Biodegradation of naphthalene by biocatalysts isolated from the contaminated environment under optimal conditions.

Polycyclic aromatic hydrocarbons (PAHs) pollution occurs in freshwater and marine environment by anthropogenic activities. Moreover, analysis of the PAHs-degradation by the indigenous bacterial strains is limited, compared with other degraders. In this study, naphthalene (NAP) biodegrading bacteria were screened by enrichment culture method. Three bacterial strains were obtained for NAP degradation and identified as Bacillus cereus CK1, Pseudomonas aeruginosa KD4 and Enterobacter aerogenes SR6. The amount of hydrogen, carbon, sulphur and nitrogen of wastewater were analyzed. Total bacterial count increased at increasing incubation time (6-60 days) and moderately decreased at higher NAP concentrations. The bacterial population increased after 48 days at 250 ppm NAP (519 ± 15.3 MPM/mL) concentration and this level increased at 500 ppm NAP concentration (541 ± 12.5 MPM/mL). NAP was degraded by bacterial consortium within 36 h-99% at 30 °C. PAHs degrading bacteria were grown optimally at 4% inoculum concentrations. Bacterial consortium was able to degrade 98% NAP at pH 7.0 after 36 h incubation and degradation potential was improved (100%) after 34 h (pH 8.0). Also at pH 9.0, 100% biodegradation was registered after 36 h incubation. When the agitation speed enhanced from 50 ppm to 150 ppm, increased bacteria growth and increased NAP degradation within 42 h incubation. Among the nutrient sources, beef extract, peptone and glucose supplemented medium supported complete degradation of PAHs within 30 h, whereas peptone supported 94.3% degradation at this time. Glucose supplemented medium showed only 2.8% NAP degradation after 6 h incubation and reached maximum (100%) within 42 h incubation. Bacterial consortium can be used to reduce NAP under optimal process conditions and this method can be used for the removal of various hydrocarbon-compounds.

Adsorption of heavy metals from the aqueous solution using activated biomass from Ulva flexuosa.

The removal of various highly toxic heavy metals from wastewater environment is an important task to improve environment. The biosorption potential of cadmium, cobalt and zinc was evaluated using Ulva flexuosa biomass. The impacts of adsorbent dosage, pH of the medium, contact time, and agitation speed were analyzed. The maximum biosorption potential was reached at pH 4.0, 0.4 g initial biosorbent dosage, contact time 40 min and 30 mg/L initial metal concentration for cadmium, while the other factors were similar to zinc, except 35 min contact time (p < 0.01). The optimum absorption was pH 4, 0.6% adsorbent dosage, after 30 min contact time with the heavy metals and 40 mg/L cobalt concentration. Heavy metal removal efficiency was 94.8 ± 3.3%, 87.5 ± 2.3%, and 90.8 ± 1.4%, for cadmium, cobalt, and zinc, respectively (p < 0.01). The Langmuir constant (R2) was 0.980 for cadmium, 0.838 for cobalt and it was 0.718 for zinc. The present results revealed that the selected acid modified biomass was highly suitable for the adsorption of metal ions such as, Cd2+, Co2+ and Zn2+. The present work revealed the potential application of algal biomass for the removal of various heavy metals from the environment.

Functionalization of gold nanoparticles by ß-cyclodextrin as a probe for the detection of heavy metals in water and photocatalytic degradation of textile dye.

Gold nanoparticles (AuNPs) and AuNPs functionalized by ß-cyclodextrin (ß-CD/AuNPs) were prepared successfully through chemical reduction method. The structural, morphological, optical, compositional and vibrational studies for the AuNPs and ß-CD/AuNPs were carried out. Functionalization of AuNPs by ß-CD was confirmed with FT-IR results. The UV-visible absorption spectra exhibit a red-shift with decreasing average particle size. This sustains the enhancement in surface area (SA) to volume (V) ratio that is one of the peculiar characteristics of nanoparticles. TEM results show that ß-CD/AuNPs formed were monodispersed and self assembled. Also it shows a decrease in average particle size and improved distribution. The use of ß-CD in the synthesis of AuNPs are revealed not only create uniform small sized nanoparticles but these water soluble nanoparticles have very good antibacterial action by inhibiting the growth of bacteria commonly found in water and sensing activity for sensing the concentration of toxic metals in water. The sensitivity of the system towards copper (Cu) concentration was found as 1.788/mM for ß-CD/AuNPs and 1.333/mM for AuNPs. The photocatalytic action of the obtained nanoparticles increases with decreasing average particle size. The kapp value of this photocatalytic degradation of textile dyeing waste water in presence of AuNPs was 0.002/min and ß-CD/AuNPs was 0.005/min. This is a non-toxic and eco-friendly approach.