Mixed Microbial Consortium Research Articles

Combined thermochemical-biotechnological approach for the valorization of polyolefins into polyhydroxyalkanoates: Development of an integrated bioconversion process by microbial consortia

Waste management of persistent polymers such as polyolefins (PO)1 still represents a major challenge, often leading to material loss from the value chain and contributing to plastic pollution. This study investigated an integrated process to valorize PO pyrolysis side stream. PO wax was recovered and used as a feedstock for a microbial bioconversion process. A modified emulsification protocol (using two-surfactants system) allowed the successful dispersion and bioconversion of PO wax without the need of the extra oxidation step. Enrichment of plastic landfill inocula allowed to develop efficient mixed microbial consortia (MMC) able to grow on PO wax. Adaptive laboratory evolution improved 4 times cell growth, leading to 2.6–17.3 times shorter lag phase. The bioconversion process using the adapted MMC was performed in a 2 L-bioreactor with PO wax-emulsified media (10 g L−1) at neutral pH and 20% pO2. 87% of substrate was consumed within 12 h and complete consumption was achieved within 48 h (4 times faster than previously reported). A maximum of 2.95 gCDW L−1of biomass was produced, while the intracellular triglycerides reached a maximum of 105.5 mg L−1 at 30 h. Moreover, the conversion of PO wax into polyhydroxyalkanoates (PHAs) was demonstrated and the production was maximized by statistical optimization. Maximum PHA titer of 384 0.1 mg L−1 was achieved, which represents a 1.5–17 times improvement from previous reports. This integrated thermochemical-biotechnological approach might represent an interesting strategy to valorize and upcycle currently unrecyclable PO-rich mixed plastic waste streams, thus improving the circularity of the plastic sector.

The adsorption and fixation of Cd and Pb by the microbial consortium weakened the toxic effect of heavy metal-contaminated soil on rice

With the rapid development of industry and agriculture, the toxicity and pollution of Cd and Pb in soil and plants are becoming increasingly severe. Microbial remediation is considered an economical and sustainable method for addressing heavy metal ion pollution. This experiment established a microbial consortium capable of efficiently adsorbing and fixing Cd and Pb. The consortium consisted of two isolated strains: the straw-degrading bacterium ZJW-6 (Cellulomonas iranensis) and the phosphate-solubilizing bacterium wj1 (Pseudomonas brassicacearum). The microbial consortium exhibited high resistance to Cd and Pb, resulting in a significant reduction in heavy metal toxicity. The minimum inhibitory concentrations of Cd and Pb for the mixed microbial consortium were 900 mg/L and 2500 mg/L, respectively. Results indicated that within seven days, the microbial consortium’s removal rates of Cd and Pb reached 94.25 % and 74 %, respectively, surpassing the removal abilities of the individual member bacteria. It also enriched the soil organic matter and produced larger aggregates to adsorb more heavy metals (Cd: 3.35 mg/kg, Pb: 86.57 mg/kg). By the 60th day, 91.2 % of Cd and 97.89 % of Pb in the soil rhizosphere had been removed, and the free Cd and Pb in plant tissues were significantly reduced. Soil aggregates, which are the basic units of soil and an important index for measuring soil structure, were improved. The microbial consortium also played a significant role in restoring the soil microbial community, mobilizing the combined action of microorganisms represented by Ramlibacter and Sphingomonas to repair heavy metal pollution and promote plant growth. This provides a new method to bioremediate metal-contaminated soil and enhance the plant growth environment.

One-Pot Biocatalytic Route from Alkanes to α,ω-Diamines by Whole-Cell Consortia of Engineered Yarrowia lipolytica and Escherichia coli.

Metabolically engineered microbial consortia can contribute as a promising production platform for the supply of polyamide monomers. To date, the biosynthesis of long-chain α,ω-diamines from n-alkanes is challenging because of the inert nature of n-alkanes and the complexity of the overall synthesis pathway. We combined an engineered Yarrowia lipolytica module with Escherichia coli modules to obtain a mixed strain microbial consortium that could catalyze an efficient biotransformation of n-alkanes into corresponding α,ω-diamines. The engineered Y. lipolytica strain was constructed (YALI10) wherein the two genes responsible for β-oxidation and the five genes responsible for the overoxidation of fatty aldehydes were deleted. This newly constructed YALI10 strain expressing transaminase (TA) could produce 0.2 mM 1,12-dodecanediamine (40.1 mg/L) from 10 mM n-dodecane. The microbial consortia comprising engineered Y. lipolytica strains for the oxidation of n-alkanes (OM) and an E. coli amination module (AM) expressing an aldehyde reductase (AHR) and transaminase (TA) improved the production of 1,12-diamine up to 1.95 mM (391 mg/L) from 10 mM n-dodecane. Finally, combining the E. coli reduction module (RM) expressing a carboxylic acid reductase (CAR) and an sfp phosphopantetheinyl transferase with OM and AM further improved the production of 1,12-diamine by catalyzing the reduction of undesired 1,12-diacids into 1,12-diols, which further undergo amination to give 1,12-diamine as the target product. This newly constructed mixed strain consortium comprising three modules in one pot gave 4.1 mM (41%; 816 mg/L) 1,12-diaminododecane from 10 mM n-dodecane. The whole-cell consortia reported herein present an elegant "greener" alternative for the biosynthesis of various α,ω-diamines (C8, C10, C12, and C14) from corresponding n-alkanes.

From mec cassette to rdhA: a key Dehalobacter genomic neighborhood in a chloroform and dichloromethane-transforming microbial consortium.

Chloroform (CF) and dichloromethane (DCM) are regulated groundwater contaminants. A cost-effective approach to remove these pollutants from contaminated groundwater is to employ microbes that transform CF and DCM as part of their metabolism, thus depleting the contamination as the microbes continue to grow. In this work, we investigate bioaugmentation culture SC05, a mixed microbial consortium that effectively and simultaneously degrades both CF and DCM coupled to the growth of Dehalobacter. We identified the functional genes responsible for the transformation of CF and DCM in SC05. These genetic biomarkers provide a means to monitor the remediation process in the field.

Bio-Augmentation of S2− Oxidation for a Heavily Polluted River by a Mixed Culture Microbial Consortium

The redox balance of inorganic sulfur in heavily polluted rivers might be disrupted, making sulfur reduction a major metabolic pathway of sulfate-reducing bacteria (SRB), leading to a massive accumulation of S2− and blackening the water bodies. A mixed culture microbial consortium (MCMC) of Citrobacter sp.sp1, Ochrobactrum sp.sp2, and Stenotrophomonas sp.sp3 was used to activate native sulfate-oxidizing bacteria (SOB) to augment the S2− oxidizing process. The results demonstrated that MCMC had a significant sulfur oxidation effect, with 98% S2− removal efficiency within 50 h. The sulfide species varied greatly and were all finally oxidized to SO42−. The mechanism of bio-augmentation was revealed through high throughput sequencing analysis. The MCMC could stimulate and simplify the community structure to cope with the sulfide change. The microorganisms (family level) including Enterococcaceae, Flavobacteriaceae, Comamonadaceae, Methylophilaceae, Caulobacteraceae, Rhodobacteraceae, and Burkholderiaceae were thought to be associated with sulfide metabolism through the significant microbial abundance difference in the bio-treatment group and control group. Further Pearson correlation analysis inferred the functions of different microorganisms: Comamonadaceae, Burkholderiaceae, Alcaligenaceae, Methylophilaceae, and Caulobacteraceae played important roles in S2− oxidization and SO42− accumulation; and Comamonadaceae, Burkholderiaceae, Alcaligenaceae, Methylophilaceae, Caulobacteraceae, Campylobacteraceae, Bacteriovoracaceae, and Rhodobacteraceae promoted the sulfur oxidation during the whole process.

Detoxification of typical nitrogenous heterocyclic compound from pharmaceutical wastewater by mixed microbial consortia

Microbial consortia HY3 and JY3 with high degradation efficiency of 2-Diethylamino-4-hydroxy-6-methylpyrimidine (DHMP) were isolated from aerobic and parthenogenic ponds of DHMP-containing pharmaceutical wastewater, respectively. Both consortia were enriched and reached stable degradation performance with a DHMP concentration of 1500 mg L−1. The DHMP degradation efficiencies of HY3 and JY3 were 95.66% ± 0.24% and 92.16% ± 2.34% under the condition of shaking at 180 r·min−1 and the temperature of 30 °C for 72 h. And the removal efficiencies of chemical oxygen demand were 89.14% ± 4.78% and 80.30% ± 11.74%, respectively. High-throughput sequencing results indicated that three bacterial phyla of Proteobacteria, Bacteroidetes, and Actinobacteria were dominant in both HY3 and JY3, but their dominances varied. At the genus level, the richness of Unclassified Comamonadaceae (34.23%), Paracoccus (14.75%), and Brevundimonas (13.94%) ranked top three in HY3 whereas Unclassified Comamonadaceae (40.80%), Unclassified Burkholderiales (13.81%) and Delftia (13.11%) were dominant in JY3. The metabolites of DHMP degradation by HY3 and JY3 were analyzed in detail. Two pathways for cleavage of the nitrogenous heterocyclic ring were speculated, one of which was identified for the first time in this study.

Lignocellulolytic Microbial Systems and its Importance in Dye Decolourization: A Review

Effluents containing dyes from different industrial sectors pose a serious threat to the environment. Different physicochemical strategies are being carried out in industry to reduce the toxicity of dye-containing waste so that dye-mixed wastewater can be further utilized in agriculture or irrigation purposes in water-scarce areas. But those techniques are economically not feasible. There is an alternative mechanism present in biological systems that are biocatalysts which is eco-friendly, low cost, and sustainable. Lignin peroxidase, Laccase, Manganese peroxidase are oxidoreductase classes of enzymes with the ligninolytic ability and are potential biocatalysts for the degradation of environmental toxicants like dyes. Besides ligninolytic enzymes, cellulase, pectinase are also powerful candidates for dye decolourization. Most interestingly these biocatalysts are found in a variety of microbial monoculture as well as in mixed microbial consortia. The consortia are able to reduce the organic load of dye-containing industrial effluent at a higher rate rather than the monoculture. This article critically reviews the efficacy of lignocellulolytic enzymes in dye decolourization by both monoculture and consortia approaches. In addition, this review discusses the genetically and metabolically engineered microbial systems that contribute to dye decolourization as well as put forward some future approaches for the enhancement of dye removal efficacy.

Metagenomic and Genomic Sequences from a Methanogenic Benzene-Degrading Consortium

Draft and complete metagenome assembled genomes (MAGs) were created from multiple metagenomic assemblies of DGG-B, a strictly anaerobic, stable mixed microbial consortium that degrades benzene completely to methane and CO2. Our objective was to obtain closed genome sequences of benzene-fermenting bacteria to enable the elucidation of their elusive anaerobic benzene degradation pathway.

Microbial electrosynthesis of acetate from CO2 in three-chamber cells with gas diffusion biocathode under moderate saline conditions

The industrial adoption of microbial electrosynthesis (MES) is hindered by high overpotentials deriving from low electrolyte conductivity and inefficient cell designs. In this study, a mixed microbial consortium originating from an anaerobic digester operated under saline conditions (∼13 g L−1 NaCl) was adapted for acetate production from bicarbonate in galvanostatic (0.25 mA cm−2) H-type cells at 5, 10, 15, or 20 g L−1 NaCl concentration. The acetogenic communities were successfully enriched only at 5 and 10 g L−1 NaCl, revealing an inhibitory threshold of about 6 g L−1 Na+. The enriched planktonic communities were then used as inoculum for 3D printed, three-chamber cells equipped with a gas diffusion biocathode. The cells were fed with CO2 gas and operated galvanostatically (0.25 or 1.00 mA cm−2). The highest production rate of 55.4 g m−2 d−1 (0.89 g L−1 d−1), with 82.4% Coulombic efficiency, was obtained at 5 g L−1 NaCl concentration and 1 mA cm−2 applied current, achieving an average acetate production of 44.7 kg MWh−1. Scanning electron microscopy and 16S rRNA sequencing analysis confirmed the formation of a cathodic biofilm dominated by Acetobacterium sp. Finally, three 3D printed cells were hydraulically connected in series to simulate an MES stack, achieving three-fold production rates than with the single cell at 0.25 mA cm−2. This confirms that three-chamber MES cells are an efficient and scalable technology for CO2 bio-electro recycling to acetate and that moderate saline conditions (5 g L−1 NaCl) can help reduce their power demand while preserving the activity of acetogens.

Effect of biofilms on the clogging mechanisms of suspended particles in porous media during artificial recharge

Artificial recharge of groundwater is an effective technology for solving the shortage of water resources. The clogging of porous media is a bottleneck that limits the application of this technology. In this study, percolation experiments in sand columns were conducted to investigate the influence of different types of biofilms on the deposition of suspended particles and clogging evolution during artificial recharge. A unique aspect of this study is the consideration of biofilms coated on porous media when the clogging mechanisms of suspended particles in porous media are explored. At the end of the recharge process, the relative hydraulic conductivity (K’) of the porous media in descending order was Pseudomonas aeruginosa experimental group (PA) > Bacillus subtilis experimental group (BS) > mixed microbial consortium experimental group (MC) > suspended particle only group (SP). The suspended particles in SP- moved more deeply into the sand column than those in BS, PA, and MC. Electron microscopy, high-throughput sequencing, and confocal laser scanning microscopy were used to identify the mechanisms governing clogging evolution under the influence of biofilm existence. The presence of a biofilm not only alters the surface charge and physical roughness of the porous media, but also affects the electrostatic interaction between the porous media and suspended particles. Biofilms combine tightly with suspended particles by binding and adhesion, which can form tight biofilm-particle aggregations. Compared with deposition of particle-only in SP, the biofilm-particle aggregations on the surface of the porous media are more firm. The biofilm coated on the surface of porous media occupied the pore vacancy and narrowed the void space compared with that in clean sand, which induced physical straining. As the thickness of biofilm coated on the sand surface increased, the more suspended particles were deposited on the sand surface in PA. These findings provide insights into clogging under the influence of biofilms and have implications for future field-based artificial recharge.

Techno-economic assessment of microbial electrohydrogenesis integration to the fruit processing industry for hydrogen production

A hypothetical facility connected to a fruit processing plant is created to investigate the techno-economic potential of H2 production from residues and wastewater via electrohydrogenesis in a microbial electrolysis cell (MEC), using mixed microbial consortium obtained from the anaerobic wastewater treatment plant. Thermal pretreatment converts cellulose in the substrate into glucose, and deactivates methanogens present in the consortium. A Rhinohide membrane separates the cathode chamber from the anode chamber of the MEC, which requires an external power supply of 0.6 V. In this study, we determine an economically optimal utilization option for H2 and the by-product CO2 by investigating 6 scenarios. Of the 6 scenarios, the option involving the combustion of H2 in a gas engine to produce electricity and CO2 sale is the most financially feasible. Several economic analyses were performed to identify the cost drivers of the H2 production in the economically optimal scenario. Depending on the electricity cost and CO2 selling price, the financial feasibility of electrohydrogenesis-based H2 production process can be further improved.

Effect of pH, Salinity, Dye, and Biomass Concentration on Decolourization of Azo Dye Methyl Orange in Denitrifying Conditions

A recent study by the current authors found simultaneous decolourization and mineralization of high concentrations of methyl orange (500 mg/L) in an anoxic up-flow reactor in denitrifying conditions. To supplement this work, various batch reactor studies were carried out to study the effect of (i) pH (4 to 9), (ii) salinity (1 g/L NaCl to 10 g/L NaCl), (iii) dye concentration (100 mg/L to 1000 mg/L), (iv) biomass concentration (0.3 g/L to 0.21 g/L); on the process, and (iv) kinetics of decolourization in denitrifying conditions. The adapted mixed microbial consortium, originally sourced from the activated sludge process, was capable to simultaneously remove colour, COD, and NO3−-N under denitrifying conditions, even at high methyl orange (MO) concentrations of 1000 mg/L at 84 h. Although the decolourization was possible for wide ranges of pH, better performance was obtained at alkaline pH levels. The decolourization performance increased when biomass concentration increased and was not affected by salinity up to 10 g/L NaCl. This may have been due to enhanced lyses of biomass at high salt concentrations. Batch kinetic studies showed that the MO decolourization followed first-order kinetics, with a rate constant of 0.0612 h−1. Results of this study may help in the future application of textile effluent treatments, using a high biomass retention reactor in denitrifying conditions with minimum sludge disposal costs.

Transition roadmap for thermophilic carbon dioxide microbial electrosynthesis: Testing with real exhaust gases and operational control for a scalable design

Human activities release more carbon dioxide (CO2) into the atmosphere than the natural process can remove. This study attempts to address the main challenges for the thermophilic (50 °C) bioelectrochemical conversion of CO2 into acetate. First, real gaseous emissions were tested with mixed microbial consortia, which had no substantial influence on production rates (difference of 2.5%). Subsequently, a bench-scale system (TRL 4–5) was designed and launched to control key operational variables. Fixing the current at 1.3 A m−2, CO2 was reduced at a rate of 2.21 kg CO2 kg−1 acetate, while the electricity consumption was 2.07 kWh kg−1, the most efficient value so far. The results suggest that the operation with real effluents is feasible and the proposed design is energy efficient, but the right balance between maximising current densities without compromising the biocompatibility with catalysts will determine the transition from laboratory scale towards its implementation in the market.

Effect of 3-Hydroxyvalerate Content on Thermal, Mechanical, and Rheological Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers Produced from Fermented Dairy Manure.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with various 3-hydroxyvalerate (3HV) contents biosynthesized by mixed microbial consortia (MMC) fed fermented dairy manure at the large-scale level was assessed over a 3-month period. The thermal, mechanical, and rheological behavior and the chemical structure of the extracted PHBV biopolymers were studied. The recovery of crude PHBV extracted in a large Soxhlet extractor with CHCl3 for 24 h ranged between 20.6% to 31.8% and purified to yield between 8.9% to 26.9% all based on original biomass. 13C-NMR spectroscopy revealed that the extracted PHBVs have a random distribution of 3HV and 3-hydroxybutyrate (3HB) units and with 3HV content between 16% and 24%. The glass transition temperature (Tg) of the extracted PHBVs varied between −0.7 and −7.4 °C. Some of the extracted PHBVs showed two melting temperatures (Tm) which the lower Tm1 ranged between 126.1 °C and 159.7 °C and the higher Tm2 varied between 152.1 °C and 170.1 °C. The weight average molar mass of extracted PHBVs was wide ranging from 6.49 × 105 g·mol−1 to 28.0 × 105 g·mol−1. The flexural and tensile properties were also determined. The extracted polymers showed a reverse relationship between the 3HV content and Young’s modulus, tensile strength, flexural modulus, and flexural strength properties.

A slurry electrode based on reduced graphene oxide and poly(sodium 4-styrenesulfonate) for applications in microbial electrochemical technologies

• A slurry electrode was synthesised using reduced graphene oxide. • Electronic percolation was established at a particle loading of only 2% (wt.) • The slurry displayed shear thinning behaviour, which favours upscaling. • Fluidisation enabled 4.7x higher electro-catalytic current production with microbes. A reduced graphene oxide slurry electrode was prepared via electrochemical reduction of graphene oxide, using anionic surfactant poly(sodium 4-styrenesulfonate) to stabilise the suspension. The slurry electrode was characterised for its electrochemical and rheological properties and tested for its application in a microbial electrochemical system under both static and fluidised conditions. Thanks to the high ratio of lateral dimension to thickness, reduced graphene oxide allowed electronic percolation at a particles loading of only 2% (wt.), which is significantly lower than typically applied with other graphitic materials such as activated carbon. The slurry displayed shear thinning behaviour, which is advantageous in real scale applications to guaranteeing homogeneity during fluidisation and to prevent sedimentation under static conditions. When tested under fluidised conditions in a microbial electrochemical device seeded with a mixed microbial consortium, the slurry enabled a 4.7x improvement of catalytic current production compared to static conditions. This approach may represent an important step toward increasing competitiveness and applicability of microbial electrochemical technologies.

Enhancing hydrogen production from winery wastewater through fermentative microbial culture selection

The present paper aims at enhancing the fermentative/co-fermentative hydrogen production from winery wastewater. Winery wastewater is a very abundant waste stream, with a high hydrogen production potential. On the other hand, it might exert toxic effects towards many hydrogen-producing bacteria. To optimize the process, a mixed microbial consortium was subject to microbial analysis to identify hydrogen-producing strains. These latter were isolated to obtain several pure cultures, either dark-fermentative, or photo-fermentative. Comparative fermentation tests were performed, using the isolated pure cultures, the initial mixed culture and a co-culture consisting of the two most performant dark fermentative and photo fermentative strains (i.e. Klebsiella pneumoniae strain MF101 and Rhodopseudomonas sp. strain BR0Y6). Results show that the initial mixed culture led to the highest production of 290 NmLH2 L−1. Further analyses on metabolic intermediates demonstrate the importance of synergies established in open fermentations to enhance the conversion of complex organic substrates to hydrogen.

Utilization of lignocellulosic biofuel conversion residue by diverse microorganisms

BackgroundLignocellulosic conversion residue (LCR) is the material remaining after deconstructed lignocellulosic biomass is subjected to microbial fermentation and treated to remove the biofuel. Technoeconomic analyses of biofuel refineries have shown that further microbial processing of this LCR into other bioproducts may help offset the costs of biofuel generation. Identifying organisms able to metabolize LCR is an important first step for harnessing the full chemical and economic potential of this material. In this study, we investigated the aerobic LCR utilization capabilities of 71 Streptomyces and 163 yeast species that could be engineered to produce valuable bioproducts. The LCR utilization by these individual microbes was compared to that of an aerobic mixed microbial consortium derived from a wastewater treatment plant as representative of a consortium with the highest potential for degrading the LCR components and a source of genetic material for future engineering efforts.ResultsWe analyzed several batches of a model LCR by chemical oxygen demand (COD) and chromatography-based assays and determined that the major components of LCR were oligomeric and monomeric sugars and other organic compounds. Many of the Streptomyces and yeast species tested were able to grow in LCR, with some individual microbes capable of utilizing over 40% of the soluble COD. For comparison, the maximum total soluble COD utilized by the mixed microbial consortium was about 70%. This represents an upper limit on how much of the LCR could be valorized by engineered Streptomyces or yeasts into bioproducts. To investigate the utilization of specific components in LCR and have a defined media for future experiments, we developed a synthetic conversion residue (SynCR) to mimic our model LCR and used it to show lignocellulose-derived inhibitors (LDIs) had little effect on the ability of the Streptomyces species to metabolize SynCR.ConclusionsWe found that LCR is rich in carbon sources for microbial utilization and has vitamins, minerals, amino acids and other trace metabolites necessary to support growth. Testing diverse collections of Streptomyces and yeast species confirmed that these microorganisms were capable of growth on LCR and revealed a phylogenetic correlation between those able to best utilize LCR. Identification and quantification of the components of LCR enabled us to develop a synthetic LCR (SynCR) that will be a useful tool for examining how individual components of LCR contribute to microbial growth and as a substrate for future engineering efforts to use these microorganisms to generate valuable bioproducts.

Green solvent extraction and properties characterization of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biosynthesized by mixed microbial consortia fed fermented dairy manure

The aims of this study were to assess the large-scale extraction and recovery of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biosynthesized by mixed microbial consortia (MMC) that was fed fermented dairy manure at the pilot level using green solvents (ethanol, cyclohexanone (CYC), and dimethyl carbonate (DMC)). The reflux extraction procedure with CYC for 3 h at 130 °C and DMC for 4 h at 90 °C showed the highest recovery (32.3%) with an overall pure yield of 30.0%. A modified Soxhlet extraction process was also evaluated and gave lower crude (18–20%) and purified (12.7–13.8%) PHBV yields. The molar mass of extracted PHBV with DMC in reflux was 7.07 × 105 g·mol−1 which was comparable to the control. The thermal, mechanical, and rheological behavior of extracted PHBV were also examined. Mechanical properties result showed that strength and modulus values of the polymers extracted in the large Soxhlet extractor were lower than those extracted by reflux.

Screening for suitable mixed microbial consortia from anaerobic sludge and animal dungs for biodegradation of brewery spent grain

Lignocellulosic wastes, such as brewery spent grain (BSG), represent valuable resources from a biorefinery perspective, being sources of both chemical and energy production. Improving degradation rates of these recalcitrant feedstocks is a necessity, and bioaugmentation with specialised microbial consortia can be a viable means of achieving this. Six sources of mixed microbial consortia were screened, using biodegradation activity tests, for their capacity to enhance production of both chemicals (volatile fatty acids or ethanol) and energy (biogas) from BSG. The inocula used were anaerobic granular sludge as i) intact granules and ii) crushed granules, iii) bovine rumen fluid, and a number of animal manures including iv) giraffe, v) rhinoceros, and vi) tiger. Amplicon sequencing was used to investigate prokaryotic communities within these inocula on day 0 and day 21. Despite herbivore dung harbouring the largest hydrolytic community, the best solids destruction was achieved using anaerobic granular sludge, either intact (64.8 ± 11.9%) or crushed (63.4 ± 3.7% VS destruction). Granular sludge also resulted in the highest gas production, followed by giraffe manure. Contrastingly, the highest volatile fatty acid accumulation was achieved using rhinoceros and tiger manure, at 3.86 (±0.55) and 3.20 (±0.74) gCOD L−1, respectively. Despite these two manure samples having the highest relative abundances of bacteria associated with cellulose and hemicellulose degradation, they supported the poorest solids destruction, perhaps due to the VFA accumulation therein. Thus, while some inocula aided BSG degradation, further research is required to determine the inhibitors of hydrolysis and therefore BSG degradation.

Bio-Augmentation of S2- Oxidation for a Heavily Polluted River by a Mixed Culture Microbial Consortium

Bio-Augmentation of S2- Oxidation for a Heavily Polluted River by a Mixed Culture Microbial Consortium