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).

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.

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.

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.

Experimental study on fabrication, biocompatibility and mechanical characterization of polyhydroxybutyrate-ball clay bionanocomposites for bone tissue engineering.

The poly (3-hydroxybutyrate) (PHB)/ball clay nanocomposites (B1-B10) were synthesized using solvent casting method with different weight percentage of ball clay in PHB matrix. Scanning electron microscope (SEM) showed maximum root mean square roughness (188.73 µm) for 10% ball clay loading. Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) showed establishment of intercalated structure and formation of hydrogen bond between ball clay and PHB matrix. Contact angle values (67.3 - 51.3°) exhibited that the nanocomposites (B1-B10) are more hydrophilic than neat PHB (70.30°). Thermogravimetric (TGA) and differential scanning calorimetry (DSC) revealed maximum Tmax (278 °C) and Tm (175 °C) for the nanocomposite B10 (PHB/PEG/ball clay: 80%/10%/10%). Maximum tensile strength (38.21 ± 0.15 MPa) and Young's modulus (1.74 ± 0.016 GPa) was observed for B10 nanocomposite. The values of protein adsorption, platelet adhesion, PT, APTT and complement activation for B10 nanocomposites were 165 ± 2 µg/cm2, 72 ± 3 × 109 platelets/cm2, 23 ± 1 s, 44 ± 2 s, 102 ± 2 mg/dL and 631 ± 3 mg/dL, respectively. Hydroxyapatite formation was also observed for nanocomposite (B10) in in vitro simulated body fluid (SBF) study. Finally, the nanocomposite (B10) showed no harmful effect on MG-63 cells, indicating that they are physiologically safe.

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.

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.

Separation of bacteria Kocuria rhizophila BR-1 from its broth during synthesis of gold nanoparticles using ceramic membrane by shear-enhanced filtration process.

In the present study, disc type ceramic membranes made from China clay, quartz and calcium carbonate were used for the separation of bacteria Kocuria rhizophila from its broth by shear-enhanced filtration process. Porosity, water permeability and average pore size of the membrane were 42%, 3.24 × 10-4 L m-2 h-1 Pa-1 and 180 nm, respectively. The membrane exhibited good chemical tolerance in acid, alkali and chlorine solutions. The effect of trans-membrane pressure and rotational speed on permeate flux and bacterial rejection was investigated. It was found that the permeate flux increased (40-163.5 L m-2 h-1) and bacterial rejection decreased (99.2-94.5%) with increasing pressure (69-345 kPa). With an increase in rotation (50-250 rpm), the permeate flux increased from 156.5 to 176.8 L m-2 h-1, while bacterial rejection decreased from 94.3 to 83.2%. The pressure of 345 kPa and rotational speed of 250 rpm with flux of 176.8 L m-2 h-1 and rejection of 83% was selected as an optimum process condition. The analysis of fouling models revealed that the cake filtration model provided the highest R2 (0.89) value followed by intermediate pore blocking (0.87) which indicates that cake filtration model has the best fit with the experimental data. Henceforth, the shear enhanced filtration process used in this study can be considered as a pertinent filtration process for efficient recovery of biological products at industrial scale.

Credibility of polymeric and ceramic membrane filtration in the removal of bacteria and virus from water: A review.

The prevalence of many waterborne diseases and the increased mortality rate starting from children to adult persons rises the need to purify water before consumption. Owing to the number of advantages associated with membrane filtration technologies, they are widely being implemented across the world for the production of pathogen free water. This article hence focuses on numerous such examples of using membrane technology in the production of drinking water. Membranes are even being coated with various materials to enhance their surface properties such as electrostatic and hydrophobic attraction capacity to aid for such separation. Various metal oxide coatings are seen to be gaining importance now-a-days and also, articles citing the use of silver coating are very large in number, owing to the excellent antipathogenic property shown by various silver compounds. It needs mention that examples have also been cited in this article where virus concentration was carried out with a purpose of producing different vaccines, virus adsorption in membrane and its subsequent elution (VIRADEL) being the most discussed one. In addition to these, description about the virus and bacteria quantification techniques are also mentioned in this article. The elaborated study of all these processes and the derived future prospects regarding the production of pathogen free water will certainly be helpful for the researchers working in this field, irrespective of the beginners or the experienced ones, to direct their research more innovatively.

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.

Preparation and characterization of environmentally safe and highly biodegradable microbial polyhydroxybutyrate (PHB) based graphene nanocomposites for potential food packaging applications.

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).

Novel shortcut biological nitrogen removal method using an algae-bacterial consortium in a photo-sequencing batch reactor: Process optimization and kinetic modelling.

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 NH4+ was oxidized to NO2- by AOB during the light periods at a rate of 8.09 mg NH4+-N L-1h-1. Subsequently, NO2- 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, NH4+ and NO2-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-1and 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.

A novel integrated biodegradation-microfiltration system for sustainable wastewater treatment and energy recovery.

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 1H 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.

Investigating the properties of poly (lactic acid)/exfoliated graphene based nanocomposites fabricated by versatile coating approach.

In order to overcome the challenges that underlies in dispersion of exfoliated graphene (GR) into poly lactic acid (PLA) matrix by extrusion, a versatile approach is used in this work, where uniform coating of GR over PLA is carried out prior to extrusion of PLA. Effect of melt processing on different graphene loaded composites (PLA-M-0.05GR, PLA-M-0.2GR) is studied. Investigation on the morphology, thermal stability, crystallization property, surface wettability, mechanical property, and dynamic mechanical property of composites are performed. XRD analysis and morphological analysis confirm the formation of well dispersed composite. Thermo-gravimetric analysis and kinetic study reveal significant improvement in thermal stability. Improvement in crystallinity, melting point, crystallization point are found from DSC analysis. Crystallization kinetic study is carried out and nucleation effect of the GR on crystallization of PLA chain is noticed. Hydrophobicity of the PLA composites is increased by the incorporation of graphene. Tensile strength of the composites is noticed to be increased as compared to PLA-M. An improvement of storage modulus for the composites over PLA-M is observed by Dynamic mechanical analysis.

Simultaneous heavy metal removal and anthracene biodegradation by the oleaginous bacteria Rhodococcus opacus.

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, -CH2-(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.