Microbial Bioremediation and Different Bioreactors Designs Applied

Microbial remediation of pollutants involves the use of microorganisms to degrade pollutants either completely to water and carbon dioxide (for organic pollutants) or into less toxic forms. In the case of nonbiodegradable inorganic compounds, bioremediation takes the form of bioaccumulation or conversion of one toxic species to a less toxic form for example Cr(VI) is converted to less toxic (III). Bioremediation is considered an environmentally friendly way for pollution clean-up. Microbial clean up can be applied in situ (in place of contamination) or ex situ (off the site of contamination). In situ remediation in the natural environment is deemed slow and often times difficult to control and optimize the different parameters affecting the bioremediation. To this end, use of engineered bioreactors is preferred. Engineered bioreactors providing for optimum conditions for microbial growth and biodegradation have been developed for use in bioremediation processes to achieve the different desired remediation goals. Bioreactors in use range in mode of operation from batch, continuous, and fed batch bioreactors and are designed to optimize microbial processes in relationship to contaminated media and nature of pollutant. Designed bioreactors for bioremediation range from packed, stirred tanks, airlift, slurry phase, and partitioning phase reactors amongst others

Nonlinear Vibrational Analysis of Nanobeams Embedded in an Elastic Medium including Surface Stress Effects

Due to size-dependent behavior of nanostructures, the classical continuum models are not applicable for the analyses at this submicron size. Surface stress effect is one of the most important matters which make the nanoscale structures have different properties compared to the conventional structures due to high surface to volume ratio. In the present study, nonlinear free vibrational characteristics of embedded nanobeams are investigated including surface stress effects. To this end, a thin surface layer is assumed on the upper and lower surfaces of the cross section to separate the surface and bulk of nanobeams with their own different material properties. Based on harmonic balance method, closed-form analytical solution is conducted for nonlinear vibrations to obtain natural frequencies of embedded nanobeams with and without considerations of surface elasticity and residual surface tension effects corresponding to the various values of nondimensional amplitude, elastic foundation modulus, and geometrical variables of the system. Selected numerical results are given to indicate the influence of each one in detail

Screening and evaluation of some green algal strains (Chlorophyceae) isolated from freshwater and soda lakes for biofuel production

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An assessment of the physicochemical properties and toxicity potential of carwash effluents from professional carwash outlets in Gauteng Province, South Africa

The assessment of the quality of carwash effluents has received scant attention as a potential source of public and environmental health hazard in South Africa as demonstrated by the lack of literature in this subject. The physicochemical quality and potential ramifications of carwash effluents on receiving waterbodies were investigated in this study. Grab effluent samples were collected from six carwash outlets in Gauteng Province of South Africa and analysed for selected physicochemical qualities including biological oxygen demand (BOD), oil and grease, total petroleum hydrocarbons-gasoline range organics (TPH-GRO), pH, dissolved oxygen (DO), total solids (TS) and total dissolved solids (TDS), electrical conductivity (EC), nutrients (nitrates, nitrites and phosphates), anionic surfactants and heavy metals (zinc [Zn], copper [Cu], lead [Pb] and chromium [Cr]). Further, the toxicity potential of the effluent samples was assessed using organisms from four trophic levels ranging from Selenastrum capricornutum (primary producer), Daphnia magna (primary consumer), Poecilia reticulata (secondary-tertiary consumer) and Vibrio fischeri (decomposer). High pollutant levels were observed in all effluents with BOD ranging from 27±2.1 to 650±4.9 mg/l, TDS from 362±8.5 to 686±8.5 mg/l, GRO-TPH from 0.01±0.0 to 7.6±0.2 mg/l, DO from 0.0 to 0.1 mg/l, Zn from 0.79±0.08 to 20±2.12 mg/l, Cu from 0.77±0.03 to 13±0.71 mg/l and oil and grease from 12±2.8 to 43±2.1 mg/l. Ammonium concentrations ranged from 0.4±0.1 to 75±6.4 mg/l; turbidity from 109±0.7 to 4000±29.7 mg/l, anionic surfactants from 1.4±0.1 to 5.8±0.3 mg/l and TPH from < 0.01 to 7.6 mg/l. Toxicity assessment assays resulted in 100% mortality for fish and Daphnia after 96 and 24 h respectively and significant bioluminescence and growth reduction in Vibrio fischeri and algae after 15 min and 72 h respectively. Most of the measured physicochemical parameters were in concentrations above the Environmental Management Agency (EPA) stipulated guidelines. Additionally, the effluents demonstrated acute toxicity against all four test species.UNISA-WiREnvironmental Science

Co-products in maize-soybean growing-pig diets altered in vitro enzymatic insoluble fibre hydrolysis and fermentation in relation to botanical origin

The study examined the effects of botanical factors and fermentation-based, high-level dilution of co-product feeds in maize–soybean growing-pig diets on enzymatic insoluble fibre hydrolysis and fermentation. Feed insoluble fibre residues that were recovered after pepsin-pancreatin digestion were subjected to Roxazyme® G2 (Roxazyme) versus Viscozyme L® V2010 (control) hydrolysis, and to 64-hour fermentation using pig faecal inoculum. The control diet was a 13 MJ metabolizable energy, 141 g total dietary fibre/kg dry matter maize-meal/hominy chop-soybean diet, which was diluted with maize cob, soybean hulls, barley brewer’s grains, lucerne hay or wheat bran in 12 MJ metabolizable energy, 246 g total dietary fibre/kg dry matter iso-nutrient, single co-product test diets. Fermentable insoluble fibre was employed in a computerized iterative selection of ingredients in two iso-nutrient 11 MJ metabolizable energy 319 total dietary fibre/kg dry matter mixed fibre test diets for maximal contrast (high (HF) versus low (LF)) in fermentability. Insoluble fibre extractive pepsin-pancreatin digestibility differed between feed ingredients, and the single co-product test diets, and between the HF and LF mixed co-product diets. Fibre digestibility depended on both the origin and enzyme, with interaction, whereby carbohydrases expressed similar low (0.04 - 0.05) insoluble fibre digestibility for maize cob, moderate (0.12) digestibility for wheat bran and brewer’s grain, with inferior Roxazyme G2 digestibility for maize hominy chop (0.02 vs 0.10) and meal (0.04 vs 0.16), dehulled soybean meal (0.02 vs 0.17), lucerne hay (0.08 vs 0.18), and soybean hulls (0.05 vs 0.33). Co-product-enzyme affinities were expressed in single fibre diets. Low Roxazyme-basal fibre affinity limited its comparative single co-product (0.03 - 0.07 vs 0.16 - 0.22) HF (0.07 vs 0.17) and LF (0.4 vs 0.20) dietary fibre digestibility. Screening for HF/LF did not affect enzymatic digestion, though enzyme combination increased HF, but not LF digestibility. Gas and short chain fatty acid production predicted fermentability proportionately in the declining order of dehulled soybean ≥ maize ≥ soy hulls ≥ maize hominy chop &gt; wheat bran &gt;lucerne hay ≥ brewer’s grain = maize cob. Induced HF and LF contrast was significant. Co-product fibre enrichment decreased fermentability for all except the soy hull and HF diets. Cereal fibre yielded proportionately less acetate, with more propionate and butyrate, and a greater butyrate shift for maize fibre. The HF fibre induced more ACE and less butyrate. Biomarkers of deleterious proteolytic fermentation were high for lucerne (iso-butyrate) and soy hulls (iso-valerate). In conclusion, high-level and fermentation based co-product feed dilution into maize-soybean growing pig diets altered enzymatic insoluble fibre hydrolysis and fermentation in relation to botanical origin. Roxazyme expressed weak hydrolytic potency on maize and soybean insoluble fibre.Keywords: fermentation gas, fermentation kinetics, fibre fermentability, insoluble non-starch polysaccharides, non-starch polysaccharide degrading enzymes, proteolytic fermentation, short-chain fatty acid

Pathogen infection influences a distinct microbial community composition in sorghum RILs

AIMS: The rhizosphere microbiome substantially affects plant health, yet comparatively little is known regarding the foliar community dynamics. Here, we examine the relationship between the microbiota and their response to natural infection by pathogens. METHODS: We established an experimental system using a set of sorghum recombinant inbred lines (RILS). These RILS included four models denoted as resistant, moderately resistant, susceptible and highly susceptible. A combination of 16S rRNA and ITS gene amplicon approaches was used to assess bacteria and fungi, respectively, in foliar samples. RESULTS: We show that the foliar microbiome differs substantially in asymptomatic and symptomatic RILs subsequent to natural infection by pathogens. A significant association was found between plant health and microbial community structure. Our analyses revealed several distinct fungal and bacterial pathogens. These pathogens included Gibberella and Pantoea genera, which were associated with the highly susceptible group. In addition to these pathogens, we also found signatures for Ascochyta, a known plant pathogenic genus. Members of the bacterial genus Methylorubrum and the fungal genus Hannaella, both known to exhibit plant growthpromoting (PGP) traits, were associated with the resistant and moderately resistant groups. These data also reveal numerous highly diverse fungal and bacterial taxa in RILs that did not show symptoms. We also found taxonomic differences between the microbiota hosted by the symptomatic and asymptomatic RILs. CONCLUSIONS: Together, these data suggest that pathogen infection may result in distinct microbiota. These results suggest that highly diverse microbiome may promote the plants ability to resist the effects of pathogens potentially contributing to plant health.The National Research Foundation, the Agricultural Research Council and the University of South Africa.http://link.springer.com/journal/11104pm2022BiochemistryGeneticsMicrobiology and Plant Patholog

An evaluation of the bacterial diversity at Tshipise, Mphephu and Sagole hot water springs, Limpopo Province, South Africa

Tshipise, Mphephu and Sagole are thermal hot water springs in the Limpopo Province of South Africa with temperatures of 58, 43 and 45°C; and pH of 8.85, 8.08 and 9.70, respectively. The bacterial diversity of the hot water springs was determined by pyrosequencing of the two 16S rRNA hypervariable regions V1-3 and V4-7. Analyses of the community DNA revealed that bacterial populations as detectable by the V1-3 or V4-7 region, respectively were dominated by the Bacteriodetes and Proteobacteria for Mphephu, and Proteobacteria and Cyanobacteria for both Tshipise and Sagole. The major differences in the bacterial diversity between the springs was that no Cyanobacteria were detected for Mphephu and the level of Bacteriodetes detected for both Tshipise and Sagole was much lower compared to the levels detected at Mphephu. The Firmicutes were detected at all the springs but at a much lower abundance compared to the other main phyla detected. Various other phyla were detected at the hot springs at levels below 0.20% of the total sequences obtained. It is interesting that very diverse bacterial genera exist in the three hot water springs studied.This research was supported through a grant from Water Research Commission (WRC, SA, Project K5/1959/1).http://www.academicjournals.org/AJM

Improving the bioremediation of phenolic wastewaters by Trametes versicolor

The successful bioremediation of a phenolic wastewater by Trametes versicolor was found to be dependent on a range of factors including: fungal growth, culture age and activity and enzyme (laccase) production. These aspects were enhanced by the optimisation of the growth medium used and time of addition of the pollutant to the fungal cultures. Different media containing ‘high’ (20 g/L), ‘low’ (2 g/L) and ‘sufficient’ (10 g/L) concentrations of carbon and nitrogen sources were investigated. The medium containing both glucose and peptone at 10 g/L resulted in the highest Growth Related Productivity (the product of specific yield and μ) of laccase (1.46 Units of laccase activity)/gram biomass/day and was used in all further experiments. The use of the guaiacol as an inducer further increased laccase activity 780% without inhibiting growth; similarly the phenolic effluent studied boosted activity almost 5 times. The timing of the addition of the phenolic effluent was found to have important consequences in its removal and at least 8 days of prior growth was required. Under these conditions, 0.125 g phenol/g biomass and 0.231 g o-cresol/g biomass were removed from solution per day

A genomic catalog of Earth’s microbiomes

The reconstruction of bacterial and archaeal genomes from shotgun metagenomes has enabled insights into the ecology and evolution of environmental and host-associated microbiomes. Here we applied this approach to >10,000 metagenomes collected from diverse habitats covering all of Earth’s continents and oceans, including metagenomes from human and animal hosts, engineered environments, and natural and agricultural soils, to capture extant microbial, metabolic and functional potential. This comprehensive catalog includes 52,515 metagenome-assembled genomes representing 12,556 novel candidate species-level operational taxonomic units spanning 135 phyla. The catalog expands the known phylogenetic diversity of bacteria and archaea by 44% and is broadly available for streamlined comparative analyses, interactive exploration, metabolic modeling and bulk download. We demonstrate the utility of this collection for understanding secondary-metabolite biosynthetic potential and for resolving thousands of new host linkages to uncultivated viruses. This resource underscores the value of genome-centric approaches for revealing genomic properties of uncultivated microorganisms that affect ecosystem processes