Development and characterization of active poly (3-hydroxybutyrate) based composites with grapeseed oil and MgO nanoparticles for shelf-life extension of white button mushrooms (Agaricus bisporus).

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.

Neuro-fuzzy modelling of a continuous stirred tank bioreactor with ceramic membrane technology for treating petroleum refinery effluent: a case study from Assam, India.

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 (CODRE) (%) 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 (R2), 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 CODRE (93%) and lipid concentration (2.8 g/L) could be obtained consistently.

Facile fabrication and characterization of novel antimicrobial and antioxidant poly (3-hydroxybutyrate)/essential oil composites for potential use in active food packaging applications.

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/dm2).

Biodegradation of low, medium and high molecular weight phthalate by Gordonia sp. in a batch system: Kinetics and phytotoxicity analyses.

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 R2 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.

100% degradation of DBP and DMP was achieved at 200­1000 mg/L initial concentrations.This is the first study on evaluation of DMP, DBP, and DnOP inhibition on Gordonia sp.Teisser model accurately described the inhibitory effect of phthalate.DMP and DEP degraded samples (1000 mg/L Initial concentration) showed negligible effect on chickpea seeds germination.

An indigenous tubular ceramic membrane integrated bioreactor system for biodegradation of phthalates mixture from contaminated wastewater.

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.

Lutein Production by Halophilic Microalgae Using Anaerobic Digestate as the Substrate and Its Potential Application as a Biopesticide.

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, MgCl2, NaCl, NaHCO3 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.

Both biogenic and chemically synthesized metal sulfide nanoparticles induce oxidative stress and enhance lipid accumulation in Rhodococcus opacus.

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.

Chitosan production by Penicillium citrinum using paper mill wastewater and rice straw hydrolysate as low-cost substrates in a continuous stirred tank reactor.

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.

Predictive modelling and optimization of an airlift bioreactor for selenite removal from wastewater using artificial neural networks and particle swarm optimization.

Selenite (Se4+) 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 (REselenite) (%) was predicted through two input parameters, namely, the influent selenite concentration (ICselenite) (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 REselenite was maximized while minimizing the HRT for a preferably higher range of ICselenite. Thus, the most favourable optimum conditions were suggested as: ICselenite - 50.45 mg/L and HRT - 24 h, resulting in REselenite of 69.4%. Overall, it can be inferred that ANN models can successfully substitute knowledge-based models to predict the REselenite in an ALR, and the process parameters can be effectively optimized using PSO.

Recent advances and future prospects of cellulose, starch, chitosan, polylactic acid and polyhydroxyalkanoates for sustainable food packaging applications.

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.

Novel biologically synthesized metal nanopowder from wastewater for dye removal application.

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 m2/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.

Process intensification through waste fly ash conversion and application as ceramic membranes: A review.

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.

Bioelectricity production and shortcut nitrogen removal by microalgal-bacterial consortia using membrane photosynthetic microbial fuel cell.

Membrane photosynthetic microbial fuel cell (MPMFC) utilizes O2, NO3- and NO2- as cathodic electron acceptors, enabling simultaneous treatment of nitrogen, CO2 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 NH4+ 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 NH4+ and NO2- in the effluent of 0.10 mg NH4+-L-1 and 0.02 mg NO2--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 NO2- or NO3- as an electron acceptor.

Bacterial strains found in the soils of a municipal solid waste dumping site facilitated phosphate solubilization along with cadmium remediation.

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.

Mass balance and kinetics of biodegradation of endocrine disrupting phthalates by Cellulosimicrobium funkei in a continuous stirred tank reactor system.

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.

Selenite bioreduction and biosynthesis of selenium nanoparticles by Bacillus paramycoides SP3 isolated from coal mine overburden leachate.

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.

A novel rotating wide gap annular bioreactor (Taylor-Couette type flow) for polyhydroxybutyrate production by Ralstonia eutropha using carob pod extract.

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.

Techno-economic assessment of a sustainable and cost-effective bioprocess for large scale production of polyhydroxybutyrate.

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.

Recent advances in heavy metal recovery from wastewater by biogenic sulfide precipitation.

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.

A closed-loop biorefinery approach for polyhydroxybutyrate (PHB) production using sugars from carob pods as the sole raw material and downstream processing using the co-product lignin.

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.