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This study compared the effectiveness of different biosorbents, viz. materials commonly present in natural treatment systems (Scenedesmus quadricauda and reed) and commonly produced fruit wastes (orange and banana peel) to remove Cr(III) and Cr(VI) from a synthetic wastewater simulating tannery wastewater. The Cr(III) removal efficiency followed the order S. quadricauda>orange peel>banana peel>reed, whereas the Cr(VI) removal followed the order banana peel>S. quadricauda>reed>orange peel. The chromium biosorption kinetics were governed by the intraparticle diffusion mechanism. Isotherm data obtained using the different biosorbents were fitted to the Langmuir, Freundlich, and SIPS models, revealing that the experimental data followed most closely the monolayer sorption theory-based Langmuir model than the other models. The maximum Cr(III) sorption capacity, calculated using the Langmuir model, was found to be 12 and 9 mg/g for S. quadricauda and orange peel, respectively, and the maximum Cr(VI) sorption capacity calculated for banana peel was 3 mg/g. The influence of biosorbent size, pH, solid-liquid ratio, and competing ions were examined for Cr(III) biosorption by S. quadricauda and orange peel and for Cr(VI) sorption by banana peel. The solution pH was found to be the most influential parameter affecting the biosorption process: whereas pH 5 was found to be optimum for maximum removal of Cr(III), Cr(VI) was best removed at a pH as low as 3. Interference to chromium sorption by various ions revealed that Cr(III) binding onto orange peel occurs through electrostatic forces, whereas Cr(VI) binding onto banana peel through non-electrostatic forces.

The white rot fungus Phanerochaete chrysosporium has been identified to be an environmentally useful microorganism for the degradation of various hazardous pollutants, mainly because of its ligninolytic enzyme system, particularly the lignin peroxidase (LiP) secreted by the fungus. In the present work, the behavior of the fungus in liquid medium due to variation in physico-chemical parameters, i.e., glucose concentration, nitrogen concentration, agitation, etc., was studied. Increment of the initial concentration of glucose in the medium increases the biomass growth and LiP activity, when cultured under controlled conditions. The biomass growth and LiP activity by the fungus was modeled following stochastic approach. The behavior of growth and enzyme activity of the fungus observed from the model were found to be in agreement with the experiments qualitatively.

This work investigated the separation of polyhydroxybutyrate (PHB) containing Ralstonia eutropha cells from the culture broth using a novel ceramic based tubular membrane assembly. The culture broth was fed into outer surface of the membrane (shell side) and permeate was drawn from the tube side. Further, the number of ceramic membranes in the assembly was raised from 1 to 4 and its performance was assessed by measuring the broth flux, biomass and PHB recovery as a function of applied pressure (49 kPa -196 kPa). The present ceramic membrane is found to be highly efficient (99.9 ± 0.03%) in recovering the PHB from the culture broth. A maximum initial water flux of 444L m-2 h-1 and a permeate broth flux of 52 L m-2 h-1 was observed at the maximum applied pressure (196 kPa) and with four number of ceramic membranes added to the membrane assembly. Both biomass and PHB recovery were observed to decrease with an increase in the applied pressure; on the contrary, a reduction in the applied pressure enhanced the biomass and PHB recovery, but at the cost of low broth flux. However, this relationship is overcome by increasing the number of membranes in the membrane assembly. [ABSTRACT FROM AUTHOR]

Abstract Marine sources especially crustaceans have been extensively used worldwide for the production of chitosan. However, limited availability as well as variations in the properties of the derived chitosan is a serious drawback of utilizing marine sources for chitosan production. This study investigated sustainable and green approach of fungal chitosan production using paper mill wastewater as a cheap and easily available substrate. The fungus Penicillium citrinum IITG_KP1 used in this study was initially isolated from an infected bamboo shoot. Addition of acetic acid at low levels led to a 150% increase in the yield of chitosan from 95 g/kg to 138 g/kg of dry fungal biomass. This result correlated well with an increase in xylose uptake rate due to acetic acid addition that was confirmed by enhanced activity of xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes in the presence of acetic acid. Very high COD removal efficiency (75%) along with 70% phenolic reduction and 84% decolourization efficiency of the raw paper mill wastewater without any prior pre-treatment was further achieved by carrying out the fungal fermentation using a bioreactor under batch mode of operation. The fungal chitosan showed properties comparable with those of a commercially available standard. Graphical abstract Image 1059 Highlights • Acetic acid induced chitosan production by P. citrinum biomass. • A novel method of fungal chitosan production using industrial wastewater is reported. • Batch mode of bioreactor operation is highly efficient for wastewater COD removal and chitosan production. • The fungal chitosan produced has properties comparable with those of the commercially available standards. [ABSTRACT FROM AUTHOR]

This study investigated simultaneous heavy metals removal and anthracene biodegradation by Rhodococcus opacus at different initial anthracene concentrations in the range 50-200 mg L. The heavy metals tested were Fe(III), Cu(II), Zn(II), Cd(II), Ni(II), and Pb(II) at 10 mg L initial concentration: The organism was found to be well capable of removing the heavy metals along with high anthracene biodegradation efficiency. However, anthracene biodegradation rate by the organism was reduced due to these heavy metals. In addition, the heavy metals effect on R. opacus biomass growth followed the order: Cd > Ni > Pb > Cu > Zn > Fe. The total time to anthracene biodegradation increased from 144 to 216 h in the presence of Fe, Zn, Cu, or Pb, and it was up to 240 h in the presence of Cd or Ni. Compared with 70.2% (w/w) lipid accumulation by the bacterium in the absence of these heavy metals, a significant decline in the same was observed in the presence of the different heavy metals. These values were 41.2, 44.1, 52.1, 54.1, 58.6, and 63.1% (w/w) for Cd, Ni, Pb, Cu, Zn, and Fe, respectively. Field emission scanning electron microscopy integrated with energy dispersive X-ray spectroscopy and transmission electron microscopy of the biomass grown in the presence and absence of these heavy metals further confirmed a change in morphology of the bacterium due to the heavy metals. Fourier transmission infrared spectroscopy spectra of the biomass obtained during its growth in the presence and absence of the heavy metals confirmed the involvement of N-H, C-H bend, -CH-(C=O), C-N stretch, C-H and O-H bending, and -C-Cl groups on the biomass for heavy metal uptake by the bacterium. [ABSTRACT FROM AUTHOR]

Biological sulfate reduction is an alternative and emerging technique to treat metal containing sulfate-rich wastewater. In this study, the potential of anaerobic biomass from three different wastewater treating systems was evaluated for heavy metal removal under sulfate-reducing conditions. Among the three different biomass sources tested in the study, the biomass from a lab-scale upflow anaerobicpacked bed reactor (UFAR) showed maximum sulfate reduction (>90%) within 96 h with a maximum wastewater chemical oxygen demand (COD) removal of up to 92.8%. The heavy metal removal efficacy was in the order Cu > Fe > Ni > Pb > Cd > Zn. Metal removal by the biomass was further established due to its precipitation with sulfide formed by the sulfate-reducing bacteria. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) of the metal-loaded biomass showed that the precipitates formed during the process consist of mainly the metal sulfides. The transmission electron microscopy (TEM) along with energy dispersive spectroscopy (EDS) confirmed that the metal precipitates were confined to the exterior and interior surface of the bacterial cells. The Fourier transmission infrared spectroscopy (FTIR) spectra of the biomass, obtained during its growth, clearly established the presence of sulfate ions. [ABSTRACT FROM AUTHOR]

As(III) removal from dilute aqueous solutions by biosorption onto pellets of the white rot fungusPhanerochaete chrysosporiumwas investigated. The As(III) uptake capacity was evaluated at low initial concentrations (0.2–1 mg/L) which revealed that theP. chrysosporiumpellets were only slightly less efficient than the well studied adsorbent granular ferric hydroxide. Moreover, its performance was much more superior compared to anaerobic granular sludge, another cheaply available bacterial biosorbent. In the studied pH (5–9) and biomass concentration (0.25–1.5 g/L wet weight basis) ranges, no large differences in As(III) removal efficiency were observed. The influence of different ions, commonly present in groundwater, such as nitrate, fluoride, chloride, and Fe(III) on As(III) removal by the fungus was also examined by performing experiments as per the statistically valid two-level fractional factorial design of experiments. This showed a very good removal of only As(III) and Fe(III) (maximum 100%), the removal of the other ions in the mixture was very poor with the least well adsorbed being fluoride. A desorption efficiency exceeding 95% of the bound As(III) from the fungal biomass was achieved using sodium hydroxide (0.05–0.1 M) as desorbent. [ABSTRACT FROM PUBLISHER]

laboratory-scale rotating biological contactor (RBC) reactor with immobilized fungal biomass of Phanerochaete chrysosporium was investigated for its performance in decolourizing synthetic wastewater containing single or mixture of azo dyes, Direct Red-80 (DR-80) and Mordant Blue-9 (MB-9). Decolourization efficiency in the continuously operated bioreactor was studied by varying dye inlet concentration and disc rotation speed at two different wastewater hydraulic retention times (HRTs), i.e. 24and 48 h. Results from the single dye-containing experiments showed that the system could completely decolourize the wastewater for a maximum inlet dye concentration within the range 25-200 mg L and 48 h HRT in the reactor; for an inlet dye concentration above 200 mg L, the decolourization efficiency slightly reduced up to 85% for the same HRT. However, wastewater containing DR-80 was found to be decolourized more efficiently compared to that containing MB-9. Further, the effect of increase in the disc rotation speed from 2 to 6 rpm in the study revealed no large differences in the decolourization efficiencies of the wastewaters. Similar results were obtained with wastewater containing the dyes together at various concentration combinations as per the two-level factorial design of experiments. Enzyme activities of lignin peroxidase and manganese peroxidase by the fungus were also analysed in the study, and the results indicated that while DR-80 showed a large negative effect on both the enzymes, MB-9 affected mainly the MnP activity by the fungus. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cellulosimicrobium funkei efficiently utilized DMP and DEP as single and dual substrates. • This is the first study on DMP and DEP biodegradation in a continuous stirred tank bioreactor. • DMP biodegradation rate is higher than that of DEP due to its short chain length. • DMP and DEP biodegradation follows a similar biochemical pathway via phthalic acid formation. • DMP at a high concentration enhances DEP degradation in mixture. This study investigated the potential of Cellulosimicrobium funkei for degrading dimethyl phthalate (DMP) and diethyl phthalate (DEP). Effect of different initial concentrations of phthalates on their biodegradation and growth of C. funkei was examined using shake flasks and a continuous stirred tank reactor (CSTR). Complete degradation of both DMP and DEP was achieved in CSTR, even up to 3000 and 2000 mg/L initial concentrations, respectively. Simultaneous degradation of the phthalates in mixture, i.e. more than 80% and 55% biodegradation efficiency were achieved at 1000 and 2000 mg/L initial concentrations of DMP and DEP, respectively, using the CSTR. Mass balance analysis of the degradation results suggested proficient degradation of DMP and DEP with biomass yield values of 0.64 and 0.712, respectively. The high values of inhibition constant Ki estimated using the Tessier and Edward substrate inhibition models indicated very good tolerance of C. funkei toward biodegradation of DMP and DEP. [ABSTRACT FROM AUTHOR]

This study evaluated the kinetics of biomass growth, biohydrogen production and substrate utilization using carbon monoxide as the sole carbon and energy source. Experiments were conducted at different initial CO concentration in the range 1.8–5.12 mmol/L over a period of 144 h in order to assess the effect of CO concentration on biomass growth, substrate utilization and H 2 production. Complete utilization (100%) of CO was achieved up to an initial concentration of 3.8 mmol/L and it gradually decreased to 84.5% for 4.4 mmol/L and 83.7% for 5.12 mmol/L. The experimental results of CO utilization were fitted to substrate utilization kinetic models reported in the literature, and it followed a modified Gompertz model. A maximum yield of H 2 on CO was found to be 70.8% and a maximum H 2 production of 29.9 mmol/L was obtained for an initial CO concentration of 5.12 mmol/L. The experimental results on biohydrogen production matched well with the values predicted using the modified Gompertz model. Furthermore, the experimental data on specific growth rate of the ananerobic biomass at different H 2 concentration was fitted to different product inhibition models and the best fit was obtained with Aiba model. This study showed product inhibition on both specific growth rate of biomass and H 2 production due to H 2 accumulation in the gas phase. A very good correlation between the experimental specific growth rate and the Han-Levenspiel model predicted values were obtained with a high determination coefficient (R2) value of more than 0.96. Image 1 • Kinetics of biohydrogen production from carbon monoxide (CO) is reported. • More than 80% of CO was utilized for biohydrogen production. • CO utilization decreased at high CO concentration without affecting H 2 production. • H 2 at a high concentration is inhibitory to both H 2 production and biomass growth. [ABSTRACT FROM AUTHOR]

This study investigated the Cu(II) removal by Nostoc muscorum, a cyanobacterium isolated from a toxic metal polluted site in Meghalaya, using a batch photobioreactor with an aim to elucidate the removal mechanism and its effect on nitrate uptake by the cyanobacterium. Experiments were carried out using a batch photobioreactor by varying the initial Cu(II) concentration in the range of 5–30 mg L −1 . Results obtained in this study showed that a maximum of 5.628 ± 0.05 g L −1 of biomass concentration could be obtained in the absence of Cu(II), whereas this value of biomass reduces to 4.3 ± 0.0057 g L −1 in presence of 5 mg L −1 of initial Cu(II) concentration, which further reduces to 2.51 ± 0.01 g L −1 for an initial Cu(II) concentration of 30 mg L −1 . Besides, an increase in the initial Cu(II) concentration delayed the uptake of nitrate by the cyanobacterium. However, complete removal of Cu(II) was observed for all the four different initial Cu(II) concentration. The estimated value of nitrate uptake rate in the absence of Cu(II) was found to be 0.115 mg L −1 d −1 , which was reduced to 0.029 mg L −1 d −1 due to 30 mg L −1 initial Cu(II) concentration in the medium. The experimental nitrate uptake rate values were fitted to three unstructured kinetic models reported in the literature for estimating the biokinetic constants. Among the three models, Han-levenspiel and Andrew models fitted the experimental data closely with a determination coefficient (R 2 ) value of 0.942 and 0.921, respectively. The critical Cu(II) concentration obtained as per the Han-levenspiel model was found to be 0.0325 g L −1 . [ABSTRACT FROM AUTHOR]

Sulfate reduction by carbon monoxide (CO) utilizing anaerobic biomass from a large scale upflow anaerobic sludge blanket reactor was studied. Anaerobic mixed microbial consortia from five different sources were initially examined for their biological CO conversion potential. Among the different biomass, the biomass from an upflow anaerobic sludge blanket reactor treating domestic wastewater, located in Kavoor, Karnataka, India, showed a maximum CO conversion efficiency. The effect of three main culture parameters, i.e. inoculum volume, initial CO concentration and temperature on simultaneous CO conversion and sulfate reduction was assessed employing the Taguchi experimental design technique. A maximum CO conversion of 85.62% and a maximum sulfate reduction of 50.65% were achieved. Furthermore, the experimental data was fitted to substrate inhibition models reported in the literature. Among the different models, Monods and Haldane kinetic models were found most suitable to describe the kinetics of biomass growth and CO removal by the anaerobic biomass. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs), including naphthalene, phenanthrene and fluoranthene are commonly found in wastewaters from refineries and biomass gasification industries. This study investigated the simultaneous biodegradation of these PAHs along with lipid accumulation by Rhodococcus opacus in a ternary substrate system. A 2 3 full factorial design of experiments was employed with the three PAHs at two different levels by varying their initial concentrations in the range 50–200 mg L −1 each. A maximum removal of 91.6%, 82.3% and 80.7% was achieved for naphthalene, phenanthrene and fluoranthene, respectively. The individual effect of PAH concentration was found to be more significant than 2-way and 3-way interaction effects on their degradation. PAH biodegradation efficiency in the mixture was mainly affected by initial concentration and aromatic complexity of the PAHs. Identification of the PAH degradation metabolites was carried out using LC-MS analysis, which clearly revealed that the PAHs were degraded primarily via the ortho/para pathway. This study demonstrates the potential utility of R. opacus for bioremediation and industrial wastewater treatment. [ABSTRACT FROM AUTHOR]