Search

The study employed batch shake flasks to evaluate the impact of various nitrogen sources, phosphate levels, and sodium acetate (Na-acetate) on the Rhodotorula mucilaginosa growth and metabolite production. Adding Na-acetate to the medium resulted in significant improvements in critical metabolites. In shake flask experiments, this led to a cell dry weight (CDW) of 1.65 ± 0.94 g L -1 , with lipids comprising 66.53% of the biomass. While β-carotene and carotenoid were 5.84 ± 0.05 and 37.66 ± 2.13 µg g -1 , respectively. Subsequent experiments in a batch reactor with Na-acetate supplementation further improved these metrics. CDW increased to 5.02 ± 0.83 g L -1 , and lipid content to 65.73 ± 0.81%. Carotenoid production rose to 40.33 ± 1.84 µg g -1 , with β-carotene reaching 17.63 ± 0.32 µg g -1 . The most promising results were obtained using a fed-batch bioreactor strategy with Na-acetate. R. mucilaginosa achieved the highest yields across all parameters: 48.36 ± 1.14 µg g -1 of total carotenoids, 21.38 ± 1.14 µg g -1 of β-carotene, and a lipid content of 68.58 ± 1.95%.

Fossil fuel use drives greenhouse gas emissions and climate change, highlighting the need for alternatives like biomass-derived syngas. Syngas, mainly H 2 and CO, is produced via biomass gasification and offers a solution to environmental challenges. Syngas fermentation through the Wood-Ljungdahl pathway yields valuable chemicals under mild conditions. However, challenges in scaling up persist due to issues like unpredictable syngas composition and microbial fermentation contamination. This review covers advancements in genetic tools and metabolic engineering to expand product range, highlighting crucial enabling technologies that expedite strain development for acetogens and other non-model organisms. This review paper provides an in-depth exploration of syngas fermentation, covering microorganisms, gas composition effects, separation techniques, techno economic analysis, and commercialization efforts., Competing Interests: Declaration of interests The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study explored the impact of sodium acetate (Na-acetate) impact on lipid, carotenoid, and β-carotene production by the newly isolated strain Rhodotorula mucilaginosa . Batch and fed-batch bioreactor cultures were employed to optimize growth conditions and product yields. R. mucilaginosa fed with Na-acetate in the yeast medium was evaluated in the batch bioreactor culture. The following merits were accomplished for the cell dry weight (5.02 gL -1 ), lipid content (65.73%), carotenoid (40.33 µgg -1 ) and β-carotene (17.63 µgg -1 ) consistently. The fed-batch reactor cultivation using yeast extract supplemented with Na-acetate yielded superior lipid content (68.58%), cell dry weight (5.92 gL -1 ), carotenoid (48.36 µgg -1 ), and β-carotene production (21.38 µgg -1 ) compared to batch cultivation. The fatty acid methyl esters (FAMEs) are produced from the lipids suitable for biodiesel production. These findings highlight the potential of R. mucilaginosa as a promising organism for sustainable biofuel and high-value compound production. Further optimization of culture conditions and downstream processing could enhance the commercial viability of this approach.

The non-linear complex relationships among the process variables in wastewater and waste gas treatment systems possess a significant challenge for real-time systems modelling. Data driven artificial intelligence (AI) tools are increasingly being adopted to predict the process performance, cost-effective process monitoring, and the control of different waste treatment systems, including those involving resource recovery. This review presents an in-depth analysis of the applications of emerging AI tools in physico-chemical and biological processes for the treatment of air pollutants, water and wastewater, and resource recovery processes. Additionally, the successful implementation of AI-controlled wastewater and waste gas treatment systems, along with real-time monitoring at the industrial scale are discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The biodegradability of poly (3-hydroxybutyrate) (PHB)-based food packaging material PHB/5GS/0.7MgO, developed by incorporating 5 wt% grapeseed oil (GS) and 0.7 wt% MgO nanoparticles using solution casting route, was investigated in soil and river water environments. For comparison, the biodegradability of neat PHB films and PHB-based films loaded only with 5 wt% GS (PHB/5GS) was also studied. Remarkably, all PHB-based films showed 100 % weight loss in soil within 25 days. In contrast, the weight loss of PHB, PHB/5GS, and PHB/5GS/MgO films in river water was 27, 24, and 20 %, respectively, in 120 days. Gradual reduction in average molecular weight and carbonyl index, alongside an increase in crystallinity, opacity, and the number of chain scissions per unit mass, was observed for various PHB-based films during their degradation in soil and river water. Overall, this study demonstrated high degradation efficiency of PHB-based food packaging material in soil than in river water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Production of value-added products from waste anaerobic digestate is economically and environmentally important for sustainable development of industrial process and products. In this study halophilic microalgae, Chlorella vulgaris 92001, Chlorella vulgaris 50291, Chlorella vulgaris 10241 and Tetraselmis indica, were initially screened for lutein production using synthetic dairy digestate (DD), municipal digestate (MD) and poultry digestate (PD) as no-cost substrates. Screening and optimization of parameters, such as dilution, pH, MgCl 2 , NaCl, NaHCO 3 and inoculum concentration for maximum lutein production were further performed employing statistically designed Plackett-Burman and response surface methodology. Cultivation of C. vulgaris 92001 in a split column photobioreactor under optimum culture condition showed increase in lutein production by 2.36-fold in batch mode. The influence of different hydraulic retention time (HRT) values of 150, 130, 100 and 90 h on lutein production was evaluated in continuous mode with the split column photobioreactor. Lutein produced using the synthetic poultry digestate showed good potential biopesticide activity against Spodoptera litura (fall armyworm). Overall, this study demonstrated bioprocess development to produce lutein using synthetic anaerobic digestate from marine algae and its potential application as a biopesticide., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Poly (3-hydroxybutyrate) (PHB) is undoubtedly a potential substitute for petroleum-based non-biodegradable food packaging materials due to its renewability, high crystallinity, biocompatibility, and biodegradability. Nonetheless, PHB exhibits certain shortcomings, including low flexibility, moderate gas barrier properties, and negligible antimicrobial and antioxidant activities, which limit its direct application in food packaging. Loading essential oils can increase flexibility and induce antimicrobial and antioxidant activities in biopolymers but at the cost of reduced tensile strength. In contrast, nanofiller reinforcement can increase the tensile strength and barrier properties of such biopolymers. Therefore, to harness the synergistic effects of essential oil and nanofiller, PHB-based films incorporated with 5 wt% grapeseed oil (GS) and varying concentrations (0.1-1 wt%) of MgO nanoparticles (MgO NPs) were prepared in this study following simple sonication-assisted solution casting technique. Physicochemical, tensile, microstructural, optical, barrier, antimicrobial, and antioxidant properties were then evaluated for the prepared composite films. FESEM analysis of the PHB-based films with 5 wt% GS and 0.7 wt% MgO NPs (PHB/5GS/0.7MgO) confirmed its compact morphology without any aggregates, pores, or phase separation. In comparison with pristine PHB, the PHB/5GS/0.7MgO films demonstrated higher tensile strength (by 1.4-fold) and flexibility (by 30-fold), along with 79 and 90 % reduction in water vapor and oxygen transmission, respectively. In addition, PHB/5GS/0.7MgO showed good UV-blocking properties, 65.25 ± 0.98 % antioxidant activity, and completely inhibited the growth of Staphylococcus aureus and Escherichia coli. Moreover, PHB/5GS/0.7MgO films proved beneficial effects in terms of extending the shelf-life of white button mushrooms up to 6 days at ambient room conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A continuous stirred tank bioreactor (CSTB) with cell recycling combined with ceramic membrane technology and inoculated with Rhodococcus opacus PD630 was employed to treat petroleum refinery wastewater for simultaneous chemical oxygen demand (COD) removal and lipid production from the retentate obtained during wastewater treatment. In the present study, the COD removal efficiency (COD RE ) (%) and lipid concentration (g/L) were predicted using two artificial intelligence models, i.e., an artificial neural network (ANN) and a neuro-fuzzy neural network (NF-NN) with a network topology of 6-25-2 being the best for NF-NN. The results revealed the superiority of NF-NN over ANN in terms of determination coefficient (R 2 ), root mean square error (RMSE), and mean absolute percentage error (MAPE). Three learning algorithms were tested with NF-NN; among them, the Bayesian regularization backpropagation (BR-BP) outperformed others. The sensitivity analysis revealed that, if solid retention time and biomass concentrations were maintained between 35 and 75 h and 3.0 g/L and 3.5 g/L, respectively, high COD RE (93%) and lipid concentration (2.8 g/L) could be obtained consistently., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Endocrine-disrupting phthalates (EDPs) are widely used as plasticizers for the manufacture of different plastics and polyvinyl chloride by providing flexibility and mechanical strength. On the other hand, they are categorized under priority pollutants list due to their threat to human health and the environment. This study examined biodegradation of a mixture of dimethyl, diethyl, dibutyl, benzyl butyl, di-2-ethylhexyl, and di-n-octyl phthalates using a CSTB (continuous stirred tank bioreactor) operated under batch, fed-batch, continuous, and continuous with biomass recycle operation modes. For operating the CSTB under biomass recycle mode, microfiltration using an indigenous tubular ceramic membrane was employed. Ecotoxicity assessment of the treated water was carried out to evaluate the toxicity removal efficiency by the integrated bioreactor system. From the batch experiments, the EDPs cumulative degradation values were 90 and 75% at 1250 and 1500 mg/L total initial concentration of the mixture, respectively, whereas complete degradation was achieved at 750 mg/L. In the fed-batch study, 93% degradation was achieved at 1500 mg/L total initial concentration of the mixture. In continuous operation mode, 94 and 85% degradation efficiency values were achieved at 43.72 and 52.08 mg/L⋅h inlet loading rate of phthalate mixture. However, continuous feeding with 100% biomass recycle revealed complete degradation at 41.67 mg/L⋅h inlet loading rate within the 84 h operation period. High seed germination index and low mortality percentage of brine shrimps observed with phthalate degraded water from the integrated bioreactor system revealed its excellent potential in the treatment and toxicity removal of phthalates contaminated environment., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Phthalic acid esters (PAEs) are highly toxic compounds and can disrupt the hormonal balance of human, animal, and aquatic organisms. Due to the hazardous nature of such compounds, their removal from constituent wastewater before discharging into the environment is mandatory. This study focused on the biodegradation of dimethyl phthalates (DMP), di-n-butyl phthalates (DBP), and di-n-octyl phthalates (DnOP) by Gordonia sp. in a batch system. Initially, five different concentrations of DBP, DMP, and DnOP (200-1000 mg/L) were chosen individually as the sole carbon source to examine their effect on the biodegradation and biomass growth of Gordonia sp. Complete degradation of DBP and DMP was achieved up to 1000 mg/L initial concentration within 96 h, whereas in case of DnOP, the degradation value was only 83.5% at 120 h for the same initial concentration. The experimental data were fitted into various substrate inhibition kinetic models, and accurate predicted values of degradation of all the three PAEs were obtained using the Tiesser model in comparison with other models, which yielded the highest and lowest R 2 and SSE values of 0.99 and 0.02 × 10 -4 , respectively. In addition, the phytotoxicity of PAEs degraded samples was assessed and more than 50% germination index value was observed for DMP and DBP degraded sample which established the treatment efficiency of Gordonia sp. in degrading DMP and DBP. Hence, high DMP and DEP degradation and phytotoxicity removal efficiency of Gordonia sp. demonstrate its potential for the treatment of PAEs contaminated wastewater.

Poly (3-hydroxybutyrate) (PHB) is a bio-based biodegradable biopolymer with excellent potential to substitute petrochemical-based food packaging materials. Nevertheless, low elongation at break is one of the limiting factors for its commercial-scale application in the packaging field. Microbial contamination and lipid oxidation are the two main causes of food spoilage and pose huge challenges to the food industry. In this regard, essential oils are bioactive compounds that, in addition to providing antimicrobial and antioxidant properties, can improve the flexibility of biopolymers. Therefore, to overcome the aforementioned challenges, the current study aimed to fabricate novel PHB composite films loaded with essential oils, viz. grapeseed oil (GS), bergamot oil (BG), and ginger oil (GG), by a simple solution casting technique. To evaluate the potential of prepared PHB/essential oil composites for food packaging applications, extensive characterizations of their mechanical, structural, barrier, optical, and thermal properties were carried out. Interestingly, PHB/essential oil composites demonstrated good UV-blocking properties without affecting its transparency. PHB films loaded with 5 wt% GS showed a 30-fold enhancement in flexibility compared to pristine PHB. The DPPH radical scavenging activities of PHB/5GS, PHB/5BG, and PHB/5GG films are 53.17 ± 4.76, 50.70 ± 3.92 and 86.38 ± 2.73 %, respectively. The antibacterial activities of PHB/5GS, PHB/5BG, and PHB/5GG films against the model bacterium E. coli are 19.72 ± 0.97, 12.62 ± 2.23 and 29.98 ± 2.15 %, respectively, whereas, for S. aureus, the values are 61.56 ± 3.39, 30.28 ± 0.92 and 70.97 ± 0.26 %, respectively. Moreover, the overall migration values of the composite films in simulants representing hydrophilic, acidic, and lipophilic foods did not exceed the prescribed overall migration limit (10 mg/dm 2 )., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Metallic nanoparticles (NPs) find applications in many different industrial sectors. However, the fate of these NPs in the environment and their potential impact on organisms living in different ecosystems are not fully known. In this work, the individual effect of biogenic and chemically synthesized lead sulfide nanoparticles (PbSNPs) and cadmium sulfide nanoparticles (CdSNPs) on the activity of the oleaginous bacterium Rhodococcus opacus PD630 which belongs to an ecologically important genus Rhodococcus was investigated. A dose-dependent increase in PbSNPs and CdSNPs uptake by the bacterium was observed upto a maximum of 16.4 and 15.6 mg/g cell, corresponding to 98% and 95% uptake. In the case of chemically synthesized NPs, the specific PbSNPs and CdSNPs uptake were slightly less [15.5 and 14.8 mg/g cell], corresponding to 93.2% and 88.4% uptake. Both biogenic and chemically synthesized PbSNPs and CdSNPs did not affect the bacterial growth. On the other hand, the triacylglycerol (biodiesel) content in the bacterium increased from 30% to a maximum of 75% and 73% CDW due to oxidative stress induced by biogenic PbSNPs and CdSNPs. The results of induced oxidative stress by biogenic metal nanoparticle were similar to that induced by the chemically synthesized NPs., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

In this study, paper mill wastewater and hemicellulose hydrolysate were evaluated as low-cost substrates for fungal chitosan production using Penicillium citrinum . Submerged fermentation was first studied using a bioreactor operated under batch, fed-batch and continuous modes with paper mill wastewater as the substrate. Very high removal (91%) of organics as chemical oxygen demand (COD) in the wastewater with 160 mg L -1 chitosan production by P. citrinum was obtained using the bioreactor operated under fed-batch mode for 72 h. Moreover, 86% reduction of phenolics in the wastewater with 89% decolourization efficiency was achieved in the fed-batch experiments with the bioreactor. Under the continuous mode of operation with the bioreactor, maximum chitosan production of 170 mg L -1 was observed. The effect of acetic acid addition to the wastewater for enhancing chitosan production by the fungus was further studied in a batch system. Chitosan productivity of 2.33 mg L -1 h -1 was obtained with 50 mg/L acetic acid. Various models, viz . Monod, Haldane, Andrews, Webb and Yano, were fitted to the experimental data for understanding the kinetics involved in the process. Haldane model accurately fitted the experimental data on biomass specific growth rate, acetic acid consumption rate and chitosan production rate by P. citrinum with acetic acid addition to the wastewater. Fungal fermentation of another low-cost substrate, rice straw hydrolysate, was further studied using the batch-operated bioreactor; and a maximum chitosan titre of 911 mg L -1 was achieved using the detoxified rice straw hydrolysate. Highlights Low-cost substrates for chitosan production by Penicillium citrinum are reportedAcetic acid addition to paper mill wastewater enhances chitosan productionBiomass growth and chitosan production follow substrate inhibition kineticsFed-batch -operated bioreactor resulted in 91% wastewater treatment efficiencyMaximum chitosan titre of 911 mg L -1 was achieved with rice straw hydrolysate.

Selenite (Se 4+ ) is the most toxic of all the oxyanion forms of selenium. In this study, a feed forward back propagation (BP) based artificial neural network (ANN) model was developed for a fungal pelleted airlift bioreactor (ALR) system treating selenite-laden wastewater. The performance of the bioreactor, i.e., selenite removal efficiency (RE selenite ) (%) was predicted through two input parameters, namely, the influent selenite concentration (IC selenite ) (10 mg/L - 60 mg/L) and hydraulic retention time (HRT) (24 h - 72 h). After training and testing with 96 sets of data points using the Levenberg-Marquardt algorithm, a multi-layer perceptron model (2-10-1) was established. High values of the correlation coefficient (0.96 ≤ R ≤ 0.98), along with low root mean square error (1.72 ≤ RMSE ≤ 2.81) and mean absolute percentage error (1.67 ≤ MAPE ≤ 2.67), clearly demonstrate the accuracy of the ANN model (> 96%) when compared to the experimental data. To ensure an efficient and economically feasible operation of the ALR, the process parameters were optimized using the particle swarm optimization (PSO) algorithm coupled with the neural model. The RE selenite was maximized while minimizing the HRT for a preferably higher range of IC selenite . Thus, the most favourable optimum conditions were suggested as: IC selenite - 50.45 mg/L and HRT - 24 h, resulting in RE selenite of 69.4%. Overall, it can be inferred that ANN models can successfully substitute knowledge-based models to predict the RE selenite in an ALR, and the process parameters can be effectively optimized using PSO., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Cellulose, starch, chitosan, polylactic acid, and polyhydroxyalkanoates are seen as promising alternatives to conventional plastics in food packaging. However, the application of these biopolymers in the food packaging industry on a commercial scale is limited due to their poor performance and processing characteristics and high production cost. This review aims to provide an insight into the recent advances in research that address these limitations. Loading of nanofillers into polymer matrix could improve thermal, mechanical, and barrier properties of biopolymers. Blending of biopolymers also offers the possibility of acquiring newer materials with desired characteristics. However, nanofillers tend to agglomerate when loaded above an optimum level in the polymer matrix. This article throws light on different methods adopted by researchers to achieve uniform dispersion of nanofillers in bionanocomposites. Furthermore, different processing methods available for converting biopolymers into different packaging forms are discussed. In addition, the potential utilization of agricultural, brewery, and industrial wastes as feedstock for the production of biopolymers, and integrated biorefinery concept that not only keep the total production cost of biopolymers low but are also environment-friendly, are discussed. Finally, future research prospects in this field and the possible contribution of biopolymers to sustainable development are presented. This review will certainly be helpful to researchers working on sustainable food packaging, and companies exploring pilot projects to scale up biopolymer production for industrial applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A novel adsorbent based on metal sulfide nanoparticles (MeSNPs) was biologically synthesized from metallic wastewater and examined for azo dyes removal from aqueous solution in batch and continuous systems. The size of the MeSNPs was in the range of 8-10 nm, with an average specific surface area of 120.4 m 2 /g. Batch adsorption study was then carried out using Direct Red 80 (DR 80) and Mordant Blue 9 (MB 9) as the model azo dyes by varying MeSNPs dosage, contact time, pH, and initial dye concentration. More than 99% removal efficiency of both the dyes was achieved by using MeSNPs at the following optimum conditions: 200 mg dosage, pH 2, 6 min contact time, and 100 mg L -1 initial dye concentration. The batch sorption isotherm results were described using the Sips model, with the maximum predicted capacity values of 143.7 and 198.3 mg of dye per gram of adsorbent for DR 80 and MB 9, respectively. Besides, the sorption kinetic data for both the dyes followed the pseudo-second-order rate. Furthermore, maximum desorption efficiency values of 93% for DR 80 and 97% for MB 9 were achieved using an aqueous solution of pH 12, thus indicating that the adsorbent can be regenerated and reused further. Dynamic adsorption of the dyes was studied using a fixed-bed column with the MeSNPs as a function of liquid flow rates. The results showed an increase in breakthrough time with a decline in the flow rates for both DR 80 and MB 9 and the breakthrough behavior was explained using Thomas, Clark, and Yoon-Nelson models., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Improper disposal of huge quantities of fly ash generated by thermal power plants and few other industries contributes to both air and water pollution, and therefore, recent advancements in research are focused toward utilizing this waste material in fabricating useful membranes. This article presents an overview of various methods used to fabricate fly ash-based membranes and critical parameters affecting the same. Fly ash-based membranes also act as the support for fabricating composite membranes and therefore, different means of coating the support membranes are discussed in this paper. Among various methods of membrane fabrication, extrusion method can be considered for bulk production of membranes, which is a pre-requisite for industrial implementation. The article also throws light on a wide range of wastewater that have been successfully treated using these fly ash-based ceramic membranes. However, the use of these membranes should be avoided in acidic solutions as it may cause leaching of heavy metals present in fly ash, causing health hazards. Most of these membranes function on the basis of size exclusion principle, whereas membranes with charge-based separation are also well known. Both of these types of membranes are discussed in this work. Utilization of fly ash-based membranes in separation processes not only reduce the cost associated with the process, but will also intensify the process through various other means such as reduced energy consumption, environmental safety and so on. Thus, the main focus of this review is to present the readers with development and important future directions in this research topic., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships. that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study investigated the potential ofCellulosimicrobium funkeifor degrading dimethyl phthalate (DMP) and diethyl phthalate (DEP). Effect of different initial concentrations of phthalates on their biodegradation and growth ofC. funkeiwas 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 Kiestimated using the Tessier and Edward substrate inhibition models indicated very good tolerance ofC. funkeitoward biodegradation of DMP and DEP., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Membrane photosynthetic microbial fuel cell (MPMFC) utilizes O 2 , NO 3 - and NO 2 - as cathodic electron acceptors, enabling simultaneous treatment of nitrogen, CO 2 and organic carbon in the cathode compartment. In this work, development of a novel cathodic process with in situ nitritation via microalgal photosynthesis during the light period is reported for achieving shortcut nitrogen removal (SNR) from ammonium-rich wastewater. Moreover, a tubular low-cost ceramic membrane was used to separate and recycle the microalgal-bacterial biomass to the cathode compartment during the continuous operation. The influence of NH 4 + concentration and ratio of chemical oxygen demand to total nitrogen on the MPMFC performance was examined. Denitritation under dark and anoxic conditions occurred due to denitrifying bacteria (DNB) subsequent to nitritation under light and aerobic conditions by ammonia-oxidizing bacteria (AOB) in the consortia. Final concentrations of NH 4 + and NO 2 - in the effluent of 0.10 mg NH 4 + -L -1 and 0.02 mg NO 2 - -L -1 , respectively, were obtained using MPMFC which resulted in a nitrogen removal efficiency of 99 ± 0.5%. The maximum electricity production achieved using the MPMFC was 56 ± 0.1 mA. This study demonstrated that combining microalgal photosynthesis, nitritation and denitritation in the cathode compartment of MPMFC is advantageous for avoiding the cost due to external aeration and organic carbon source necessary for ammonium removal as well as utilization of NO 2 - or NO 3 - as an electron acceptor., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Phosphate solubilizing bacteria (PSB) that can withstand high cadmium (Cd) stress is a desired combination for bioremediation. This study evaluated the Cd bioremediation potential of four PSB strains isolated from the contaminated soils of a municipal solid waste (MSW) discarding site (Guwahati, India). PSB strains were cultured in Pikovskaya (PVK) media, which led to higher acid phosphatase (ACP) activity and the release of organic acid. Optical density (OD) measurements were performed to determine the growth pattern of PSB; furthermore, Cd uptake by PSB was evaluated using infrared spectroscopy (IR) and X-Ray Diffraction (XRD) analyses. The 16S rRNA taxonomic analysis revealed that all the four promising PSB strains belonged to either Bacillus sp. or Enterobacter sp. One strain (SM_SS8) demonstrated higher tolerance towards Cd (up to 100 mg L -1 ). Flow cytometry analysis revealed 70.92%, 46.93% and 20.4% viability of SM_SS8 in 10, 50 and 100 mg L -1 , respectively in PVK media containing Cd. This study has therefore substantiated the bioremediation of Cd from polluted soil by the PSB isolates. Thus, experimental results revealed a potential combo benefit, phosphate solubilization along with Cd remediation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

An annular bioreactor (ABR) with wide gap was used for PHB production from Ralstonia eutropha. Hydrodynamic studies demonstrated the uniform distribution of fluid in the ABR due to the Taylor-Couette flow. Thereafter, the ABR was operated at different agitation and sparging rates to study its effect on R. eutropha growth and PHB production. The ABR operated at 500 rpm with air sparge rate of 0.8 vvm yielded a maximum PHB concentration of 14.89 g/L, which was nearly 1.4 times that obtained using a conventional stirred-tank bioreactor (STBR). Furthermore, performances of the bioreactors were compared by operating the reactors under fed-batch mode. At the end of 90 h of operation, the ABR resulted in a very high PHB production of 70.8 g/L. But STBR resulted in a low PHB concentration of 44.2 g/L. The superior performance was due to enhanced oxygen and nutrient mass transfer in the ABR., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The rapid depletion of crude-oil resource which sustains a conventional petroleum refinery together with its environmental impact has led to the search for more sustainable alternatives. In this context, biorefinery serves to fulfil the aim by utilizing waste resources. Hence, this study focused on techno-economic assessment of PHB production at large scale from waste carob pods in a closed-loop biorefinery setup. Firstly, the use of pure sugars in SC1 was shifted to use of carob pods as feedstock in SC2, upgradation of stirred tank bioreactor with novel annular gap bioreactor in SC3 and replacing the conventional centrifugation process with the upcoming ceramic membrane separation process in SC4. An Aspen plus™ flowsheet was developed by including the aforementioned novel strategies for PHB production. The effectiveness of PHB production under various scenarios was evaluated based on its pay-out period and turnover accumulated at the end of 7th year of a PHB plant operation. Instead of pure sugars as the feedstock (SC1), carob pod extract (SC2) reduced the pay-out period from 12.6 to 6.8 years. Likewise, switching onto ABR from the conventional STBR further decreased the pay-out period to 4.8 years. Finally, the use of ceramic membranes (SC4) instead of centrifugation resulted in a similar pay-out period of 4.8 years with increased turnover of about 1.4 billion USD. Thus, the use of carob pods along with an improved PHB titre in ABR and incorporation of affordable ceramic membrane technology for PHB rich biomass separation resulted in a highly cost-effective PHB production strategy., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A native strain of Bacillus paramycoides isolated from the leachate of coal mine overburden rocks was investigated for its potential to produce selenium nanoparticles (SeNPs) by biogenic reduction of selenite, one of the most toxic forms of selenium. 16S rDNA sequencing was used to identify the bacterial strain (SP3). The SeNPs were characterized using spectroscopic (UV-Vis absorbance, dynamic light scattering, X-ray diffraction, and Raman), surface charge measurement (zeta potential), and ultramicroscopic (FESEM, EDX, FETEM) analyses. SP3 exhibited extremely high selenite tolerance (1000 mM) and reduced 10 mM selenite under 72 h to produce spherical monodisperse SeNPs with an average size of 149.1 ± 29 nm. FTIR analyses indicated exopolysaccharides coating the surface of SeNPs, which imparted a charge of -29.9 mV (zeta potential). The XRD and Raman spectra revealed the SeNPs to be amorphous. Furthermore, biochemical assays and microscopic studies suggest that selenite was reduced by membrane reductases. This study reports, for the first time, the reduction of selenite and biosynthesis of SeNPs by B. paramycoides, a recently discovered bacterium. The results suggest that B. paramycoides SP3 could be exploited for eco-friendly removal of selenite from contaminated sites with the concomitant biosynthesis of SeNPs., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Biological sulfide precipitation by sulfate reducing bacteria (SRB) is an emerging technique for the recovery of heavy metals from metal contaminated wastewater. Advantages of this technique include low capital cost, ability to form highly insoluble salts, and capability to remove and recover heavy metals even at very low concentrations. Therefore, sulfate reduction under anaerobic conditions has become a suitable alternative for the treatment of wastewaters that contain metals. However, bioreactor configurations for recovery of metals from sulfate rich metallic wastewater have not been explored widely. Moreover, the recovered metal sulfide nanoparticles could be applied in various fields such as solar cells, dye degradation, electroplating, etc. Hence, metal recovery in the form of nanoparticles from wastewater could serve as an incentive for industries. The simultaneous metal removal and recovery can be achieved in either a single-stage or multistage systems. This paper aims to present an overview of the different bioreactor configurations for the treatment of wastewater containing sulfate and metal along with their advantages and drawbacks for metal recovery. Currently followed biological strategies to mitigate sulfate and metal rich wastewater are evaluated in detail in this review., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The main aim of this work is to test the performance of red mud as a permeable reactive barrier (PRB) material for fluoride removal from water. Batch experiments were carried out to optimise the fluoride removal efficiency (RE) of activated red mud (ARM) based on four selected parameters, namely, the initial fluoride concentration (3-40 mg/L), adsorbent dose (0.5-5 g/L), pH (3.0-11.0) and ionic strength (0.001-0.5 M). Statistical analysis of the results revealed the optimum conditions as initial fluoride concentration -21.46 mg/L, adsorbent dose -2.77 g/L, pH 7.01 and ionic strength -0.24 M, respectively. Under the optimum conditions, fluoride RE of 87.3% was achieved. The individual effects due to initial fluoride concentration, adsorbent dose and ionic strength on fluoride removal were highly significant ( F  = 59.69; P  < 0.005); whereas adsorbent dose, pH and ionic strength showed the greatest squared effects ( F  = 26.05; P  < 0.001). The interaction effect due to initial fluoride concentration and adsorbent dose was also found to be significant ( F  = 12.52; P  = 0.002) for fluoride removal. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses were performed to identify the change in functional group and surface topography following red mud activation.

Polyhydroxybutyrate (PHB) is a natural polyester of microbial origin and is an excellent substitute for petroleum-based food packaging materials. However, moderate mechanical, thermal and barrier properties limit utilization of PHB for commercial food packaging applications. In order to overcome these drawbacks, the present study evaluated the solution casting method for the preparation of PHB nanocomposite by incorporating various concentration (0-1.3 wt%) of graphene nanoplatelets (Gr-NPs). The prepared nanocomposites were tested for their morphology, mechanical, thermal, barrier, cytotoxicity and biodegradable properties. A Gr-NPs concentration of 0.7 wt% was found to be optimum without any agglomeration. In comparison with pristine PHB, the PHB/Gr-NPs nanocomposite showed a higher melting point (by 10 °C), thermal stability (by 10 °C), tensile strength (by 2 times) along with 3 and 2 times reduction in oxygen and water vapour permeability, respectively. The penetration of UV and visible light was greatly reduced with the addition of Gr-NPs. Furthermore, cytotoxic effect of the prepared nanocomposite was found to be statistically insignificant in comparison with the pristine PHB. A four-fold increase in the shelf life was demonstrated by a simulation study conducted using moisture and oxygen-sensitive food items (potato chips and milk product)., Competing Interests: Declaration of competing interest The authors declare that they have no competing interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A novel closed-loop biorefinery model using carob pods as the feed material was developed for PHB production. The carob pods were delignified, and as the second step, sugars present in the delignified carob pods were extracted using water. Ralstonia eutropha and Bacillus megaterium were cultivated on the carob pod extract and its performance was evaluated using Taguchi experimental design. R. eutropha outperformed the B. megaterium in terms of its capability to grow at a maximum initial sugar concentration of 40 g L -1 with a maximum PHB production of 12.2 g L -1 . Finally, the concentrated lignin from the first step was diluted with different proportion of chloroform to extract PHB from the bacterial biomass. The PHB yield and purity obtained were more than 90% respectively using either R. eutropha or B. megaterium. Properties of the PHB produced in this study were examined to establish its application potential., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study evaluated the biological removal of trichloroethylene (TCE) by Rhodococcus opacus using airlift bioreactor under continuous operation mode. The effect of inlet TCE concentration in the range 0.12-2.34 g m -3 on TCE removal has studied for 55 days. During the continuous bioreactor operation, a maximum of 96% TCE removal was obtained for low inlet TCE concentration, whereas the highest elimination capacity was 151.2 g m -3 h -1 for the TCE loading rate of 175.0 g m -3 h -1 . The carbon dioxide (CO 2 ) concentration profile from the airlift bioreactor revealed that the degraded TCE has primarily converted to CO 2 with a fraction of organic carbon utilized for bacterial growth. The artificial neural network (ANN) based model was able to successfully predict the performance of the bioreactor system using the Levenberg-Marquardt (LM) back propagation algorithm, and optimized biological topology is 3:12:1. The prediction accuracy of the model was high as the experimental data were in good agreement (R 2  = 0.9923) with the ANN predicted data. Overall, from the bioreactor experiments and its ANN modeling, the potential strength of R. opacus in TCE biodegradation is proved., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest between authors or any institute or funding agencies., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The inefficiency of cyanide/HCN (CN) binding with heme proteins (under physiological regimes) is demonstrated with an assessment of thermodynamics, kinetics, and inhibition constants. The acute onset of toxicity and CN's mg/Kg LD50 (μM lethal concentration) suggests that the classical hemeFe binding-based inhibition rationale is untenable to account for the toxicity of CN. In vitro mechanistic probing of CN-mediated inhibition of hemeFe reductionist systems was explored as a murburn model for mitochondrial oxidative phosphorylation (mOxPhos). The effect of CN in haloperoxidase catalyzed chlorine moiety transfer to small organics was considered as an analogous probe for phosphate group transfer in mOxPhos. Similarly, inclusion of CN in peroxidase-catalase mediated one-electron oxidation of small organics was used to explore electron transfer outcomes in mOxPhos, leading to water formation. The free energy correlations from a Hammett study and IC50/Hill slopes analyses and comparison with ligands ( CO/ H 2 S/ N 3 - ) $\left( {\text{CO}}/{{{{\text{H}}&#95;{2}}\text{S}}/{\text{N}&#95;{3}^{\text{-}}}\;}\; \right)$ provide insights into the involvement of diffusible radicals and proton-equilibriums, explaining analogous outcomes in mOxPhos chemistry. Further, we demonstrate that superoxide (diffusible reactive oxygen species, DROS) enables in vitro ATP synthesis from ADP+phosphate, and show that this reaction is inhibited by CN. Therefore, practically instantaneous CN ion-radical interactions with DROS in matrix catalytically disrupt mOxPhos, explaining the acute lethal effect of CN.

This study investigated the removal of selenite from wastewater using the fungus Asergillus niger KP isolated from a laboratory scale inverse fluidized bed bioreactor. The effect of different carbon sources and initial selenite concentration on fungal growth, pellet formation and selenite removal was first examined in a batch system. The fungal strain showed a maximum selenite removal efficiency of 86% in the batch system. Analysis of the fungal pellets by field-emission scanning electron microscopy, field-emission transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed the formation of spherical-shaped elemental selenium nanoparticles of size 65-100 nm. An increase in the initial selenite concentration in the media resulted in compact pellets with smooth hyphae structure, whereas the fungal pellets contained hair like hyphae structure when grown in the absence of selenite. Besides, a high initial selenite concentration reduced biomass growth and selenite removal from solution. Using an airlift reactor with fungal pellets, operated under continuous mode, a maximum selenite removal of 94.3% was achieved at 10 mg L -1 of influent selenite concentration and 72 h HRT (hydraulic retention time). Overall, this study demonstrated very good potential of the fungal-pelleted airlift bioreactor system for removal of selenite from wastewater. Graphical abstract.

Since mid-1970s, the proton-centric proposal of 'chemiosmosis' became the acclaimed explanation for aerobic respiration. Recently, significant theoretical and experimental evidence were presented for an oxygen-centric 'murburn' mechanism of mitochondrial ATP-synthesis. Herein, we compare the predictive capabilities of the two models with respect to the available information on mitochondrial reaction chemistry and the membrane proteins' structure-function correlations. Next, fundamental queries are addressed on thermodynamics of mitochondrial oxidative phosphorylation (mOxPhos): (1) Can the energy of oxygen reduction be utilized for proton transport? (2) Is the trans-membrane proton differential harness-able as a potential energy capable of doing useful work? and (3) Whether the movement of miniscule amounts of mitochondrial protons could give rise to a potential of ~200 mV and if such an electrical energy could sponsor ATP-synthesis. Further, we explore critically if rotary ATPsynthase activity of Complex V can account for physiological ATP-turnovers. We also answer the question- "What is the role of protons in the oxygen-centric murburn scheme of aerobic respiration?" Finally, it is demonstrated that the murburn reaction model explains the fast kinetics, non-integral stoichiometry and high yield of mOxPhos. Strategies are charted to further demarcate the two explanations' relevance in the cellular physiology of aerobic respiration., (Copyright © 2019 Elsevier Inc. All rights reserved.)

In this study, bamboo carrier based lab scale compost biofilter was evaluated to treat synthetic waste air containing trichloroethylene (TCE) under continuous operation mode. The effect of inlet TCE concentration and gas flow rate and its removal was investigated. Maximum TCE removal efficiency was found to be 89% under optimum conditions of inlet 0.986 g/m 3 TCE concentration corresponding to a loading rate of 43 g/m 3 h and 0.042 m 3 /h gas flow rate at empty bed residence time (EBRT) of 2 min. For the first time, Artificial Neural Network (ANN) was applied to predict the performance of the compost biofilter in terms of TCE removal. The ANN model used a three layer feed forward based Levenberg-Marquardt algorithm, and its topology consisted of 3-25-1 as the optimum number for the three layers (input, hidden and output). An excellent match between the experimental and ANN predicted the value of TCE removal was obtained with a coefficient of determination (R 2 ) value greater than 0.99 during the model training, validation, testing and overall. Furthermore, statistical analysis of the ANN model performance mediated its prediction accuracy of the bioreactor to treat TCE contaminated systems., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study evaluated a novel shortcut nitrogen removal method using a mixed consortium of microalgae, enriched ammonia oxidizing bacteria (AOB) and methanol utilizing denitrifier (MUD) in a photo-sequencing batch reactor (PSBR) for treating ammonium rich wastewater (ARWW). Alternating light and dark periods were followed to obtain complete biological nitrogen removal (BNR) without any external aeration and with the addition of methanol as the sole carbon source, respectively. The results showed that influent NH 4 + was oxidized to NO 2 - by AOB during the light periods at a rate of 8.09 mg NH 4 + -N L -1 h -1 . Subsequently, NO 2 - was completely reduced during the dark period due to the action of MUD in presence of methanol. The high activities of ammonia monooxygenase (AMO) and nitrite reductase (NIR) enzymes revealed the strong role of AOB and MUD for achieving shortcut nitrogen removal from the wastewater. The reduced activities of nitrate reductase (NR) and nitrite oxidoreductase (NOR) at a high concentration of DO, NH 4 + and NO 2 - in the system further confirmed the nitrogen removal pathway involved in the process. The biomass produced from these experiments showed good settling properties with a maximum sedimentation rate of 0.7-1.8 m h -1 , a maximum sludge volume index (SVI) of 193 ml g -1 - 256 ml g -1 and floc size of 0.2-1.2 mm. In order to describe the growth and interaction among the algae, AOB and MUD for nitrogen removal in the system, the experimental results were fitted to four metabolic models, which revealed best fit of the experimental data due to the models based on algae-AOB and algae-AOB-MUD activities than with the other two models., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, a moving bed biofilm reactor was used for biodesulfuruization using CO as the sole carbon substrate. The effect of hydraulic retention time (HRT), sulfate loading rate and CO loading rate on sulfate and CO removal was examined. At 72, 48 and 24 h HRT, the sulfate removal was 93.5%, 91.9% and 80.1%, respectively. An increase in the sulfate loading reduced the sulfate reduction efficiency, which, however, was improved by increasing the CO flow rate into the MBBR. Best results in terms of sulfate reduction (>80%) were obtained for low inlet sulfate and high CO loading conditions. The CO utilization was very high at 85% throughout the study, except during the last phase of the continuous bioreactor operation it was around 70%. An artificial neural network based model was successfully developed and optimized to accurately predict the bioreactor performance in terms of both sulfate reduction and CO utilization. Overall, this study showed an excellent potential of the moving bed biofilm bioreactor for efficient sulfate reduction even under high loading conditions., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, rhamnolipid (RL) production by Pseudomonas aeruginosa SS14 utilizing rice based Distillers Dried Grains with Solubles (rDDGS) as the sole carbon source was evaluated and the production parameters were optimized using response surface methodology. Highest RL (RL-rDDGS) yield was 14.87 g/L in a culture medium containing 12% (w/v) rDDGS and 11% (v/v) inoculum concentration after 48 h of fermentation at 35 °C. RL-rDDGS was produced as a mixture of mono and di-RL congeners with four novel homologues Rha-C 18:2 , Rha-C 19 , Rha-C 9 , and Rha-Rha-C 19 . The RL reduced the surface tension of water to 34.8 mN/m at a critical micelle concentration (CMC) value of 100 mg/L, exhibited high stability at a wide range of pH (6-12), heating time (0-120 min), and salinity (2-12% NaCl). Furthermore, RL-rDDGS demonstrated appreciable biofilm disruptive property against Candida tropicalis. This is the first report on the usage of rDDGS for sustainable and low cost production of RL., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study reveals the efficient bio-sorption of Cr(VI) species from simulated wastewater using raw (RSV), acid-activated (PSV) and chelated-activated (PSV-C) Sterculia villosa Roxb. shells. Batch optimization experiments were carried out for determining the optimal pH, dosage of bio-sorbent, initial Cr(VI) concentration and incubation temperature. Physico-chemical alterations in the bio-sorbents prior and following bio-sorption of Cr(VI) species were characterized. Equilibrated experimental data at different temperatures was evaluated as a function of time for understanding the isotherm, kinetics and thermodynamics of the bio-sorption process. Sorption rates for all the bio-sorbents (RSV, PSV and PSV-C) alternately fitted to the Langmuir isotherm model and Langmuir maximum adsorption capacity for RSV, PSV and PSV-C were found to be 57.78, 163.51 and 188.68 mg/g, respectively. Cr(VI) sorption by these bio-sorbents followed pseudo-second-order kinetics. Thermodynamic studies suggest endothermic interaction and increased degree of randomness between the bio-sorbents and Cr(VI) species. Regeneration of the bio-sorbents following sorption-desorption revealed that it can be reused and recycled for several times for Cr(VI) removal from wastewater. Graphical abstract.

This study evaluated an enhancement of simultaneous polycyclic aromatic hydrocarbon (PAH) biodegradation and lipid accumulation by Rhodococcus opacus using biochar derived cheaply from biomass gasification effluent. The chemical, physical, morphological, thermal, and magnetic properties of the cheaply derived biochar were initially characterized employing different techniques, which indicated that the material is easy to separate, recover, and reuse for further application. Batch experiments were carried out to study biochar-aided PAH biodegradation by R. opacus clearly demonstrating its positive effect on PAH biodegradation and lipid accumulation by the bacterium utilizing the synthetic media containing 2-, 3- or 4-ring PAH compounds, at an initial concentration in the range 50-200 mg L -1 , along with 10% (w/v) inoculum. An enhancement in PAH biodegradation from 79.6 to 92.3%, 76.1 to 90.5%, 74.1 to 88.2%, and 71.6 to 82.3% for naphthalene, anthracene, phenanthrene, and fluoranthene, respectively, were attained with a corresponding lipid accumulation of 68.1%, 74.2%, 72.4%, and 63% (w/w) of cell dry weight (CDW). From contact angle measurements carried out in the study, enhancement in PAH biodegradation and lipid accumulation due to the biochar was attributed to an improved bioavailability of PAH to the degrading bacterium.

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&#95;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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This work assessed the treatment of wastewater generated from three different industries viz., paper and pulp, biomass gasification and dairy by biodegradation followed by membrane filtration. Batch biodegradation was first carried out using wastewater as the potential substrate for oleaginous Rhodococcus opacus with lipid accumulation intracellular; subsequently, a microfiltration system was applied to recover the bacterial biomass grown as well as for residual chemical oxygen demand (COD) removal from the effluent. The combined process showed excellent results in terms of COD removal from the industrial wastewaters, with the values 56.8%, 46.1% and 68.9% for dairy, paper and pulp and biomass gasification wastewaters, respectively, by biodegradation. These values were further improved to 92.7%, 87.6% and 88.2%, respectively, following the microfiltration step performed by employing a low-cost ceramic membrane. In addition, lipids accumulated by the bacterium were extracted and characterized for biodiesel production potential. Lipid characterization using 1 H NMR confirmed the presence of saturated fatty acids. Gas chromatography analysis of the transesterified lipids revealed the presence of methyl palmitate and methyl stearate. In addition, the estimated properties of the transesterified product affirmed its potential for biofuel application., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Common porous concrete templates (CPCT) and advanced porous concrete templates (APCT) were employed in this study to construct wetlands for their applications in pollutant removal from storm runoff. The planting ability of the concrete was investigated by growing Festuca elata plants in them. Strength of the porous concrete (7.21 ± 0.19 Mpa) decreased by 1.8 and 4.9% over a period of six and 12 months, respectively, due to its immersion in lake water. The height and weight of Festuca elata grass growth on the porous concrete were observed to be 12.6-16.9 mm and 63.4-95.4 mg, respectively, after a duration of one month. Advanced porous concrete template based constructed wetland (APCT-CW) showed better removal of chemical oxygen demand (COD) (49.6%), total suspended solids (TSS) (58.9), NH 3 -N (52.4%), total nitrogen (TN) (47.7%) and total phosphorus (TP) (45.5%) in storm water, when compared with the common porous concrete template based constructed wetland (CPCT-CW) with 20.6, 29.8, 30.1, 35.4 and 26.9%, respectively. The removal of Pb, Ni, Zn by the CPCT-CW unit were 28.9, 33.3 and 42.3%, respectively, whereas these were 51.1, 62.5 and 53.8%, respectively, with the APCT-CW unit. These results demonstrate that the advanced porous concrete template in constructed wetland could be employed successfully for the removal of pollutants from urban storm water runoff.

This study examined immobilized anaerobic biomass for sulfate reduction using carbon monoxide (CO) as the sole carbon source under batch and continuous fed conditions. The immobilized bacteria with beads made of 10% polyvinyl alcohol (PVA) showed best results in terms of sulfate reduction (84 ± 3.52%) and CO utilization (98 ± 1.67%). The effect of hydraulic retention time (HRT), sulfate loading rate and CO loading rate on sulfate and CO removal was investigated employing a 1L packed bed bioreactor containing the immobilized biomass. At 48, 24 and 12 h HRT, the sulfate removal was 94.42 ± 0.15%, 89.75 ± 0.47% and 61.08 ± 0.34%, respectively, along with a CO utilization of more than 90%. The analysis of variance (ANOVA) of the results obtained showed that only the initial CO concentration significantly affected the sulfate reduction process. The reactor effluent sulfate concentrations were 27.41 ± 0.44, 59.16 ± 1.08, 315.83 ± 7.33 mg/L for 250, 500 and 1000 mg/L of influent sulfate concentrations respectively, under the optimum operating conditions. The sulfate reduction rates matched well with low inlet sulfate loading rates, indicating stable performance of the bioreactor system. Overall, this study yielded very high sulfate reduction efficiency by the immobilized anaerobic biomass under high CO loading condition using the packed bed reactor system., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Heavy metal removal was evaluated using sodium alginate immobilized sulfate reducing bacteria (SRB) under batch and continuous mode. Under batch conditions, more than 95% metal removal was achieved due to formation of insoluble metal sulfides exterior to the bead surface. Best heavy metal removal results were obtained at 48 h hydraulic retention time (HRT). Metal loading rate values upto 2.20 mg/L∙h for Fe(III), Zn(II), Cd(II), Pb(II) and Ni(II) and upto 4.29 mg/L∙h for Cu(II) were proved to be favorable for their removal using the continuous downflow column reactor packed with the immobilized SRB beads. Continuous metal removal from a mixture of the heavy metals showed that Cu(II) removal was maximum (99%), followed by Zn(II) (95.8%) and other metals at their respective low inlet concentrations. However, the removal values were reduced at a high inlet concentration of these metals, which matched well with low COD and sulfate reduction values., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In the current industrial scenario, chromium (Cr) as a metal is of great importance, but poses a major threat to the environment. Phytoremediation provides an environmentally sustainable, ecofriendly, cost effective approach for environmental cleanup of Cr. This review presents the current status of phytoremediation research with particular emphasis on cleanup of Cr contaminated soil and water systems. It gives a detailed account of the work done by different authors on the Cr bioavailability, uptake pathway, toxicity and storage in plants following the phytoextraction mechanism. This paper also describes recent findings related to Cr localization in hyperaccumulator plants. It gives an insight into the processes and mechanisms that allow plants to remove Cr from contaminated sites under varying conditions. These detailed knowledge of changes in plant metabolic pool in response to Cr stress would immensely help understand and improve the phytoextraction process. Further, this review provides a detailed understanding of Cr uptake and detoxification mechanism by plants that can be applied in developing a suitable approach for a better applicability of the process., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Discharge of wastewater from electroplating and leather industries is a major concern for the environment due to the presence of toxic Cr 6+ and other ions, such as sulfate, nitrate, phosphate, etc. This study evaluated the potential of Tradescantia pallida, a plant species known for its Cr bioaccumulation, for the simultaneous removal of Cr 6+ , SO 4 2- , NO 3 - , and PO 4 3- . The effect of different co-ions on Cr 6+ removal by T. pallida was examined following the Plackett-Burman design of experiments carried out under batch hydroponics conditions. The results revealed a maximum removal of 84% Cr 6+ , 87% SO 4 2- , 94% NO 3 - and 100% PO 4 3- without any phytotoxic effect on the plant for an initial Cr 6+ concentration in the range 5-20 mg L -1 . SO 4 2- and NO 3 - enhanced Cr uptake at a high initial Cr concentration (20 mg L -1 ), whereas PO 4 3- did not affect Cr uptake both at high and low initial Cr concentrations. The Cr 6+ removal kinetics in the presence of different ions was well described by the pseudo-second-order kinetic model which revealed that both biosorption and bioaccumulation of the metal played an important role in Cr 6+ removal. Increase in the total carbohydrate and protein content of the plant following Cr 6+ and co-ions exposure indicated a good tolerance of the plant toward Cr 6+ toxicity. Furthermore, enhancement in the lipid peroxidation and catalase activity in T. pallida upon Cr 6+ exposure revealed a maximum stress-induced condition in the plant. Overall, this study demonstrated a very good potential of the plant T. pallida for Cr 6+ removal from wastewater even in the presence of co-ions.

Microbial biosorption has evolved as an effective strategy for heavy metal removal from contaminated waters. The common cyanobacterium Nostoc muscorum isolated from the banks of a polluted river in Meghalaya, India, was tested for its potential to remove Zn 2+ from aqueous solutions. Energy-dispersive X-ray (EDX) study verified Zn binding on the cyanobacterial biomass, and FTIR analysis revealed many negatively charged functional groups (hydroxyl, carbonyl, alcohol, amine, phosphoryl, sulfhydryl, and carboxyl) on the cell surface that aided in metal binding. Thermodynamic studies established the biosorption process to be energetically favorable with negative free energy change (-10.404, -10.599, and -10.796 kJ/mol at 298, 303, and 308 K, respectively). Sorption isotherm data fitted best in the Langmuir isotherm indicating monolayer nature of Zn sorption. The organism showed hyper-accumulation tendency towards Zn with a maximum sorption capacity as high as 2500 mg of Zn taken up per gram of biomass. The separation factor R L calculated from Langmuir isotherm ranged between 0 and 1 signifying favorable interaction between the cyanobacterial biomass and the Zn ions. Various experimental parameters, viz. pH, temperature, inoculum age and size, and shaking rate, influenced Zn biosorption. Optimized experimental conditions significantly enhanced the sorption percentage. Sorption was primarily a fast surface phenomenon in the beginning with internalization of zinc ions by the live cells on prolonged exposure.

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 -1 . The heavy metals tested were Fe(III), Cu(II), Zn(II), Cd(II), Ni(II), and Pb(II) at 10 mg L -1 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 2 -(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.

This study evaluated the combined effect of Cd(II), Cu(II), Ni(II), Fe(III), Pb(II) and Zn(II) on each other removal by anaerobic biomass under sulfate reducing condition. Statistically valid Plackett-Burman design of experiments was employed to carry out this mixture study. The results obtained showed a maximum removal of Cu(II) (98.9%), followed by Ni(II) (97%), Cd(II) (94.8%), Zn(II) (94.6%), Pb(II) (94.4%) and Fe(III) (93.9%). Analysis of variance (ANOVA) of the sulfate and chemical oxygen demand (COD) reduction revealed that the effect due to copper was highly significant (P value<0.05) on sulfate and COD removal. To establish the role of sulfate reducing bacteria (SRB) in the metal removal process, surface morphology and composition of the metal loaded biomass were analyzed by transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS) and by field emission scanning electron microscopy (FESEM) integrated with energy dispersive X-ray spectroscopy (EDX). The results obtained revealed that the metal precipitates are associated with the outer and inner cell surface of the SRB as a result of the sulfide generated by SRB., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The effect of dissolved oxygen (DO) level and pH (controlled/uncontrolled) was first studied to enhance the production of novel glutaminase-free L-asparaginase by Pectobacterium carotovorum MTCC 1428 in a batch bioreactor. The optimum level of DO was found to be 20%. The production of L-asparaginase was found to be maximum when pH of the medium was maintained at 8.5 after 12 h of fermentation. Under these conditions, P. carotovorum produced 17.97 U/mL of L-asparaginase corresponding to the productivity of 1497.50 U/L/h. The production of L-asparaginase was studied in fed-batch bioreactor by feeding L-asparagine (essential substrate for production) and/or glucose (carbon source for growth) at the end of the reaction period of 12 h. The initial medium containing both L-asparagine and glucose in the batch mode and L-asparagine in the feeding stream was found to be the best combination for enhanced production of glutaminase-free L-asparaginase. Under this condition, the L-asparaginase production was increased to 38.8 U/mL, which corresponded to a productivity of 1615.8 U/L/h. The production and productivity were increased by 115.8% and 7.9%, respectively, both of which are higher than those obtained in the batch bioreactor experiments.

In this study, effect of different parameters, viz. concentration of photosensitizer (PS), pH of the bacterial cell suspension and initial cell count, on photo-inactivation of Escherichia coli and Enterococcus hirae bacteria using methylene blue (MB) and sodium anthraquinone-2-sulphonate (SAQS) was investigated employing the statistically valid full factorial design of experiments. The inactivation efficiency of E. hirae using MB ranges between 10.81 and 48.55 %, whereas in the case of E. coli it ranges between 10.41 and 46.44 %. Using SAQS, the inactivation efficiency of E. hirae was within 5.26-39.03 %, and in the case of E. coli it varied in the range 4.65-37.66 %. Statistical analysis of the photo-inactivation results in the form of analysis of variance (ANOVA) and student 't' test revealed significant individual effect of these process parameters. In addition, an increase in dark incubation period with MB or SAQS resulted in enhanced photo-inactivation efficiency against both the microorganisms. Reactive oxygen species measurement and analysis of lipid peroxidation and protein carbonyl index helped in a better understanding of the photo-inactivation mechanism.

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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)