Artificial Microbial Consortia Research Articles

Current Advances in the Biodegradation and Bioconversion of Polyethylene Terephthalate.

Polyethylene terephthalate (PET) is a widely used plastic that is polymerized by terephthalic acid (TPA) and ethylene glycol (EG). In recent years, PET biodegradation and bioconversion have become important in solving environmental plastic pollution. More and more PET hydrolases have been discovered and modified, which mainly act on and degrade the ester bond of PET. The monomers, TPA and EG, can be further utilized by microorganisms, entering the tricarboxylic acid cycle (TCA cycle) or being converted into high value chemicals, and finally realizing the biodegradation and bioconversion of PET. Based on synthetic biology and metabolic engineering strategies, this review summarizes the current advances in the modified PET hydrolases, engineered microbial chassis in degrading PET, bioconversion pathways of PET monomers, and artificial microbial consortia in PET biodegradation and bioconversion. Artificial microbial consortium provides novel ideas for the biodegradation and bioconversion of PET or other complex polymers. It is helpful to realize the one-step bioconversion of PET into high value chemicals.

Evaluation of PET Degradation Using Artificial Microbial Consortia.

Polyethylene terephthalate (PET) biodegradation is regarded as an environmentally friendly degradation method. In this study, an artificial microbial consortium composed of Rhodococcus jostii, Pseudomonas putida and two metabolically engineered Bacillus subtilis was constructed to degrade PET. First, a two-species microbial consortium was constructed with two engineered B. subtilis that could secrete PET hydrolase (PETase) and monohydroxyethyl terephthalate hydrolase (MHETase), respectively; it could degrade 13.6% (weight loss) of the PET film within 7 days. A three-species microbial consortium was further obtained by adding R. jostii to reduce the inhibition caused by terephthalic acid (TPA), a breakdown product of PET. The weight of PET film was reduced by 31.2% within 3 days, achieving about 17.6% improvement compared with the two-species microbial consortium. Finally, P. putida was introduced to reduce the inhibition caused by ethylene glycol (EG), another breakdown product of PET, obtaining a four-species microbial consortium. With the four-species consortium, the weight loss of PET film reached 23.2% under ambient temperature. This study constructed and evaluated the artificial microbial consortia in PET degradation, which demonstrated the great potential of artificial microbial consortia in the utilization of complex substrates, providing new insights for biodegradation of complex polymers.

Inoculation of cellulolytic and ligninolytic microorganisms accelerates decomposition of high C/N and cellulose rich sugarcane straw in tropical sandy soils

Due to the limited functional potential of the microbial decomposer community in tropical sandy soils, a significant proportion of organic inputs with a high C/N ratio and cellulose (CL) content may remain undecomposed. Moreover, high C/N ratio organic input led to N immobilization and suppressed succeeding crop yield. Inoculation of competent microbial decomposers to such soils could constitute a promising approach to overcome this problem, with beneficial effects on soil organic carbon (SOC) accumulation. Therefore, the objectives were (i) to assess the ability of selected cellulolytic and ligninolytic microbial inoculants to promote the decomposition of high C/N ratio and high cellulose inputs in the initial stages after application, using soil enzyme activity measurements, and (ii) to verify the decomposition efficiency of microbial inocula to enhance short-term soil organic carbon (SOC) quantity and quality, using mid-infrared diffuse reflectance Fourier transform spectroscopy (midDRIFTS)-based functional SOC group analysis, integrated with assayed soil enzyme activities. The experiments consisted of 4 treatments: 1) Control (C): no application of organic inputs; 2) Mulch (M): sugarcane straw mulched at a rate of 6.25 tons ha−1; 3) Incorporation (I): sugarcane straw incorporated to soil at a rate of 6.25 tons ha−1; and 4) Incorporation (treatment 3) + inoculation of an artificial microbial consortium (I + MC). Two experiments were conducted i.e. experiment I (field-based micro-plot and litter bag study (32 weeks)) using a randomized complete block design (RCBD) and experiment II (lab-based incubation study (84 days)) using a completely randomized block design (CRD). Sandy soils derived from a farmer's field located in the Khon Kean province (Northeast Thailand) were used. MC was composed of cellulolytic and ligninolytic bacteria (2.2 × 108 CFU g−1 soil) and fungi (1.9 × 106 CFU g−1 soil) with an application rate of 0.1 g kg−1 sugarcane straw. Our results indicated that treatment I + MC led to the highest dry weight loss of sugarcane straw (73%), highest cellulolytic and ligninolytic enzyme activities (β-glucosidase, cellulase, peroxidase, and phenoloxidase), and short-term SOC accumulation. I + MC also showed increased peroxidase and phenoloxidase activities in the early stages of decomposition. Integration of midDRIFTS and enzyme activity analyses demonstrated that in the initial stages of decomposition cellulolytic and ligninolytic enzyme activities enhanced labile SOC components, while in the later stage, cellulolytic and ligninolytic activities enhanced both labile and stable SOC components. In conclusion, farmers may benefit from this approach, but field validation would be needed prior envisioned large-scale application, including the development of formulation and field application processes, evaluated against environmental and economic indicators.

Enhancing Zn and Cd removal from heavy metal-contaminated paddy soil using an artificial microbial consortium

Enhancing Zn and Cd removal from heavy metal-contaminated paddy soil using an artificial microbial consortium

Effect of diurnal temperature range on bioleaching of sulfide ore by an artificial microbial consortium

Temperature is considered to be one of the main factors affecting bioleaching, but few studies have assessed the effects of diurnal temperature range (DTR) on the bioleaching process. This study investigates the effects of different bioleaching temperatures (30 and 40 °C) and DTR on the bioleaching of metal sulfide ores by microbial communities. The results showed that DTR had an obvious inhibitory effect on the bioleaching efficiency of the artificial microbial community, although this effect was mainly concentrated in the early and middle stages (0–18 days) of exposure, gradually decreasing until almost disappearing in the late stage (18–24 days). Extracellular polymeric substance (EPS) analysis showed that DTR did not change the composition of the EPS matrix (humic acid-like substances, polysaccharides and protein-like substances), but had a significant effect on the generative behavior of EPS, inhibiting the secretion of EPS during the early and middle stages of the bioleaching process. However, the continual increase in EPS secretion in the bioleaching system gradually reduced the adverse effects of DTR on mineral dissolution. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy- energy dispersive spectrometry (SEM-EDS) analysis of the bioleached residue showed that DTR had no obvious effect on the mineralogical characteristics of sulfide ore. Therefore, in industrial sulfide ore bioleaching applications, in order to accelerate the artificial microbial community start-up process, temperature control measures should be increased in the bioleaching process to reduce the adverse effects of DTR on mineral dissolution.

The power of two: An artificial microbial consortium for the conversion of inulin into Polyhydroxyalkanoates

One of the major issues for the microbial production of polyhydroxyalkanoates (PHA) is to secure renewable, non-food biomass feedstocks to feed the fermentation process. Inulin, a polydisperse fructan that accumulates as reserve polysaccharide in the roots of several low-requirement crops, has the potential to face this challenge.In this work, a “substrate facilitator” microbial consortium was designed to address PHA production using inulin as feedstock. A microbial collection of Bacillus species was screened for efficient inulinase producer and the genome of the selected strain, RHF15, identified as Bacillus gibsonii, was analysed unravelling its wide catabolic potential. RHF15 was co-cultured with Cupriavidus necator, an established PHA producer, lacking the ability to metabolize inulin. A Central Composite Rotary Design (CCRD) was applied to optimise PHA synthesis from inulin by the designed artificial microbial consortium, assessing the impact of species inoculum ratio and inulin and N-source concentrations. In the optimized conditions, a maximum of 1.9 g L−1 of Polyhydroxybutyrate (PHB), corresponding to ~80% (gpolymer/gCDW) polymer content was achieved. The investigated approach represents an effective process optimization method, potentially applicable to the production of PHA from other complex C- sources.

Consolidated bioprocessing of lignocellulose for production of glucaric acid by an artificial microbial consortium

BackgroundThe biomanufacturing of d-glucaric acid has attracted increasing interest because it is one of the top value-added chemicals produced from biomass. Saccharomyces cerevisiae is regarded as an excellent host for d-glucaric acid production.ResultsThe opi1 gene was knocked out because of its negative regulation on myo-inositol synthesis, which is the limiting step of d-glucaric acid production by S. cerevisiae. We then constructed the biosynthesis pathway of d-glucaric acid in S. cerevisiae INVSc1 opi1Δ and obtained two engineered strains, LGA-1 and LGA-C, producing record-breaking titers of d-glucaric acid: 9.53 ± 0.46 g/L and 11.21 ± 0.63 g/L d-glucaric acid from 30 g/L glucose and 10.8 g/L myo-inositol in fed-batch fermentation mode, respectively. However, LGA-1 was preferable because of its genetic stability and its superior performance in practical applications. There have been no reports on d-glucaric acid production from lignocellulose. Therefore, the biorefinery processes, including separated hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF) and consolidated bioprocessing (CBP) were investigated and compared. CBP using an artificial microbial consortium composed of Trichoderma reesei (T. reesei) Rut-C30 and S. cerevisiae LGA-1 was found to have relatively high d-glucaric acid titers and yields after 7 d of fermentation, 0.54 ± 0.12 g/L d-glucaric acid from 15 g/L Avicel and 0.45 ± 0.06 g/L d-glucaric acid from 15 g/L steam-exploded corn stover (SECS), respectively. In an attempt to design the microbial consortium for more efficient CBP, the team consisting of T. reesei Rut-C30 and S. cerevisiae LGA-1 was found to be the best, with excellent work distribution and collaboration.ConclusionsTwo engineered S. cerevisiae strains, LGA-1 and LGA-C, with high titers of d-glucaric acid were obtained. This indicated that S. cerevisiae INVSc1 is an excellent host for d-glucaric acid production. Lignocellulose is a preferable substrate over myo-inositol. SHF, SSF, and CBP were studied, and CBP using an artificial microbial consortium of T. reesei Rut-C30 and S. cerevisiae LGA-1 was found to be promising because of its relatively high titer and yield. T. reesei Rut-C30 and S. cerevisiae LGA-1were proven to be the best teammates for CBP. Further work should be done to improve the efficiency of this microbial consortium for d-glucaric acid production from lignocellulose.

Spatial Engineering of Microbial Consortium for Long‐Lasting, Self‐Sustaining, and High‐Power Generation in a Bacteria‐Powered Biobattery

AbstractBacteria‐powered biobatteries using multiple microbial species under well‐mixed conditions demonstrate a temporary performance enhancement through their cooperative interaction, where one species produces a resource that another species needs but cannot synthesize. Despite excitement about the artificial microbial consortium, those mixed populations cannot be robust to environmental changes and have difficulty generating long‐lasting power because individual species compete with their neighbors for space and resources. In nature, microbial communities are organized spatially as multiple species are separated by a few hundred micrometers to balance their interaction and competition. However, it has been challenging to define a microscale spatial microbial structure in miniature biobatteries. Here, an innovative technique to design microscale spatial structures with microbial multispecies for significant improvement of the biobattery performance is demonstrated. A solid‐state layer‐by‐layer agar‐based culture platform is proposed, where individual microcolonies separately confined in microscale agar layers form a 3‐D spatial structure allowing for the exchange of metabolites without physical contact between the individual species. The optimized microbial co‐cultures are determined from selected hypothesis‐driven naturally‐occurring bacteria. Vertically and horizontally structured 3‐D microbial communities in solid‐state agar‐based microcompartments demonstrate the practicability of the biobattery, generating longer and greater power in a more self‐sustaining manner than monocultures and other mixed populations.

Increasing biohydrogen production with the use of a co-culture inside a microbial electrolysis cell

Biohydrogen (H2) is considered to be a significant contributor to sustainable economy. However, due to current yields and production rates, large-scale technical implementation of biological H2 production is still a long way off. In this study, two highly productive H2 producers, Enterobacter aerogenes and Clostridium acetobutylicum, were synergistically combined in an artificial microbial consortium (co-culture) for H2 production. Moreover, this co-culture was utilized in a bioelectrochemical system referred to as microbial electrolysis cell, where a small voltage (0.8 V) is applied to enforce H2 production. The experiments were conducted in closed batch mode using cellobiose as carbon source. Each of the applied approaches (co-culture and applied voltage) led to an increase in H2 evolution rate (HER), resulting in a maximum HER of 0.93 mmol L−1 h−1 for the co-culture at an applied voltage of 0.8 V. With the further scale-up and optimization of the examined system parameters, sustainable H2 production for large-scale applications might be feasible within the near future.

Synechocystis Specifically Inhibits Growth of Ralstonia eutropha in an Artificial Microbial Consortium

Petroleum derived plastics are a major contributor to global pollution. There is an urgent need for biodegradable, sustainable plastic alternatives. Cyanobacteria have been studied extensively for photosynthetic production of biofuel precursors including alkanes and free fatty acids. However, large scale production has been slow to emerge from these technologies. Here, we wished to evaluate alternative uses for engineered strains of the cyanobacteria Synechocystis PCC 6803 (6803). We investigated the feasibility of using wild type and fatty acid secreting strains of 6803 to support the growth of Ralstonia eutropha. This organism is capable of producing polyhydroxyalkanoates (PHAs), which can be used in bioplastic production. Traditional feedstocks for R. eutropha include palm oil and other biological precursors that compete with cultivatable land, pitting potential bioplastic production against agricultural demands. Since PHAs are of great interest as plastic alternatives, we co-cultured R. eutropha and 6803 strains in the minimal medium BG-11 in an attempt to create carbon neutral PHA from R. eutropha. Surprisingly, we observed inhibition of R. eutropha growth in co-culture with Synechocystis but not another cyanobacterium suggesting further modification of Synechocystis is necessary for use as a feedstock.

Metabolite-based mutualism enhances hydrogen production in a two-species microbial consortium

Sustainable hydrogen production from renewable and low-cost substrates is very important to mitigate environmental and energy-related issues. Microbial consortia are promising for diverse bioenergy and environmental applications, yet microbial interactions are not fully understood. Here, we present comprehensive investigation on how two species in an artificial microbial consortium, consisting of Bacillus cereus A1 and Brevundimonas naejangsanensis B1, mutually cooperate to achieve an overall enhancement in hydrogen production and starch utilization. In this consortium, strains A1 and B1 secrete α-amylase and glucoamylase that are functionally complementary in starch hydrolysis. Moreover, strain A1 converts starch into lactate as a carbon source and electron donor, supporting the cell growth and hydrogen generation of strain B1. In return, strain B1 produces formate as an electron shuttle to strain A1 to enhance hydrogen production. The co-culture re-directs the overall metabolic flux, facilitates the cell growth, and up-regulates the key genes of hydrogen production and starch hydrolysis.

Increased sedimentation of a Pseudomonas–Saccharomyces microbial consortium producing medium chain length polyhydroxyalkanoates

Abstract Concerns about feasibility, separability, settleability, efficiency once hampered studies on polyhydroxyalkanoates (PHAs) production, which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia. Here, a medium chain length PHAs (mcl-PHAs) producing Pseudomonas–Saccharomyces consortium with xylose as the main substrate was studied. Mcl-PHAs accumulation increased from 12.69 mg·L−1 to 152.3 mg·L−1 without any optimization method. The presence of Saccharomyces cerevisiae, though in a relatively low concentration, improved the sedimentation of cell mass of the mixed culture by 60%. Reasons for better sedimentation of the consortium were complex: first, the length of Pseudomonas putida increased two to three times in the consortium; second, the positive surface charge of P. putida was neutralized by S. cerevisiae; third, the adhesion proteins on the surface of S. cerevisiae interacted with the P. putida.

The long-term effect of uranium and pH on the community composition of an artificial consortium.

In the environment, microorganisms are living in diverse communities, which are impacted by the prevailing environmental conditions. Here, we present a study investigating the effect of low pH and elevated uranium concentration on the dynamics of an artificial microbial consortium. The members (Caulobacter sp. OR37, Asinibacterium sp. OR53, Ralstonia sp. OR214 and Rhodanobacter sp. OR444) were isolated from a uranium contaminated and acidic subsurface sediment. In pure culture, Ralstonia sp. OR214 had the highest growth rate at neutral and low pH and only Caulobacter sp. OR37 and Asinibacterium sp. OR53 grew in the presence uranium. The four strains were mixed in equal ratios, incubated at neutral and low pH and in the presence uranium and transferred to fresh medium once per week for 30 weeks. After 30 weeks, Ralstonia sp. OR214 was dominant at low and neutral pH and Caulobacter sp. OR37 and Asinibacterium sp. OR53 were dominant in the presence of uranium. After 12 weeks, the cultures were also transferred to new conditions to access the response of the consortia to changing conditions. The transfers showed an irreversible effect of uranium, but not of low pH on the consortia. Overall, the strains initially tolerant to the respective conditions persisted over time in high abundances in the consortia.

Bioresources for control of environmental pollution.

Environmental pollution is one of the biggest threats to human beings. For practical reasons it is not possible to stop most of the activities responsible for environmental pollution; rather we need to eliminate the pollutants. In addition to other existing means, biological processes can be utilized to get rid of toxic pollutants. Degradation, removal, or deactivation of pollutants by biological means is known as bioremediation. Nature itself has several weapons to deal with natural wastage and some of them are equally active for eliminating nonnatural pollutants. Several plants, microorganisms, and some lower eukaryotes utilize environmental pollutants as nutrients and some of them are very efficient for decontaminating specific types of pollutants. If exploited properly, these natural resources have enough potential to deal with most elements of environmental pollution. In addition, several artificial microbial consortia and genetically modified organisms with high bioremediation potential were developed by application of advanced scientific tools. On the other hand, natural equilibria of ecosystems are being affected by human intervention. Rapid population growth, urbanization, and industrialization are destroying ecological balances and the natural remediation ability of the Earth is being compromised. Several potential bioremediation tools are also being destroyed by biodiversity destruction of unexplored ecosystems. Pollution management by bioremediation is highly dependent on abundance, exploration, and exploitation of bioresources, and biodiversity is the key to success. Better pollution management needs the combined actions of biodiversity conservation, systematic exploration of natural resources, and their exploitation with sophisticated modern technologies.

Formation of artificial, structured microbial consortia (ASMC) by dielectrophoresis

Artificial microbial consortia with defined internal microstructure (ASMC) were constructed by attracting cells of different microbial species to planar micro-electrodes by dielectrophoresis. Cells of Saccharomyces cerevisiae, Escherichia coli and Micrococcus luteus were deposited between the micro-electrodes sequentially to form layered cell aggregates with defined internal structures. The position of the different micro-organisms on the surface and within the cell layers was controlled by varying the electrode geometry, by introducing the different micro-organisms at different times, and by energising different parts of the electrode structure at different times. The cell arrays were stabilised using UV photopolymerised acrylamide-based hydrogels containing acrylamide and N, N′-methylene-bis acrylamide in the ratio of 15/2.2 (w/w), at a concentration of 5%. Although the viability of S. cerevisiae was only slightly affected after incubation in the monomer solution for 30 min, cells immobilised in the polymerised hydrogel exhibited reduced rates of glucose consumption and ethanol production compared with freely suspended cells, possibly due to diffusional limitation in the relatively thick hydrogels used. The gel-stabilised, structured consortia can either remain on the micro-electrode arrays as a structured biofilm, or they can be removed from the electrodes and used in a suspended form. The artificial, structured microbial consortia could be used to study microbial interactions and to create novel metabolic interactions between micro-organisms.