and characterization.

Recently, amine-functionalized mesoporous silica materials have attracted considerable attention as a promising chemical sorbent for postcombustion CO2 capture applications. However, the grafting of amines in the conventional MCM-41 support induces the subsequent reduction of surface area and pore volume of the sorbents, affecting the CO2 adsorption-desorption kinetics significantly. To mitigate this problem, expensive pore expansion agents have been used to increase the pore size as well as the pore volume. The present study provides an innovative approach to the development of novel pore-expanded MCM-41 without the application of any swelling agent. The average pore size (~30 nm) obtained in our work is remarkably higher than the values (9 to 10 nm) reported in the literature. On the basis of the fundamental understanding of micelle properties under different alkaline conditions, a mechanism for the pore expansion process is proposed. The outcome (1.2 mmol/g) of the preliminary CO2 adsorption studies carried out on the novel support material grafted with monoamine silane is very promising.

Phenol degradation by Bacillus cereus: pathway and kinetic modeling.

The microbial degradation of phenol by pure cultures Bacillus cereus MTCC 9817 strain AKG1 and B. cereus MTCC 9818 strain AKG2 is studied in batch mode for several initial concentrations of phenol in the range of 100-2000 mg/L with an interval of 100mg/L. Degradation pathways are investigated at initial phenol concentrations of 100, 500, 1000, 1500, and 2000 mg/L. The bacteria are able to degrade phenol of concentration as high as 2000 mg/L. The maximum degradation rate is obtained at an initial phenol concentration of about 800 mg/L for the strain AKG1 and about 200mg/L for the strain AKG2. Both the strains degrade phenol via meta-cleavage pathway through formation of 2-hydroxymuconic semialdehyde (2-HMSA) as an intermediate product. Modeling of the biodegradation of phenol indicates that the Haldane inhibitory model predicts the experimental data fairly well for both the strains.

Temperature-dependent pyrolytic product evolution profile for low-density polyethylene from gas chromatographic study.

In this work, a product distribution study from thermal degradation of low-density polyethylene (LDPE) is presented. Thermal degradation of the polymer was investigated under dynamic condition in an inert environment using a thermo-gravimetric analyzer (TGA) coupled with evolved products' analysis using a gas chromatograph (GC). Fractions evolved at nine different temperatures from 200 to 600 degrees C were injected into GC for a detailed product analysis. The main objective of the present investigation is to highlight the species-specific evolution profiles of LDPE pyrolyzates (C5-C44) at different stages of its degradation under an inert environment. Pyrograms have been analyzed in terms of amount of different products evolved at various pyrolysis temperatures. Volatile pyrolyzates essentially remain low at low decomposition temperature (200-300 degrees C) of the polymer, which gradually increase to attain a maximum at maximum decomposition temperature (470 degrees C) and finally level off at 600 degrees C. In the mechanistic approach adopted to understand the decomposition mechanism of LDPE, the following reaction types were considered: (a) main chain cleavage to form chain-terminus radicals; (b) intramolecular hydrogen transfer to generate internal radicals; (c) intermolecular hydrogen transfer to form both volatile products and radicals; and (d) beta-scission to form both volatiles and terminally unsaturated polymer.

Isolation and characterization of hyper phenol tolerant Bacillus sp. from oil refinery and exploration sites.

Bacillus cereus MTCC 9817 strain AKG1 and B. cereus MTCC 9818 strain AKG2 were isolated from petroleum refinery and oil exploration site, respectively. The 16S rDNA sequence of strain AKG1 showed the closest relation to B. cereus 99.63% and Bacillus coagulans 99.63% followed by 99.34% homology with Bacillus thuringiensis strain 2PR56-10. AKG2 is mostly related to B. thuringiensis strain CMG 861 with 99.37% homology. The similarity search between AKG1 and AKG2 gave the lowest similarity 99.19% among same genus similar sequences. At phenol concentration of 1000 mg/L, the optimum growth conditions for AKG1 were found to be 37 degrees C and pH 7.0 and the same were found to be 37 degrees C and pH 7.5 for AKG2. The growth kinetics of the strains AKG1 and AKG2 are best fitted by Yano model (maximum growth rate, mu(max)=1.024 h(-1) and inhibition constant, K(I)=171,800 mg/L) and Edward model (mu(max)=0.5969 h(-1) and K(I)=1483 mg/L) respectively. Growth kinetics of both the strains are also well fitted by the Haldane model with mu(max)=0.4396 h(-1) and K(I)=637.8 mg/L for AKG1 and mu(max)=0.9332 h(-1) and K(I)=494.4 mg/L for AKG2.