Thermophilic Bacterial Consortium Research Articles

Metagenomic analysis of a thermophilic bacterial consortium and its use in the bioremediation of a petroleum-contaminated soil

Biodegradation is difficult at high temperatures due to the limited capacity of microorganisms to survive and function outside their optimum temperature range. Here, a thermophilic petroleum-degrading consortium was enriched from compost at a temperature of 55 °C. 16S rDNA and metagenomic techniques were used to analyze the composition of the consortium and the mechanisms of degradation. The consortium degraded 17000 mg total petroleum hydrocarbons (TPHs) L−1 with a degradation efficiency of 81.5% in 14 days. The consortium utilized a range of substrates such as n-hexadecane, n-docosane, naphthalene and pyrene and grew well over a wide range of pH (4–10) and salinity (0–90 g L−1). The hydrocarbon-degrading extremophilic consortium contained, inter alia, (relative abundance >1%) Caldibacillus, Geobacillus, Mycolicibacterium, Bacillus, Chelatococcus, and Aeribacillus spp. Metagenomic analysis was conducted to discover the degradation and environmental tolerance functional genes of the consortium. Two alkane hydroxylase genes, alkB and ladA, were found. A microcosm study shows that the consortium promoted the bioremediation of soil TPHs. The results indicate that the consortium may be a good candidate for the high-temperature bioremediation of petroleum-contaminated soils.

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50–75 °C), pH values of 6∼8, dye concentrations (100–400 mg/L) and salinities (1–5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min−1 mg−1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.

Ability of the Thermophilic Bacteria Triculture Consortium from Mudiak Sapan Hot Springs to Produce Biofuel

Biofuel is an alternative energy to replace fossil fuels. The most popular form of biofuel today is bioethanol. Biofuels are considered as a suitable alternative to fossil fuels because they are more environmentally friendly. Production of bioethanol utilizing thermophilic microorganisms is more profitable because thermophilic microbes generally have the characteristics of being able to use a variety of substrates, low contamination, and resistance to high temperatures. The use of microbial consortia tends to give better results than the use of monoculture isolates to optimize bioethanol yields. The aim of this study was to determine the compatibility and ability of the best thermophilic bacterial triculture consortium from the Mudiak Sapan hot springs in producing biofuel. This research is a descriptive research, to test isolates of a consortium of thermophilic bacteria that produce bioethanol. The results of this study showed that consortium isolates tended to give better results than monoculture isolates. The best thermophilic bacterial triculture consortium from the Mudiak Sapan hot springs in producing biofuels namely MS 12, 17, 18 produced a bioethanol content of 0.863%.

Effects of photostimulation on the catabolic process of xenobiotics

Light biotechnology is a promising tool for enhancing recalcitrant compounds biodegradation. Xenobiotics can cause a significant impact on the quality of the results achieved by sewage treatment systems due to their recalcitrance and toxicity. The optimization of bioremediation and industrial processes, aiming to increase efficiency and income is of great value. The aim of this study was to accelerate and optimize the hydrolysis of Remazol Brilliant Blue R by photo stimulating a thermophilic bacterial consortium. Three experimental groups were studied: control group; LED Group and Laser Group. The control group was exposed to the same conditions as the irradiated groups, except exposure to light. The samples were irradiated in Petri dishes with either a Laser device (λ660 nm, CW, θ = 0.04 cm2, 40 mW, 325 s, 13 J/cm2) or by a LED prototype (λ632 ± 2 nm, CW, θ = 0.5 cm2, 145 mW, 44 s, 13 J/cm2). We found that, within 48-h, statistically significant differences were observed between the irradiated and the control groups in the production of RNA, proteins, as well as in the degradation of the RBBR. It is concluded that, both Laser and LED light irradiation caused increased cellular proliferation, protein production and metabolic activity, anticipating and increasing the catabolism of the RBBR. Being the economic viability a predominant aspect for industrial propose our results indicates that photo stimulation is a low-cost booster of bioprocesses.

Critical evaluation of post-consumption food waste composting employing thermophilic bacterial consortium

Effect of single-function (oil degrading) and multi-functional bacterial consortium with zeolite as additive for post-consumption food waste (PCFW) composting was investigated through assessing the oil content reduction in a computer controlled 20-L composter. Three treatments of PCFWs combined with 10% zeolite were developed: Treatment-2 and Treatment-3 were inoculated with multi-functional (BC-1) and oil degrading bacterial consortium (BC-2), respectively, while T-1 was without bacterial inoculation and served as control. Results revealed that BC-2 inoculated treatment (T-3) was superior to control treatment and marginally better than T-2 in terms of oil degradation. The reduction of oil content was >97.8% in T-3 and 92.27% in T-2, while total organic matter degradation was marginally higher in T-2 (42.95%) than T-3 (41.67%). Other parameters of compost maturity including germination test indicated that T-2 was marginally better than T-3 and significantly enhanced the oily PCFW decomposition and shortened the composting period by 20days.

Biodegradation of low and high molecular weight hydrocarbons in petroleum refinery wastewater by a thermophilic bacterial consortium

ABSTRACTClean-up of contaminated wastewater remains to be a major challenge in petroleum refinery. Here, we describe the capacity of a bacterial consortium enriched from crude oil drilling site in Al-Khobar, Saudi Arabia, to utilize polycyclic aromatic hydrocarbons (PAHs) as sole carbon source at 60°C. The consortium reduced low molecular weight (LMW; naphthalene, phenanthrene, fluorene and anthracene) and high molecular weight (HMW; pyrene, benzo(e)pyrene and benzo(k)fluoranthene) PAH loads of up to 1.5 g/L with removal efficiencies of 90% and 80% within 10 days. PAH biodegradation was verified by the presence of PAH metabolites and evolution of carbon dioxide (90 ± 3%). Biodegradation led to a reduction of the surface tension to 34 ± 1 mN/m thus suggesting biosurfactant production by the consortium. Phylogenetic analysis of the consortium revealed the presence of the thermophilic PAH degrader Pseudomonas aeruginosa strain CEES1 (KU664514) and Bacillus thermosaudia (KU664515) strain CEES2. The consortium was further found to treat petroleum wastewater in continuous stirred tank reactor with 96 ± 2% chemical oxygen demand removal and complete PAH degradation in 24 days.

Improved fermentation performance in an expanded ectopic fermentation system inoculated with thermophilic bacteria

Previous research showed that ectopic fermentation system (EFS) inoculated with thermophilic bacteria is an excellent alternative for cow wastewater treatment. In this study, the effects of thermophilic bacterial consortium on the efficiency and quality of the fermentation process in EFS were evaluated by measuring physicochemical and environmental factors and the changes in organic matter composition. In parallel, the microbial communities correlated with fermentation performance were identified. Inoculation of EFS with thermophilic bacterial consortium led to higher temperatures, increased wastewater requirements for continuous fermentation, and improved quality of the litters in terms of physicochemical factors, security test, functional group analysis, and bacterial community composition. The relationship between the transformation of organic component and the dominant bacteria species indicated that environmental factors contributed to strain growth, which subsequently promoted the fermentation process. The results highlight the great potential of EFS model for wide application in cow wastewater treatment and re-utilization as bio-fertilizer.

Purification and Characterization of Thermostable Cellulase from Consortium XM70 in Terrestrial Hot Spring with Sugarcane Bagasse

Purpose : To better understand the sugarcane bagasse (SCB) degradation process and obtain thermostable cellulase from terrestrial hot spring. Methods : Molecular community structure of the newly selected thermophilic bacterial consortium XM70 was determined using the method of the full-length 16S rRNA library-based analysis. The thermostable CMCase was purified with ion-exchange and gel filtration chromatography. Results : Sequence-based identification of species belonging to the genera, Geobacillus, Desulfotomaculum, Bacillus, Exiguobacterium, Paenibacillus and Enterobacter were identified. The maximal activities of carboxymethyl cellulase (CMCase), filter paper cellulase and β-glucosidase of the consortium XM70 were obtained after incubation at 60 °C and pH 6.0 (4 days), 80 °C and pH 7.0 (2 days) and 70 °C and pH 8.0 (4 days), respectively. The yield of reducing sugars in the culture broth achieved 0.11 g.g -1 dry SCB. An extracellular CMCase from consortium XM70 (XM70-CMCase) was purified 7.9-fold to apparent homogeneity with a recovery of 65.41 % and its molecular mass was about 31.0 kDa. Maximum CMCase activity of the purified XM70-CMCase was 3.77 U/mg at 70 °C and pH 7.0. CMCase activity maintained about its maximal value of 70 % after incubation at 80 °C for 60 min. Conclusion : Due to its high temperature stability, the purified XM70-CMCase may be useful for industrial application such as biofuel, animal feed industry, paper industry and clarification of fruit juices. Keywords : Thermostable cellulase, Sugarcane bagasse, Purification, Characterization, Hot spring

Proteogenomic Analysis of a Thermophilic Bacterial Consortium Adapted to Deconstruct Switchgrass

Thermophilic bacteria are a potential source of enzymes for the deconstruction of lignocellulosic biomass. However, the complement of proteins used to deconstruct biomass and the specific roles of different microbial groups in thermophilic biomass deconstruction are not well-explored. Here we report on the metagenomic and proteogenomic analyses of a compost-derived bacterial consortium adapted to switchgrass at elevated temperature with high levels of glycoside hydrolase activities. Near-complete genomes were reconstructed for the most abundant populations, which included composite genomes for populations closely related to sequenced strains of Thermus thermophilus and Rhodothermus marinus, and for novel populations that are related to thermophilic Paenibacilli and an uncultivated subdivision of the little-studied Gemmatimonadetes phylum. Partial genomes were also reconstructed for a number of lower abundance thermophilic Chloroflexi populations. Identification of genes for lignocellulose processing and metabolic reconstructions suggested Rhodothermus, Paenibacillus and Gemmatimonadetes as key groups for deconstructing biomass, and Thermus as a group that may primarily metabolize low molecular weight compounds. Mass spectrometry-based proteomic analysis of the consortium was used to identify >3000 proteins in fractionated samples from the cultures, and confirmed the importance of Paenibacillus and Gemmatimonadetes to biomass deconstruction. These studies also indicate that there are unexplored proteins with important roles in bacterial lignocellulose deconstruction.

Community dynamics of cellulose‐adapted thermophilic bacterial consortia

Enzymatic hydrolysis of cellulose is a key process in the global carbon cycle and the industrial conversion of biomass to biofuels. In natural environments, cellulose hydrolysis is predominately performed by microbial communities. However, detailed understanding of bacterial cellulose hydrolysis is primarily confined to a few model isolates. Developing models for cellulose hydrolysis by mixed microbial consortia will complement these isolate studies and may reveal new mechanisms for cellulose deconstruction. Microbial communities were adapted to microcrystalline cellulose under aerobic, thermophilic conditions using green waste compost as the inoculum to study cellulose hydrolysis in a microbial consortium. This adaptation selected for three dominant taxa--the Firmicutes, Bacteroidetes and Thermus. A high-resolution profile of community development during the enrichment demonstrated a community transition from Firmicutes to a novel Bacteroidetes population that clusters in the Chitinophagaceae family. A representative strain of this population, strain NYFB, was successfully isolated, and sequencing of a nearly full-length 16S rRNA gene demonstrated that it was only 86% identical compared with other validated strains in the phylum Bacteroidetes. Strain NYFB grew well on soluble polysaccharide substrates, but grew poorly on insoluble polysaccharide substrates. Similar communities were observed in companion thermophilic enrichments on insoluble wheat arabinoxylan, a hemicellulosic substrate, suggesting a common model for deconstruction of plant polysaccharides. Combining observations of community dynamics and the physiology of strain NYFB, a cooperative successional model for polysaccharide hydrolysis by the Firmicutes and Bacteroidetes in the thermophilic cellulolytic consortia is proposed.

Bioleaching of metals from electronic scrap and its potential for commercial exploitation

In this study, ability of moderately thermophilic bacterial consortium to extract metals from electronic scrap was evaluated using shake flasks and lab-scale column reactor. We investigated the effects of having additional energy source (FeS2, S0, FeS2+S0), using different consortia of moderately thermophilic bacteria and washing charge material as a pretreatment. At scrap concentrations of 10%, an adapted consortium of Sulfobacillus thermosulfidooxidans and Thermoplasma acidophilum extracted approximately 85% of Cu, 75% of Al, 80% of Ni and 80% of Zn from pretreated electronic scrap with FeS2+S0 (1%). However, a consortium of S. thermosulfidooxidans and Sulfobacilllus acidophilus, containing FeS2+S0, extracted 90% of Cu, 80% of Al, 82% of Ni and 85% of Zn.During column bioleaching studies of 165days, approximately 74% Zn, 68% Al, 85% Cu, 78% Ni was leached out. The results of the leaching process are significant for understanding how to implement these processes on an industrial scale.

Hydrolytic bacteria in mesophilic and thermophilic degradation of plant biomass

AbstractAdding plant biomass to a biogas reactor, hydrolysis is the first reaction step in the chain of biological events towards methane production. Maize silage was used to enrich efficient hydrolytic bacterial consortia from natural environments under conditions imitating those in a biogas plant. At 55–60°C a more efficient hydrolyzing culture could be isolated than at 37°C. The composition of the optimal thermophilic bacterial consortium was revealed by sequencing clones from a 16S rRNA gene library. A modified PCR‐RFLP pre‐screening method was used to group the clones. Pure anaerobic cultures were isolated. 70% of the isolates were related to Clostridium thermocellum. A new culture‐independent method for identification of cellulolytic enzymes was developed using the isolation of cellulose‐binding proteins. MALDI‐TOF/TOF analysis and end‐sequencing of peptides from prominent protein bands revealed cellulases from the cellulosome of C. thermocellum and from a major cellulase of Clostridium stercorarium. A combined culture of C. thermocellum and C. stercorarium was shown to excellently degrade maize silage. A spore preparation method suitable for inoculation of maize silage and optimal hydrolysis was developed for the thermophilic bacterial consortium. This method allows for concentration and long‐term storage of the mixed culture for instance for inoculation of biogas fermenters.

Characterization and treatability of aerobic bacterial thermophilically treated wastewater by a conventional activated sludge and granular activated carbon

An industrial wastewater that was pretreated by an aerobic thermophilic bacterial consortium (THE) was subjected to additional treatability studies by granular activated carbon (GAC) and a conventional activated sludge (CAS). The removal of dissolved organic carbon (DOC) in both systems was generally found to be similar. While GAC was able to attain better effluent concentrations of toluene and methyl isobutyl ketone (MIBK), the CAS was much more efficient at removing acetone. Furthermore, unlike the GAC, the performance of the CAS was not influenced by the high degree of variability in the influent wastewater. Characterization of the influent thermophilic wastewater using gas chromatography-mass spectroscopy (GC/MS) was performed to quantify the micropollutants as well as to evaluate removal efficiencies from the GAC and CAS systems.