Mixed Culture Of Bacteria Research Articles

Novel approach for the treatment of the organic fraction of municipal solid waste: Coupling thermal hydrolysis with anaerobic digestion and photo-fermentation

In this study, two different organic fractions of municipal solid waste (OFMSW) served as raw material in a novel treatment process that combines thermal hydrolysis (TH) pretreatment at different times, followed by anaerobic digestion of the solid fraction and photo-fermentation of the liquid fraction. The results indicate that both wastes performed similarly, and no statistically relevant differences stand out on the overall performance regarding TH times. The thermal pretreatment improves the biodegradability of the solid fraction during anaerobic digestion compensating the loss of the organic matter in the liquid fraction. The produced biogas may feed a combined heat and power (CHP) system, making the process energetically positive in all studied scenarios. In addition, the combination of TH and anaerobic digestion decreased the volume of the waste to be disposed by 59–61%, which is 5–11% higher than that obtained with the traditional treatment of anaerobic digestion process. Specific phototrophic activity tests were performed on the liquid phase using a mixed culture of purple phototrophic bacteria (PPB) that consumed up to 80% of the soluble organics. The assays yielded an average 52% efficiency on specific phototrophic activity (kM) and 62% on biomass yield (YX/S), compared to an optimized growth medium. PPB was also capable of producing polyhydroxyalkanoates, bioH2 and single-cell protein without optimization. Apart from methane, the overall mass balances showed yields up to 150 g of high added-value products per Kg of initial total solids on this proof-of-concept platform.

Potentials of mixed cultures of bacteria in the biodegradation of crude oil

This study aimed at exploring the potentials of mixed cultures of bacteria isolated from crude oil polluted sites for the biodegradation of crude oil. Mixed cultures of five bacterial isolates: Pseudomonas aeruginosa, P. putida, P. fluorescens, Bacillus subtilis and Micrococcus luteus were used for the crude oil biodegradation study. The degrading ability of the mixed cultures were assessed for duration of 28 days on a shaker at 300 rpm and at ambient temperatures (28±2 oC) in a mineral salt broth amended with 1% crude oil. Parameters used to assess the degradative abilities were pH, bacterial load, and residual crude oil contents. The result showed a significant increase in the bacterial count as the biodegradative study progressed while the pH and residual crude oil content decreased. The consortium of P. aeruginosa, P. putida, P. fluorescens, B. subtilis and M. luteus (CB1) was able to achieve reduction of crude oil to 92.4% followed by P. aeruginosa, P. putida, and P. fluorescens (CB2) with reduction of 89.5% in 28 days of biodegradative study. It is concluded from this study that the consortium CB1 were effective crude oil degraders. Thus, they are recommended for use in the bioremediation of polluted soils. Key words: Polluted soils, Crude oil, Consortia, Bacteria, Biodegradation

Biodegradation of LLDPE plastic by mixed bacteria culture of Pseudomonas aeruginosa and Brevibacterium sp.

Plastics take more than 400 years to naturally degrade. This study therefore aims to degrade Linear Low Density Polyethylene (LLDPE) plastic using a mixture of culture bacteria Pseudomonas aeruginosa and Brevibacterium sp. Pieces of LLDPE plastic measuring 1 x 1 cm2, weighing 10 grams are put into containers containing Nutrient Broth (NB) growth media. The biodegradation process is carried out for 30 days with the test parameters being temperature (°C) and acidity (pH). The Gravimetric method was used to determine weight, while Fourier Transform Infrared (FTIR) analysis was used to actuate the morphology, changes in structure and surface of polyethylene. The results showed that mixed bacterial culture has the potential to degrade LLDPE plastic with a removal percentage of 2-7%, which is based on gravimetric analysis at 25°C, acidity value (pH) 7 for 30 days. Therefore, this study proves that mixed bacterial cultures degrades LLDPE plastic by using it as a carbon source.

Continuous process of aerobic biodegradation of beet molasses vinasse: focus on betaine removal

We analyzed the effect of hydraulic retention time (HRT) and pH control of beet molasses vinasse on the efficiency of its continuous aerobic biodegradation with a mixed culture of Bacillus bacteria. Two experimental series were conducted in a 2-L stirred-tank reactor, at an aeration rate of 1 vvm, stirrer speed of 900 rpm, and temperature of 36 °C. The first series was run without medium pH control, whereas the other with pH maintained at 8.0. In both series, HRTs were 26, 47, and 78 h, whereas vinasse pH was raised to 8.0. The extent of its treatment via aerobic biodegradation depended on betaine assimilation phenomenon. High removal of pollutants (over 84%) expressed by the SCODsum index (SCODsum = soluble COD determined with the dichromatic method + theoretical COD of betaine) was achieved at HRTs of 47 and 78 h, whereas medium pH control had no explicit effect on biodegradation efficiency.

Indigenous biosensors for in situ hydrocarbon detection in aquatic environments

Abstract The use of microbial biofilms for the detection of hydrocarbon contamination in aquatic environments was investigated in this study. Two different microbial biofilms consisting of mixed culture bacteria and microalgae were used as biocatalysts and sensing organisms in the anode and cathode chambers of a bioelectrochemical system, respectively. A series of experiments were conducted to evaluate the potential of this method for sensing hydrocarbon contamination and to study the effect of gasoline (varied between 0.04% (v/v) and 1% (v/v)) and background chemical oxygen demand (COD) concentrations on the sensor response. A linear relationship was observed for gasoline concentrations between 0 and 0.1% (v/v), while an exponential relationship was noted for the gasoline concentration in the range of 0 to 1% (v/v). Reproducibility and resilience of the biosensor in detecting the presence of hydrocarbons were studied. Finally, the ability of the biosensor to remove COD (∼70%) indicated its possible use in the bioelectrochemical treatment of polluted waters.

Community Structure Analyses of Anodic Biofilms in a Bioelectrochemical System Combined with an Aerobic Reactor

Bioelectrochemical system (BES)-based reactors have a limited range of use, especially in aerobic conditions, because these systems usually produce current from exoelectrogenic bacteria that are strictly anaerobic. However, some mixed cultures of bacteria in aerobic reactors can form surface biofilms that may produce anaerobic conditions suitable for exoelectrogenic bacteria to thrive. In this study, we combined a BES with an aerobic trickling filter (TF) reactor for wastewater treatment and found that the BES-TF setup could produce electricity with a coulombic efficiency of up to 15% from artificial wastewater, even under aerobic conditions. The microbial communities within biofilms formed at the anodes of BES-TF reactors were investigated using high throughput 16S rRNA gene sequencing. Efficiency of reduction in chemical oxygen demand and total nitrogen content of wastewater using this system was >97%. Bacterial community analysis showed that exoelectrogenic bacteria belonging to the genera Geobacter and Desulfuromonas were dominant within the biofilm coating the anode, whereas aerobic bacteria from the family Rhodocyclaceae were abundant on the surface of the biofilm. Based on our observations, we suggest that BES-TF reactors with biofilms containing aerobic bacteria and anaerobic exoelectrogenic bacteria on the anodes can function in aerobic environments.

Detoxification of Deoxynivalenol by a Mixed Culture of Soil Bacteria With 3-epi-Deoxynivalenol as the Main Intermediate.

Deoxynivalenol (DON) is a widely distributed mycotoxin that frequently occurs in various agricultural raw materials and feeds. DON acts as a virulence factor that accelerates the spread of plant diseases; moreover, its accumulation in grains causes yield loss and serious health problems to humans and livestock. Biodegradation of DON into less- or non-toxic substances using naturally existing microorganisms is considered the best approach for DON detoxification. Although various single isolates and mixed cultures capable of detoxifying DON have been reported, details of the metabolic pathways and the degrading enzymes/coding genes involved are scarce. In this study, we aimed to isolate DON-degrading bacteria from soil samples and explore the mechanisms. Toward this end, 85 soil samples collected from different provinces in China were enriched under aerobic conditions with mineral media containing 50 μg/ml of DON as the sole carbon source. The bacterial consortium LZ-N1 exhibited highly efficient and steady DON-transforming activity. High-throughput sequencing was used to characterize the composition of the involved microflora, and analysis of 16S rRNA sequences indicated that LZ-N1 was composed of at least 11 bacterial genera, with Pseudomonas accounting for nearly half the relative abundance. Coincubation of a mixed culture of two novel strains from the LZ-N1 consortium, namely Pseudomonas sp. Y1 and Lysobacter sp. S1, showed sustained transformation of DON into the metabolite 3-epi-deoxynivalenol, with no degradation products detected after 72 h. The cell-free supernatant, lysate, and cell debris of the mixed culture possessed DON-degrading ability, with the supernatant reaching a DON degradation rate of 100% within 48 h with 50 μg/ml of DON. This is the first report of two-step enzymatic epimerization of DON by a mixed culture, which may provide a new insight into this pathway for future applications in detoxification of DON-contaminated cereals and feed.

Biohydrogen as a renewable energy and its potential production from the conversion of palm oil mill effluent by anaerobic processes

Biohydrogen is one of the promising alternatives to be used as a source of energy in the future. Several studies related to the production of biohydrogen through the process of conversion of organic wastewater by anaerobic process have been done with different reactor conditions. However, biohydrogen is not the main products produced in the process, even biohydrogen is produced in relatively few amounts compared to other acidogenesis products such as volatile acids. The aims of the study are to determine the optimum conditions of biohydrogen production through the control of pH are 5.5; 6.5; 7.5 and 8.5. This factor affects to the metabolism pathway. The study was conducted using the wastewater from the palm oil mill effluent as a substrate, pure culture and mixed culture bacteria as a biomass and performed in the laboratory using an anaerobic batch reactor which will be operated for 72 hours. Sampling was done every 6 hours and then analysed the product of acidogenesis produced. The results show that the optimum conditions for biohydrogen production occurs in the reactor with the pH 5.5-6.5 are 15.27% ± 0.404% to 15.40% ± 0.265%.

Purple Sweet Potato Polyphenols Differentially Influence the Microbial Composition Depending on the Fermentability of Dietary Fiber in a Mixed Culture of Swine Fecal Bacteria.

The prevalence of many chronic diseases which have been associated with poor nutrition may be reduced by the positive modulation of colonic microbiota. In this study, we assess the effects of purple sweet potato polyphenols (PSP) in a mixed culture of swine fecal bacteria during in vitro colonic fermentation using pig colonic digest. Jar fermenters were used to conduct a small scale in vitro colonic fermentation experiments under the anaerobic condition for 48 h. Jar fermenters were assigned to one of the following groups: Cellulose, cellulose + PSP, inulin, and inulin + PSP. The present study revealed that the polyphenolic content of purple sweet potato could modulate the colonic microbiota by differentially increasing the population of beneficial bacteria and decreasing the pathogenic bacteria depending on cellulose and inulin. Accordingly, PSP might be a material conducive for improving the conditions for the fermentation of partly-fermentable dietary fiber. Besides, PSP was also responsible for the drastic reduction of putrefactive products, especially p-cresol to a significant level. Our results suggest that PSP could alter the microbial composition depending upon the fermentability of dietary fiber and has the potential to maintain a stable and healthy colonic environment that will ultimately alleviate chronic diseases development and confer health benefits to the host.

Corrosion behaviour of stainless and carbon steels exposed to sulphate – reducing bacteria from industrial heat exchangers

Corrosion responses of some carbon steels and stainless steel in the presence of a mixed industrial culture of bacteria (referred to as SRB – sulphate – reducing bacteria) found in industrial heat exchangers was studied to recommend best alloys under this service condition. Cooling towers in three plants were studied for SRB presence, and two of the plants showed positive indication of SRB presence based on characteristic hydrogen sulphide odour, media blackening and biofilm presence relative to a control media. Mixed cultures obtained from the plant were thereafter grown in prepared media incubated at 35 °C for 18 days. Open circuit potential and potentiodynamic polarisation studies in anaerobic conditions were done on the selected alloys in aqueous media with and without the grown SRB. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were then used to determine the corrosion morphology and corrosion products formation. The voltamograms show higher icorr for alloys under the SRB compared to the control media, indicating the SRB indeed increased the corrosion rates. The corrosion rates of the alloys were mainly affected by the SRB metabolic activity which produced S2− ions in the media. The surface analysis showed pitting on ASTM A106-B, localised corrosion on ASTM A516-70 and intergranular corrosion on ASTM A179. The EDS analysis supported the findings with higher weight percent of iron and sulphur on ASTM A516-70 due to the presence of iron sulphide. Iron sulphide precipitated on the surface of the specimens to form a passive film. The Tafel plot recorded a corrosion rate of 1.23 mm/year for ASTM A179, 1.08 mm/year for ASTM A516-70, 0.53 mm/year for ASTM A106-B and 0.91 mm/year for duplex stainless steel (2205) when exposed to SRB media. ASTM A516-70 carbon steel was chosen as a better suited material in this environment.

Studies on the Influence of Mixed Culture from Buried Soil Sample for Biodegradation of Sago Starch Filled Natural Rubber Latex Gloves

The addition of sago starch into natural rubber (NR) latex compounds was aimed to accelerate the degradation process of the end products including gloves as an alternative to reduce solid waste disposal problem. In this research work, the degradation of sago starch filled natural rubber (SS/NR) latex gloves by a mixed culture from buried soil sample was investigated. The Gram staining test of mixed culture showed the Gram-negative bacteria are the dominant species as an effective bacterium to degrade the SS/NR latex gloves. The starch hydrolysis test was performed to confirm the existence of starch-degrading bacteria in mixed culture that consume sago starch from the gloves. Based on the biodegradation rate results obtained, the existence of starch-degrading bacteria together with rubber-degrading bacteria were observed, which accelerate the biodegradation of SS/NR latex gloves by 53.68%. Meanwhile, the biodegradation rate for sago starch unfilled natural rubber (control) latex gloves were only 50.31%. Thus, the addition of sago starch has shown an increased in the biodegradation rate, which can be used as alternative method to overcome the solid waste disposal problem.

Effect of Mixed Inoculums Volume and pH on Anti Nutritional Level in Cabbage Fermentation using Saccharomyces cerevisiae and Lactobacillus plantarum

Cabbage (Brassica oleracea var. capitata) that is one of the widely consumed vegetables, contains significant amounts of anti-nutritional components, such as tannin. This component can be reduced by fermentation, where bacterial tannase activity is able to degrade tannin into glucose and gallic acid. A simultaneously mixed cultures fermentation using Saccharomyces cerevisiae and Lactobacillus plantarum has been developed because they possess some mutualism interaction that can be beneficial in the fermentation process. Therefore, this research was focused on the effect of mixed inoculums volume of S. cerevisiae and L. plantarum and initial culture pH on the tannin and glucose level during cabbage fermentation. The sliced cabbage was inoculated with simultaneously mixed cultures (volume ratio of yeast and bacteria used was 1:1) at a different volume range 5%-25% (v/v) and also various pH range from 4 to 7, and then incubated at room temperature in anaerobic condition for 4 days. Tannin and glucose level in fermented cabbage (both biomass and filtrate) were determined using Folin-Denis and phenol-sulphuric method, respectively. The using of 5% mixed inoculums volume and initial pH around 7 were found to be the optimum condition for tannin degradation in cabbage. The remained tannin level in these fermented cabbage decreased up to 18.58% (54.061 mg/100 g FW). This experiment reveals that the amounts of inoculums and initial culture pH affected tannin degradation during cabbage fermentation using mixed cultures of yeast and lactic acid bacteria.

Biodegradation of mixed polycyclic aromatic hydrocarbons by pure and mixed cultures of biosurfactant producing thermophilic and thermo-tolerant bacteria

Applicability of thermophilic and thermo-tolerant microorganisms for biodegradation of polycyclic aromatic hydrocarbons (PAHs) with low water solubility is an interesting strategy for improving the biodegradation efficiency. In this study, we evaluated utility of thermophilic and thermo-tolerant bacteria isolated from Unkeshwar hot spring (India) for biodegradation of four different PAHs. Water samples were enriched in mineral salt medium (MSM) containing a mixture of four PAHs compounds (anthracene: ANT, fluorene: FLU, phenanthrene: PHE and pyrene: PYR) at 37 °C and 50 °C. After growth based screening, four potent strains obtained which were identified as Aeribacillus pallidus (UCPS2), Bacillus axarquiensis (UCPD1), Bacillus siamensis (GHP76) and Bacillus subtilis subsp. inaquosorum (U277) based on the 16S rRNA gene sequence analysis. Degradation of mixed PAH compounds was evaluated by pure as well as mixed cultures under shake flask conditions using MSM supplemented with 200 mg/L concentration of PAHs (50 mg/L of each compound) for 15 days at 37 °C and 50 °C. A relatively higher degradation of ANT (92%- 96%), FLU (83% - 86%), PHE (16% - 54%) and PYR (51% - 71%) was achieved at 50 °C by Aeribacillus sp. (UCPS2) and mixed culture. Furthermore, crude oil was used as a substrate to study the degradation of same PAHs using these organisms which also revealed with similar results with the higher degradation at 50 °C. Interestingly, PAH-degrading strains were also positive for biosurfactant production. Biosurfactants were identified as the variants of surfactins (lipopeptide biosurfactants) based on analytical tools and phylogenetic analysis of the surfactin genes. Overall, this study has shown that hot spring microbes may have a potential for PAHs degradation and also biosurfactant production at a higher temperature, which could provide a novel perspective for removal of PAHs residues from oil contaminated sites.

Membraneless Microbial Fuel Cell: Characterization of Electrogenic Bacteria and Kinetic Growth Model

AbstractThe generation of electricity in a membraneless microbial fuel cell (ML-MFC) was studied using dewatered sludge containing a mixed culture of electrogenic bacteria (EB). The EB acted as a b...

Solubilization of Organics Due to Thermal Hydrolysis Pretreatment and the Shift in Microbial Population in Anaerobic Digestion

A study was conducted to analyze the effect of solubilization due to thermal hydrolysis pretreatment on the microbial population responsible for anaerobic digestion at mesophilic temperature. Metagenomic and microbial population analysis was done on digesters receiving sludge with and without thermal hydrolysis pretreatment. The digester receiving thermal hydrolysis pretreatment was stable at lower detention times and showed a shift in microbial population with predominance of methane-producing population in comparison to conventional digesters receiving no thermal hydrolysis pretreatment. Among methanogens, Methanosarcina showed dominance in the thermal hydrolysis pretreatment digester. Digesters with no thermal hydrolysis pretreatment had a mixed culture of acid-producing bacteria and methane-producing archaea, with almost equal proportion of methane-producing Methanobacterium and Methanosarcina. Kinetic parameters showed high growth and substrate utilization rates in digester receiving thermal hydrolysis pretreatment. This article is protected by copyright. All rights reserved.

Microbial fuel cells coupled with the bioleaching technique that enhances the recovery of Cu from the secondary mine tailings in the bio‐electrochemical system

Improper management of dumped tailings not only causes a potential waste of resources but also poses a direct threat to the lives of local residents. A dual‐chamber microbial fuel cell (MFC) combining with the bioleaching technique was used in the study to extract Cu from the secondary mine tailings at a fed‐batch scale. A mixed culture of acidophilic bacteria was enriched and isolated from the acidic drainage in a copper mine. The effects of the pulp densities and initial pH on both the bio‐electronic performances and the recoveries of Cu on bio‐electrochemical platform were comparatively investigated. An appropriate increase in the pulp densities and a suitable decrease in the initial pH facilitated increases in power generations and enhanced the recoveries of Cu from the tailing samples. The maximum power density of 30.54 mW/m2 was achieved in the coupling system with the coulomb efficiency of 4.52%, and the internal resistance of 166.58 Ω being synchronously obtained. Correspondingly, the highest recovery efficiency of Cu of 78.72% was got in the two‐dimensional tests under conditions including the pulp density (w/v) of 20% and the initial pH of 1.8. The electrochemical reduction and the chemical precipitation in MFCs were confirmed as two of main mechanisms in obviously influencing the recovery of Cu. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

Electron transfer interpretation of the biofilm-coated anode of a microbial fuel cell and the cathode modification effects on its power

Biofilm-coated electrodes and outer cell membrane-mimicked electrodes were examined to verify an extracellular electron transfer mechanism using Marcus theory for a donor–acceptor electron transfer. Redox couple-bound membrane electrodes were prepared by impregnating redox coenzymes into Nafion films on carbon cloth electrodes. The electron transfer was believed to occur sequentially from acetate to nicotinamide adenine dinucleotide (NAD), c-type cytochrome, flavin mononucleotide (FMN) (or riboflavin (RBF)) and the anode substrate. Excellent polarisation and power density characteristics were contributed by the modification of the cathode with a high-surface-area ordered mesoporous carbon or a hollow core–mesoporous shell carbon. The maximum power density of the microbial fuel cell (MFC) could be improved by a factor of two mainly due to the accelerated electron consumption by modifying the cathode surfaces within three-dimensionally interconnected mesoporous carbon particles, and the anode was coated with a mixed culture of anaerobic bacteria.

English

This paper presents the biodegradation of pyrene (C16H10), a four-benzene-ring polycyclic aromatic hydrocarbon (PAHs) using a mixed culture of bacteria. The mixed culture was enriched from hydrocarbon-polluted soil sample, using a plate incubated with a thin film of pyrene. The isolates were identified biochemically as Bacillus cereus and Enterobacter aerogenes. The mixed culture bacteria degraded approximately 90% of the pyrene in aqueous medium within six days of incubation. The assessment of other environmental factors necessary for the activity of the mixed culture revealed that the mixed culture grows well between pH of 5.0-7.0 and temperatures of between 20-30°C. From the results of this trial therefore, it is suggested that the mixed culture has good potential for bioremediation applications. Key words: Pyrene, biodegradation, mixed culture, polycyclic aromatic hydrocarbon (PAHs), environmental factors.

Insights on the resistance, capacitance and bioelectricity generation of microbial fuel cells by electrochemical impedance studies

Electrochemical Impedance Spectroscopy is employed to understand the role of anodic capacitance and individual component resistance in the bioelectricity generation of microbial fuel cells.The anodic capacitance during initial bacterial growth and biofilm formation (1–9 days) is 6 times higher than the literature data.The power density calculated on day 24 being 0.497 W/m2 which is approximately 3 times higher than the literature data.The maximum columbic efficiency obtained is 30.8% which is 2.8 times higher than literature. These results demonstrate that the mixed culture bacteria is more efficient in bioelectricity generation in microbial fuel cells and the anodic capacitance due to biofilm growth on anode plays an important role in the power generation of microbial fuel cells. The electrode resistance dominates over solution resistance due to Hydrogen Evolution and Oxygen Reduction Reactions.

Aspen Plus Simulation Strategies Applied to the Study of Chitin Bioextraction from Shrimp Waste.

SUMMARYChitin is an aminopolysaccharide of industrial interest commonly obtained from shrimp processing waste through chemical or biotechnological means. Current environmental concerns offer a stimulating perspective for chitin bioextraction with lactic acid bacteria since a considerable reduction in the use of corrosive and pollutant products is possible. Nevertheless, the efficiency of this bioprocess is still a matter of discussion. In this work, the experimental studies of chitin bioextraction from Pacific white shrimp (Litopenaeus vannamei) waste with a mixed culture of Lactobacillus plantarum, Lactobacillus bulgaricus and Streptococcus thermophilus are used in process simulation using Aspen Plus software for the analysis of the potential application of a bioprocess on plant scale. The experimental results of characterization in shake flasks and 1-litre bioreactor indicated that 50 h of fermentation with the mixed culture of lactic acid bacteria was enough to extract more than 90% of minerals and proteins from the shrimp waste. The use of experimental parameters in the simulation allowed a reliable representation of the bioprocess yielding normalized root mean square values below 10%. Simulation was used for the assessment of the impact of the raw material variability on the production costs and gross margin. In this regard, the gross margin of the operation ranged from 42 to 52% depending on the raw material composition and product yield.