Effect of leachate recycle and inoculation on microbial characteristics of municipal refuse in landfill bioreactors

Population development of key groups of anaerobic and aerobic bacteria involved in municipal refuse decomposition under laboratory landfill bioreactors with and without leachate recycle and inoculation was measured since modeling municipal refuse was landfilled in bioreactors for about 210 days. Hydrolytic fermentative bacteria (HFB), hydrogen-producing acetogenic bacteria (HPAB), methane-producing bacteria (MPB), sulfate-reducing bacteria (SRB), anaerobic and aerobic cellulolytic bacteria and denitrabacteria were enumerated by the most probable number technique. The results showed that the dominant microorganism groups were the methanogenic bacteria including hydrolytic fermentative, hydrogen-producing acetogenic and methane-producing bacteria. They were present in fresh refuse but at low values and positively affected by leachate recycle and refuse inoculation. The amounts of HFB or HPAB in digesters D4 and D5 operated with inoculation and leachate recycle reached their maximum values of 1010 - 1012 cells/g dry refuse for HFB or 105 - 106 cells/g dry refuse for HPAB on day 60, in digester D3 operated with leachate recycle on day 120 for HFB (109 cells/g dry refuse) or on day 90 for HPAB (105 cells/g dry refuse), and in digesters D1 and D2 on day 210 for HFB (109 cells/g dry refuse) or on day 90 for HPAB (104 - 106 cells/g dry refuse). The population of methane-producing bacteria in digesters D4 and D5 sharply increased on days 60 and 90 respectively, however in digesters D1, D2 and D3 on day 120. Leachate recycle and inoculation changed the cellulolytic microorganisms composition of refuse ecosystem, the higher amounts of anaerobic cellulolytic bacteria were measured in digesters D4 and D5 (107 cells/g dry refuse), followed by digesters D3 (106 cells/g dry refuse), D2 or D1 (104 cells/g dry refuse). However, the amounts of aerobic cellulolytic bacteria were much lower than that of anaerobic cellulolytic bacteria. And it was higher in digesters D3 than those in digesters D1, D2, D4 and D5. The amounts of SRB and denitrabacteria were also higher in digester D5 than those in digesters D1, D2, D3 and D4. Refuse decomposition could be accelerated by leachate recycle and inoculation in the view of microorganism development.

Embryoid body formation from embryonic and induced pluripotent stem cells:Benefits of bioreactors

Embryonic stem(ES)cells have the ability to differ-entiate into all germ layers,holding great promise not only for a model of early embryonic development but also for a robust cell source for cell-replacement therapies and for drug screening.Embryoid body (EB)formation from ES cells is a common method for producing different cell lineages for further applications. However,conventional techniques such as hanging drop or static suspension culture are either inherently incapable of large scale production or exhibit limited control over cell aggregation during EB formation and subsequent EB aggregation.For standardized mass EB production,a well defined scale-up platform is necessary.Recently,novel scenario methods of EB formation in hydrodynamic conditions created by bioreactor culture systems using stirred suspension systems(spinner flasks),rotating cell culture system and rotary orbital culture have allowed large-scale EB formation.Their use allows for continuous monitoring and control of the physical and chemical environment which is difficult to achieve by traditional methods.This review summarizes the current state of production of EBs derived from pluripotent cells in various culture systems.Furthermore,an overview of high quality EB formation strategies coupled with systems for in vitro differentiation into various cell types to be applied in cell replacement therapy is provided in this review. Recently,new insights in induced pluripotent stem(iPS) cell technology showed that differentiation and lineage commitment are not irreversible processes and this has opened new avenues in stem cell research.These cells are equivalent to ES cells in terms of both self-renewal and differentiation capacity.Hence,culture systems for expansion and differentiation of iPS cells can also apply methodologies developed with ES cells,although direct evidence of their use for iPS cells is still limited.

Understanding the scale-up of fermentation processes from the viewpoint of the flow field in bioreactors and the physiological response of strains

The production capability of a fermentation process is predominately determined by individual strains,which ultimately affected ultimately by interactions between the scale-dependent flow field developed within bioreactors and the physiological response of these strains.Interpreting these complicated interactions is key for better understanding the scale-up of the fermentation process.We review these two aspects and address progress in strategies for scaling up fermentation processes.A perspective on how to incorporate the multiomics big data into the scale-up strategy is presented to improve the design and operation of industrial fermentation processes.

An Approach for Micropropagation of Blueberry (<i>Vaccinium corymbosum</i>L.) Plants Mediated by Temporary Immersion Bioreactors (TIBs)

A new procedure for blueberry (Vaccinium corymbosum L.) micropropagation in programmed Temporary Immersion Bioreactors (TIBs based on two separate bottles) was developed for the commercial genotypes Biloxi, Sharp Blue and Brillita. Plant cultures were developed in a controlled environment with 0.4 MPa CO2 enrichment, sucrose-reduced medium, and light intensity of 60 mM m-2·s-1. Principal component analysis showed that component 1 (C1) grouped 64.08% of the total variability, while the first two components accounted for 86.97%. Representation of the principal components demonstrated three clusters corresponding with the blueberry genotypes, and within each cluster plants micropropagated in agar-base medium grouped separately from those plants multiplied in TIBs. Both plant number and total internodes traits (related to the productive efficiency) were demonstrated superior in blueberries propagated in TIBs. Additionally, when transferred to greenhouse conditions, blueberries propagated in TIBs showed higher adaptability and growing rates than those cultured by the conventional approach, altogether evidencing the occurrence of a photomixotrophic stage in the vitroplantlets cultured in TIBs.

A computational analysis of the impact of mass transport and shear on three-dimensional stem cell cultures in perfused micro-bioreactors

In this study, Computational Fluid Dynamics(CFD) is used to investigate and compare the impact of bioreactor parameters(such as its geometry, medium flow-rate, scaffold configuration) on the local transport phenomena and, hence, their impact on human mesenchymal stem cell(hM SC) expansion. The geometric characteristics of the TissueFlex174;(Zyoxel Limited, Oxford, UK) microbioreactor were considered to set up a virtual bioreactor containing alginate(in both slab and bead configuration) scaffolds. The bioreactor and scaffolds were seeded with cells that were modelled as glucose consuming entities. The widely used glucose medium, Dulbecco's Modified Eagle Medium(DMEM), supplied at two inlet flow rates of 25 and 100 μl·h^(-1), was modelled as the fluid phase inside the bioreactors. The investigation, based on applying dimensional analysis to this problem, as well as on detailed three-dimensional transient CFD results, revealed that the default bioreactor design and boundary conditions led to internal and external glucose transport, as well as shear stresses, that are conducive to h MSC growth and expansion. Furthermore, results indicated that the ‘top-inout' design(as opposed to its symmetric counterpart) led to higher shear stress for the same media inlet rate(25 μl·h^(-1)), a feature that can be easily exploited to induce shear-dependent differentiation. These findings further confirm the suitability of CFD as a robust design tool.

Simple Protocol for the Micropropagation of Teak(Tectona grandis Linn.)in Semi-Solid and Liquid Media in RITA^(█) Bioreactors and ex Vitro Rooting

In Latin America the forestry of exotic species such as teak has been increasing in recent decades, due to their advantages in wood quality, rapid growth;and the relative ease of producing clones and their multiplication with respect to native species. Therefore, there is great interest in developing larger-scale propagation strategies that reduce costs and intensive manual labor. Culture in liquid media with temporary immersion and the semi-automation of the system has raised expectations for large-scale micropropagation. We report a protocol for teak, which reuses the primary explants in several culture cycles in semi-solid medium to produce nodal explants for the multiplication phase in temporary immersion bioreactors (RITA&reg;). The control of factors such as cytokinin concentration, explants density, immersion frequencies and culture duration was analyzed. The number of shoots increased with 0.5 mg&middot;l-1 of BA (6-Benzyladenine), alone or in combination with 0.5 mg&middot;l-1 of Kinetin, with 2 daily immersions of 1 minute each;however, these shoots showed a high degree of hyperhydricity. When 0.05 mg&middot;l-1 of BA was used with 1 immersion of 1 minute every 2 days, the hyperhydricity decreased. Although the number of shoots was lower, they showed good length to be used during multiplication and rooting ex vitro. Our results suggest that teak micropropagation can be simplified in two phases in vitro, the establishment and multiplication;followed by rooting ex vitro and acclimatization. This would imply a reduction in production costs, since most of the multiplication would take place in RITA&reg;containers.

Engineering stem cell niches in bioreactors

Stem cells, including embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells and amniotic fluid stem cells have the potential to be expanded and differentiated into various cell types in the body.Efficient differentiation of stem cells with the desired tissue-specific function is critical for stem cell-based cell therapy, tissue engineering, drug discovery and disease modeling. Bioreactors provide a great platform to regulate the stem cell microenvironment, known as "niches",to impact stem cell fate decision. The niche factors include the regulatory factors such as oxygen, extracellular matrix(synthetic and decellularized), paracrine/autocrine signaling and physical forces(i.e., mechanical force, electrical force and flow shear). The use of novel bioreactors with precise control and recapitulation of niche factors through modulating reactor operation parameters can enable efficient stem cell expansion and differentiation. Recently, the development of microfluidic devices and microbioreactors also provides powerful tools to manipulate the stem cell microenvironment by adjusting flow rate and cytokine gradients. In general,bioreactor engineering can be used to better modulate stem cell niches critical for stem cell expansion, differentiation and applications as novel cell-based biomedicines. This paper reviews important factors that can be more precisely controlled in bioreactors and their effects on stem cell engineering.

Progress in bioreactors of bioartificial livers

BACKGROUND: Bioartificial liver support systems are becoming an effective therapy for hepatic failure. Bioreactors, as key devices in these systems, can provide a favorable growth and metabolic environment, mass exchange, and immunological isolation as a platform. Currently, stagnancy in bioreactor research is the main factor restricting the development of bioartificial liver support systems. DATA SOURCES: A PubMed database search of English-language literature was performed to identify relevant articles using the keywords 'bioreactor', 'bioartificial liver', 'hepatocyte', and 'liver failure'. More than 40 articles related to the bioreactors of bioartificial livers were reviewed. RESULTS: Some progress has been made in the improvement of structures, functions, and modified macromolecular materials related to bioreactors in recent years. The current data on the improvement of bioreactor configurations for bioartificial livers or on the potential of the use of certain scaffold materials in bioreactors, combined with the clinical efficacy and safety evaluation of cultured hepatocytes in vitro, indicate that the AMC (Academic Medical Center) BAL bioreactor and MELS (modular extracorporeal liver support) BAL bioreactor system can partly replace the synthetic and metabolic functions of the liver in phase I clinical studies. In addition, it has been indicated that the microfluidic PDMS (polydimethylsiloxane) bioreactor, or SlideBioreactor, and the microfabricated grooved bioreactor are appropriate for hepatocyte culture, which is also promising for bioartificial livers. Similarly, modified scaffolds can promote the adhesion, growth, and function of hepatocytes, and provide reliable materials for bioreactors. CONCLUSIONS: Bioreactors, as key devices in bioartificial livers, play an important role in the therapy for liver failure both now and in the future. Bioreactor configurations are indispensable for the development of bioartificial livers used for liver failure, just as the modified scaffold materials available for bioreactors are favorable to the construction of effective bioartificial livers.

Effect of leachate recycling and inoculation on the biochemical characteristics of municipal refuse in landfill bioreactors

Activity development of key groups of enzymes involved in municipal refuse decomposition was measured in laboratory landfill bioreactors with and without leachate recycling and inoculation for about 210 days. The results showed that the enzymes (amylase, protease, cellulase, lipase and pectinase) were present in fresh refuse but at low values and positively affected by leachate recycling and refuse inoculation. The total average of cellulase activity in digesters D3 operated with leachate recycling but no inoculation, D4 and D5 operated with leachate recycling and inoculation was much higher than that in digesters D1 and D2 without leachate recycling and inoculation by 88%—127%, 117%—162% and 64%—98%. The total average of protease activity was higher in digester D4 than that in digesters D1, D2, D3 and D5 by 63%, 39%, 24% and 24%, respectively, and the positive effect of leachate recycling and inoculation on protease activity of landfilled refuse mainly was at the first two months. The total average of amylase activity was higher in digesters D3, D4 and D5 than that in digesters D1 and D2 by 83%—132%, 96%—148% and 81%—129%. During the early phase of incubation, the stimulatory effect of inoculation on lipase activity was measured, but refuse moisture was the main factor affecting lipase activity of landfilled refuse. The inoculation, initial and continuous inoculation of microorganisms existing in leachate, was the mainly stimulatory factor affecting pectinase activity of landfilled refuse.

Anaerobic Membrane Bioreactors (AnMBR) for Wastewater Treatment

This paper focuses on the recent research in the development of anaerobic membrane bioreactors in wastewater treatment. Anaerobic wastewater treatment technology is gaining increasing attention due to its capacity to convert wastewater BODs to usable biogas with relatively low energy consumption. The anaerobic membrane bioreactor (AnMBR), which is a combination of the anaerobic biological wastewater treatment process and membrane filtration, represents a recent development in the high-rate anaerobic bioreactors. This paper reviews applications and performances of AnMBR and the membrane filtration behaviour in AnMBRs.

Comparative Analysis of Hydrodynamics Behavior of Microalgae Suspension Flow in Circular, Square and Hexagonal Shape Photo Bioreactors

Microalgae based biofuel is an emerging natural source of energy alternative to the fossil fuel. As microalgae are photosynthetic microorganisms, light is one of the limiting factors for its culture. Though many researches have been carried out for findings behind suitable culture system for the proper growth of microalgae, those are confined only to tubular Photo-bioreactor (PBR). This paper aims to make comparison among the horizontal loop photo bioreactors with different cross sections based on the analysis of hydrodynamics behavior. Three different geometrical shapes having vertical cross sections of circular, square and hexagonal PBR, have been proposed taking into account light intensity for microalgae culture. In this study, we simulate the flow dynamics of three types of PBRs and discuss the velocity, pressure and shear stress properties as microalgae endurance capacity depends on them. For the dimension of the three PBRs we considered here, each of them have radius of about 0.05 m while the length together with bending portion is approximately 20.5 m for a single loop. From the study, the hydrodynamic behaviors are observed to be quite dissimilar in case of three PBR’s. In the straight portion the velocity profile is quite parabolic in tubular but distorted minimally in case of square and hexagonal PBRs. In the middle of the U-loop, a haphazard fluid distribution is noticed. The velocity magnitude and agitation of microalgae cells are higher in hexagonal than in square and tubular. The shear rate is less in case of tubular compared to square and hexagonal. A linear pressure drop is found from the inlet to the outlet for three PBR’s. From this comparison, it can be said that the tubular one would be the best option for microalgae culture in case of industrial purposes.

Hydrodynamics research of wastewater treatment bioreactors

To optimize the design and improve the performance of wastewater treatment bioreactors,the review concerning the hydrodynamics explored by theoretical equations,process experiments,modeling of the hydrodynamics and flow field measurement is presented. Results of different kinds of experiments show that the hydrodynamic characteristics can affect sludge characteristics,mass transfer and reactor performance significantly. Along with the development of theoretical equations,turbulence models including large eddy simulation models and Reynolds-averaged Navier-Stokes (RANS) models are widely used at present. Standard and modified k-ε models are the most widely used eddy viscosity turbulence models for simulating flows in bioreactors. Numerical simulation of hydrodynamics is proved to be efficient for optimizing design and operation. The development of measurement techniques with high accuracy and low intrusion enables the flow filed in the bioreactors to be transparent. Integration of both numerical simulation and experimental measurement can describe the hydrodynamics very well.

Status of tissue engineering and regenerative medicine in Iran and related advanced tools: Bioreactors and scaffolds

Because of increased need to tissue and organ transplantation, tissue engineering (TE) researches have significantly increased in recent years in Iran. The present study explored briefly the advances in the TE approaches in Iran. Through comprehensive search, we explored main TE components researches include cell, scaffold, growth factor and bioreactor conducted in Iran. The field of TE and regenerative medicine in Iran dates back to the early part of the 1990 decade and the advent of stem cell researches. During past two decades, Iran was one of leader in stem cell research in Middle East. The next major step in TE was application and fabrication of scaffolds for TE in the early 2000s with focused on engineering bone and nerve tissue. Iranian researchers extensively used natural scaffolds in their studies and hybridized natural polymers and inorganic scaffolds. There are many universities and government research institutes are conducting active research on tissue-engineering technologies. Limitations to TE in Iran include property design and validation of bioreactors. In conclusion, in the last few years, fields of tissue engineering and regenerative medicine such as stem cell technology and scaffolds have progressed in Iran, but one of the biggest challenges for TE is bioreactors researches.

COMPARISON OF TWO TYPES OF BIOREACTORS IN PLANT CELL SUSPENSION CULTURE

-In plant cell culture on large scale,we have studied two types of biore-actors-Airlift reactor and stirred tank reactor-under the same volume and work conditions. It shows that the value of volumetric oxygen transfer coefficient K1a in airlift is a little higher than that in stirred tank reactor at the aeration rate of 0.1~0.3vvm:the mixing time tm in both of them is small respect to the culture period.The shear stress in stirred tank reactor is higher than that in airlift reactor,but its influence is not negative at all. When the value or the shear stress in medium is low-er than a critical value,it will be favorable to the dispersion of cells and promotes the growth of cells.This result is verified in the experiment we have conducted in the airlift reactor and stirred tank reactor.

Analysis of hydrodynamic effects on biofilm thickness in fluidized-bed tapered bioreactors

Fluidized beds in tapered geometries provide advantages such as a broad range of optimum operating conditions.However,the dynamics of the flow inside these bioreactors is significantly more complex,as they promote non-uniform bioparticles distribution.To this end,the CFD technique can give a detailed description of the flow in the bioreator.Hence,the aim of this work is to assess the influence of the hydrodynamic on the steady-state biofilm thickness through numerical simulations of liquid–solid fluidized bed.Two geometries of tapered bioreactors in the operating conditions used to develop biofilms.Simulations were run to solve the two-phase RANS equations using the open-source software OpenFOAM in transient-state.The SST k−ω model was used to estimate the turbulent features of the flow.Velocity and bioparticles distribution inside the reactor were analyzed for different inlet velocities,while bioparticles collision frequency and shear stresses were evaluated for various operating conditions.The comparison between the turbulent kinetic energy and the granular temperature indicated that the fluid flow is more turbulent than the bioparticles movement.The hydrodynamics influence on the steady-state biofilm thickness was assessed,and results led to the conclusion that biofilm is more sensitive to hydrodynamic shear stress than bioparticles collisions.

Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in membrane bioreactors: Principles, methods and applications

The membrane bioreactor(MBR)technology is a rising star for wastewater treatment.The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter(DOM)in the system.Three-dimensional excitation-emission matrix(3D-EEM)fluorescence spectroscopy,a powerful tool for the rapid and sensitive characterization of DOM,has been extensively applied in MBR studies;however,only a limited portion of the EEM fingerprinting information was utilized.This paper revisits the principles and methods of fluorescence EEM,and reviews the recent progress in applying EEM to characterize DOM in MBR studies.We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity,wavelength regional distribution,and spectral deconvolution(giving fluorescent component loadings/scores),and discussed how to use the information to interpret the chemical compositions,physiochemical properties,biological activities,membrane retention/fouling behaviors,and migration/transformation fates of DOM in MBR systems.In addition to conventional EEM indicators,novel fluorescent parameters are summarized for potential use,including quantum yield,Stokes shift,excited energy state,and fluorescence lifetime.The current limitations of EEM-based DOM characterization are also discussed,with possible measures proposed to improve applications in MBR monitoring.

Membrane bioreactors for hospital wastewater treatment: recent advancements in membranes and processes

Discharged hospital wastewater contains various pathogenic microorganisms,antibiotic groups,toxic organic compounds,radioactive elements,and ionic pollutants.These contaminants harm the environment and human health causing the spread of disease.Thus,effective treatment of hospital wastewater is an urgent task for sustainable development.Membranes,with controllable porous and nonporous structures,have been rapidly developed for molecular separations.In particular,membrane bioreactor(MBR)technology demonstrated high removal efficiency toward organic compounds and low waste sludge production.To further enhance the separation efficiency and achieve material recovery from hospital waste streams,novel concepts of MBRs and their applications are rapidly evolved through hybridizing novel membranes(non hydrophilic ultrafiltration/microfiltration)into the MBR units(hybrid MBRs)or the MBR as a pretreatment step and integrating other membrane processes as subsequent secondary purification step(integrated MBR-membrane systems).However,there is a lack of reviews on the latest advancement in MBR technologies for hospital wastewater treatment,and analysis on its major challenges and future trends.This review started with an overview of main pollutants in common hospital wastewater,followed by an understanding on the key performance indicators/criteria in MBR membranes(i.e.,solute selectivity)and processes(e.g.,fouling).Then,an in-depth analysis was provided into the recent development of hybrid MBR and integrated MBR-membrane system concepts,and applications correlated with wastewater sources,with a particular focus on hospital wastewaters.It is anticipated that this review will shed light on the knowledge gaps in the field,highlighting the potential contribution of hybrid MBRs and integrated MBRmembrane systems toward global epidemic prevention.

A fouling suppression system in submerged membrane bioreactors using dielectrophoretic forces

A novel method was developed to suppress membrane fouling in submerged membrane bioreactors. The method is based on the dielectrophoretic （DEP） motion of particles in an inhomogeneous electrical field. Using a real sample ofbiomass as feed, the fouling-suppression performance using DEP with different electrical field intensities （60-160 V） and different frequencies （50-1000 Hz） was investigated. The fouling-suppression performance was found to relate closely with the intensity and frequency of the electrical field. A stronger electrical field was found to better recover the filtrate flux. This is because of a stronger DEP force acting on the biomass par[ides close to the membrane＇s surface. Above an intensity and frequency value of 130 V and 1 kHz, respectively the permeate flux was reduced due to an electrothermal effect.

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors:Effects of sludge properties

In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge <sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.

Research Update on Bioreactors Used in Tissue Engineering

Owing to the paucity of donor organs and their acute rejection by the immune system after transplantation,advanced organ failure is one of the major challenges faced by the medical community.Static culturing used for synthesising tissues and organs cannot simulate the in vivo mechanical and biochemical signals;therefore,such artificial organs fail to maintain effective functional activity following transplantation.Tissue engineering can overcome these hurdles by successfully enabling regeneration of tissues and organs in vitro.Bioreactors are pivotal in the development and generation of engineered biological products.They simulate the in vivo microenvironment of tissue growth while also providing various mechanical stimuli and biochemical signals to stem cells to effectively generate transplantable organs or tissues.Various designs and types of bioreactors,their applications,and future research prospects are summarised,which promote functional tissue engineering.