Composting as a solution to the increasing generation of municipal solid waste (MSW), also contribute to GHGs emission when not controlled and could lack some basic nutrients, especially nitrogen. This study assessed ...Composting as a solution to the increasing generation of municipal solid waste (MSW), also contribute to GHGs emission when not controlled and could lack some basic nutrients, especially nitrogen. This study assessed the split-additions of nitrogen-rich substrate to composting materials and their effect on GHGs emissions as well as the quality of the composts. Nitrogen-rich substrates formulated from pig and goat manure were co-composted with MSW for a 12-weeks period by split adding at mesophilic (˚C) and thermophilic (>50˚C) stages in five different treatments. Representative samples from the compost were taken from each treatment for physicochemical, heavy metals and bacteriological analysis. In-situ CH<sub>4</sub>, CO<sub>2</sub>, N<sub>2</sub>O gas emissions were also analyzed weekly during composting. It was observed that all the treatments showed significant organic matter decomposition, reaching thermophilic temperatures in the first week of composting. The absence affects the suitable agronomic properties. All nitrogen-rich substrate applied at thermophilic stage (Treatment two) recorded the highest N, P and K concentrations of 1.34%, 0.97% and 2.45%, respectively with highest nitrogen retention. In terms of GHG emissions, CO<sub>2</sub> was highest at the thermophilic stage when N-rich substrate was added in all treatment, while CH<sub>4</sub> was highest in the mesophilic stage with N-rich substrate addition. N<sub>2</sub>O showed no specific trend in the treatments. Split addition of the N-rich substrate for co-composting of MSW produced compost which is stable, has less nutrient loss and low GHG emissions. Split addition of a nitrogen-rich substrate could be an option for increasing the fertilizer value of MSW compost.展开更多
Mesophilic Argonautes(Agos)from microbial resources have received significant attention due to their potential applications in genome editing and molecular diagnostics.This study characterizes a novel Ago from Pseudob...Mesophilic Argonautes(Agos)from microbial resources have received significant attention due to their potential applications in genome editing and molecular diagnostics.This study characterizes a novel Ago from Pseudobutyrivi-brio ruminis(PrAgo),which can cleave single-stranded DNA using guide DNA(gDNA).PrAgo,functioning as a multi-turnover enzyme,effectively cleaves DNA using 5′-phosphate gDNA,14-30 nucleotides in length,in the presence of both Mn2+and Mg2+ions.PrAgo demonstrates DNA cleavage activity over a broad pH range(pH 4-12),with optimal activity at pH 11.As a mesophilic enzyme,PrAgo cleaves efficiently DNA at temperatures ranging from 25 to 65°C,particularly at 65°C.PrAgo does not show strong preferences for the 5′-nucleotide in gDNA.It shows high tolerance for single-base mismatches,except at positions 13 and 15 of gDNA.Continuous double-nucleotide mismatches at positions 10-16 of gDNA significantly reduce cleavage activity.Furthermore,PrAgo mediates DNA-guided DNA cleavage of AT-rich double stranded DNA at 65°C.Additionally,molecular dynamic simulations suggest that interactions between the PAZ domain and different nucleic acids strongly influence cleavage efficiency.These findings expand our understanding of Protokaryotic Agos and their potential applications in biotechnology.展开更多
Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic a...Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide （BAA）-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.展开更多
The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recover...The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recoveries in a bioleaching process was investigated.Three main bioleaching parameters,namely pH,solid concentration and inoculum percent,were changed during the bioleaching tests based on CCD.The ranges of the bioleaching process variables used in the design were as follows：pH1.46-2.14,solid concentration 0.95%-11.05%,and inoculum percent 1.59%-18.41%.A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix.Empirical model equations were developed according to the copper,molybdenum and rhenium recoveries obtained with these three parameters.Model equations of responses at the base of parameters were achieved by using statistical software.The model equations were then individually optimized by using quadratic programming to maximize copper,molybdenum and rhenium recoveries individually within the experimental range.The optimum conditions for copper recovery were pH 1.68,solid concentration 0.95% and the inoculum 18.41%（v/v）,while molybdenum and rhenium recoveries were 2.18% and 24.41%,respectively.The predicted values for copper,molybdenum and rhenium recoveries were found to be in good agreement with the experimental values.Also jarosite formation during bioleaching tests was also investigated.展开更多
Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate.Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor.The shake flask tests ...Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate.Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor.The shake flask tests were performed with different inoculum size,solids density,pH.and temperature in order to identify optimum conditions.The highest amount of copper elimination,75%was obtained with extreme thermophilic microorganisms(at 12%inoculation,10%solids,65℃and a pH of 1.5).The highest copper elimination by mesophilic microorganisms was 55%(at 12%inoculation,5%solids,30℃at pH 2).The optimum conditions in shake flask tests were applied to 7 days batch tests in a50-L bioreactor.Extreme thermophilic experiment gave the best copper elimination of 60%(at 12%inoculation,10%solids,65℃and pH 1.5).Mesophilic test removed 50%of the copper(at 12%inoculation,10%solids,35℃at pH 2).展开更多
Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flo...Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flow rate of 3.12 L·m-2·h-1 and pH 1.5 passed through each column continuously for 90 d. In the first and the second column, bioleaching was performed without agglomeration of the ore and on the agglomerated ore, respectively. 28wt% of the copper was extracted in the first column after 40 d, while this figure was 38wt% in the second column. After 90 d, however, the overall extractions were almost the same for both of them. Bioleaching with mesophilic bacteria was performed in the third column without agglomeration of the ore and in the fourth column on the agglomerated ore. After 40 d, copper extractions in the third and the fourth columns were 62wt% and 70wt%, respectively. Copper extractions were 75wt% for both the columns after 90 d. For the last column, bioleaching was performed with moderate thermophilic bacteria and agglomerated ore. Copper extractions were 80wt% and 85wt% after 40 and 90 d, respectively. It was concluded that crushing and agglomeration of the ore using bacteria could enhance the copper extraction considerably.展开更多
In this work, low-grade copper sulfide mine has been treated by the bioleaching process using native cultures of Acidithiobacillus ferrooxidans. The bioleaching experiments were carded out in shake flasks at pH 2.0, 1...In this work, low-grade copper sulfide mine has been treated by the bioleaching process using native cultures of Acidithiobacillus ferrooxidans. The bioleaching experiments were carded out in shake flasks at pH 2.0, 180 r.min^-1 and 30℃ for mesophilic bacteria The conductivity of copper bioleaching liquid was determined by the electric conductivity method at temperatures ranging from 298 K to 313 K. The ionic activity coefficients were estimated using Debye-Hucker and Osager-Falkenlagen equations. Meanwhile, the effects of temperature and concentrtion on the mean ionic activity coefficients were discussed. The relative partial molar free energies, enthalpies and entropies of copper teaching solution at above experimental temperatures were calculated. The behaviors of change of relative partial molar quantities were discussed on the basis of electrolytic solution theory. Simultaneously, the thermodynamic characters of bioleaching solution with and without mesophilic bacteria were compared. The existence of mesophilic bacteria changed the Fe^3＋/Fe^2＋ ratio, which resulted in the difference of ionic interaction. The experimental data show that the determination of the thermodynamic properties during the bioleaching processes should be important.展开更多
The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farm...The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farms during one year. Basis of the method for MPAS assessment is the milk sample inactivation at the temperature 80-82 ℃ for 30 minutes followed by incubation in cultivation dishes at 30 -4- 1 ℃ for 3 days-mesophilic aerobic sporulates （MAS）, and at 6.5 .4- 1 ℃ for 10 days-psychrotrophic aerobic sporulates （PAS）. The total count of MPAS was within the span 2.5-340 CFU/mL （colony forming units）. Average plate count of MPAS was 59.4 CFU/mL with variation coefficient 93.1%. MPAS count found in the same dishes at incubation for mesophilic and subsequently strictly psychrophilic microorganisms （MAS ＋ SPAS） which enables to exclude overestimation of results by sporulates able to grow at both incubation temperatures was on average 56.9 CFU/mL what represents 95.8% out of the number of sums of individual dishes at two temperatures （MAS ＋ PAS）. Correlation coefficient of these two types of results r = 0.99 gives evidence of close dependence that is expressed by linear regression equation y = 0.9773x. We can consider the method using at first 30 .4- 1 ℃ and subsequently 6.5 -4-1℃ （MAS ＋ SPAS） as more correct than the method with the opposite order of cultivation temperatures because of better regression coefficient of linear dependence and higher correlation coefficient in relation to the sum of independent incubations （MAS ＋ PAS）.展开更多
Mesophilic biogas production and substrate decomposition is one of the significant limiting steps in biogas generation. The rate of generation and quality often affect the viability of biogas systems. This study asses...Mesophilic biogas production and substrate decomposition is one of the significant limiting steps in biogas generation. The rate of generation and quality often affect the viability of biogas systems. This study assessed the potential for biogas process catalysis using powdered Sorghum bicolor L., Zea mays, and Pennisetum glaucum. The kinetics and biogas generation processes were studied. Experiments were conducted in 1 m<sup>3</sup> tubular batch reactors, where batches were dosed with various organic biomolecules. Results show that the use of P. glaucum L. and S. bicolor L. reduced the biogas retention times significantly. Biogas generation commenced after the first day for digesters fed with S. bicolor L. and P. glaucum L. while one with Z. mays and control occurred on day two. The rate of biomethanation and methane content were enhanced. S. bicolor L. led to the highest methane content. Findings reveal that locally available organic biomolecules improved biogas quality and quantity.展开更多
Microbial carbon fixation is a paramount process in the ocean especially below the photic zone both in water and sedimentary ecosystems. Autotrophic microbes that fix carbon dioxide are renowned. However, the question...Microbial carbon fixation is a paramount process in the ocean especially below the photic zone both in water and sedimentary ecosystems. Autotrophic microbes that fix carbon dioxide are renowned. However, the question whether heterotrophs can also fix carbon is intriguing. Ten heterotrophically grown, identified bacterial isolates from the Sino-Pacific marine sediments were tested for autotrophic uptake potential with and without addition of electron donors. Nine of the ten isolates showed carbon uptake capacity without addition of any substrate at very low rates in the order of 10^（-8） to 10^（-4） fmol/（cell·h）. The addition of manganese and ammonium at 1 mmol/L final concentration enhanced the uptake potential. Addition of 1 mmol/L final concentrations of reduced iron（10^（-6） to10^（-5） fmol/（cell·h） and sulfide（10^（-5） fmol/（cell·h） decreased the uptake potential significantly at p〈0.1. Bacterial tolerance to formaldehyde suggested propensities of anaplerotic chemical reactions that form metabolic intermediates of C-1 metabolism pathways. The isolates displayed high metabolic flexibility. With the changes in electron donors, the isolates metabolically toggled between relatively anoxic reductive iron/sulfur cycles and the oxidative cycles of manganese/ammonium and vice-versa. This property makes these microbes successful survivors in the highly dynamic Sino-Pacific sediments.展开更多
Polyacrylamide(PAM)is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge.Furthermore,it degrades slowly and can deteriorate methane yield during anaerobic...Polyacrylamide(PAM)is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge.Furthermore,it degrades slowly and can deteriorate methane yield during anaerobic digestion(AD).The impact or fate of PAM in AD under thermophilic conditions is still unclear.This study mainly focuses on PAM degradation and enhanced methane production from PAM-added sludge during 15 days of thermophilic(55°C)AD compared to mesophilic(35°C)AD.Sludge and PAM dose from 10 to 50 g/kg TSS were used.The results showed that PAM degraded by 76%to 78%with acrylamide(AM)content of 0.2 to 3.3 mg/L in thermophilic AD.However,it degraded only 21%to 30%with AM content of 0.5 to 7.2 mg/L in mesophilic AD.The methane yield was almost 230 to 238.4 mL/g VSS on the 8th day in thermophilic AD but was 115.2 to 128.6 mL/g VSS in mesophilic AD.Mechanism investigation revealed that thermophilic AD with continuous stirring not only enhanced PAM degradation but also boosted the organics release from the sludge with added PAM and gave higher methane yield than mesophilic AD.展开更多
Introduction: This study was carried out to assess the quality of sheep meat sold to consumers in Saaba municipality. Methods: A preliminary survey consisted of assessing hygiene and sampling meat in butchers’ stores...Introduction: This study was carried out to assess the quality of sheep meat sold to consumers in Saaba municipality. Methods: A preliminary survey consisted of assessing hygiene and sampling meat in butchers’ stores. To achieve this, 100 sales outlets were surveyed for their hygiene conditions. 25 mutton meat samples were sampled in the three villages in Saaba district and analyzed using conventional microbiological techniques. The analysis consisted of determining the microbiological characteristics. Results: According to the results of this study, 100% of the butchers surveyed were men of the region. Among these men, 13% had secondary education, 46% had primary education and 41% were illiterate. Of the 100 retail outlets visited, 96% of the sellers were unaware of the hygiene rules and the dangers of microorganisms. The microbiological analysis of the samples revealed that 100% of the meat was of unsatisfactory microbiological quality. The average contamination rate by total aerobic mesophilic flora, total coliforms, Staphylococcus aureus and yeasts and molds was 8.93 × 106, 3.12 × 105, 3.69 × 106, and 6.74 × 103 CFU/g respectively. No Salmonella strain was detected in any of the samples analyzed. Conclusion: Our results pointed out the unsatisfactory safety quality of the sheep meat sold in the sheep meat and good hygiene practices.展开更多
A bench-scale expanded granular sludge bed （EGSB） reactor was applied to the treatment of palm oil mill effluent （POME）. The reactor had been operated continuously at 35℃ for 514 d, with organic loading rate （OL...A bench-scale expanded granular sludge bed （EGSB） reactor was applied to the treatment of palm oil mill effluent （POME）. The reactor had been operated continuously at 35℃ for 514 d, with organic loading rate （OLR） increased from 1.45 to 17.5 kg COD/（m^3·d）. The results showed that the EGSB reactor had good performance in terms of COD removal on the one hand, high COD removal of 91% was obtained at two days＇ of hydraulic retention time （HRT）, and the highest OLR of 17.5 kg COD/（m^3·d）. On the other hand, only 46% COD in raw POME was transformed into biogas in which the methane content was about 70% （V/V）. A 30-d intermittent experiment indicated that the maximum transformation potential of organic matter in raw POME into methane was 56%. Volatile fatty acid （VFA） accumulation was observed in the later operation stage, and this was settled by supplementing trace metal elements. On the whole, the system exhibited good stability in terms of acidity and alkalinity. Finally, the operational problems inherent in the laboratory scale experiment and the corresponding countermeasures were also discussed.展开更多
This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium a...This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of-75+53 μm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of-53+38 μm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM-EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms(polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite-chalcocite ore. Meanwhile, the speciation turns into Cu2 S-Cu S-Cu5 Fe S4-Cu2 S before turning into Cu SO4. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 m V at room temperature for high copper leaching rate.展开更多
Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-fl...Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-flow anaerobic sludge blanket bioremediation (TS-UASBB). With the TS-UASBB, 2 4 SO , COD, N and P in the effluent from the DS degraded significantly and their concentrations were kept at 0.2 g·L -1 , 2.0 g·L -1 , 1.0 g·L -1 and 15 mg·L -1 , respectively, in 13 batch processes for water-recycled ethanol fermentation. With the effluent used directly as dilution water, no heat-resistant bacteria were found alive. The thirteen-batch ethanol production individually achieved 10% after 48 h fermentation. The starch utilization ratio and total sugar consumption were 90% and 99.5%, respectively. The novel water-recycled bioethanol production process with ethanol fermentation and TS-UASBB has a considerable potential in other starchy and cellulosic ethanol production.展开更多
The occurrence frequencies of the dinucleotides of genes of three thermophilic and three mesophilic species from both archaea and eubacteria were investigated in this study. The genes encoding water soluble proteins w...The occurrence frequencies of the dinucleotides of genes of three thermophilic and three mesophilic species from both archaea and eubacteria were investigated in this study. The genes encoding water soluble proteins were rich in the dinucleotides of purine dimers, whereas the genes encoding membrane proteins were rich in pyrimidine dimers. The dinucleotides of purine dimers are the counterparts of pyrimidine dimers in a double-stranded DNA. The purine/pyrimidine dimers were favored in the thermophiles but not in the mesophiles, based on comparisons of observed and expected frequencies. This finding is in agreement with our previous study which showed that purine/pyrimidine dimers are positive factors that increase the thermal stability of DNA. The dinucleotides AA, AG, and GA are components of the codons of charged residues of Glu, Asp, Lys, and Arg, and the dinucleotides TT, CT, and TC are components of the codons of hydrophobic residues of Leu, Ile, and Phe. This is consistent with the suitabilities of the different amino acid residues for water soluble and membrane proteins. Our analysis provides a picture of how thermophilic species produce water soluble and membrane proteins with distinctive characters: the genes encoding water soluble proteins use DNA sequences rich in purine dimers, and the genes encoding membrane proteins use DNA sequences rich in pyrimidine dimers on the opposite strand.展开更多
A kinetic study of biogas production from Urban Solid Waste (USW) generated in Dar es Salaam city (Tanzania) is presented. An experimental bioreactor simulating mesophilic conditions of most USW landfills was develope...A kinetic study of biogas production from Urban Solid Waste (USW) generated in Dar es Salaam city (Tanzania) is presented. An experimental bioreactor simulating mesophilic conditions of most USW landfills was developed. The goal of the study was to generate the kinetic order of reaction with respect to biodegradable organic waste and use it to model biogas production from food residues mixed with fruit waste. Anaerobic biodegradation was employed under temperature range of 28℃ - 38℃. The main controls were leachate recirculation and pH adjustments to minimize acid inhibitory effects and accelerate waste biodegradation. The experimental setup comprised of three sets of bioreactors. A biodegradation rate law in differential form was proposed and the numerical values of kinetic order and rate constant were determined using initial rate method as 0.994 and 0.3093 mol0.006·day-1, respectively. Results obtained were consistent with that found in literature and model predictions were in reasonable agreement with experimental data.展开更多
The copper recovery from low-grade copper sulfide ore was investigated using microbial leaching. Several parameters substantially affect the bioleaching of copper; among them, pulp density and nutrient media were sele...The copper recovery from low-grade copper sulfide ore was investigated using microbial leaching. Several parameters substantially affect the bioleaching of copper; among them, pulp density and nutrient media were selected for investigation. The optimum conditions for copper recovery were a pulp density of 5 g/mL, a mixed-mineral salt medium of Acidithiobacillus thiooxidans(70vol%) and Acidithiobacillus ferrooxidans(30vol%), and 10vol% of inoculum. Under these conditions, the maximum bioleaching capacity of the medium for copper recovery was determined to be approximately 99%. The effect of pulp density on the kinetics of the bioleaching process was surveyed using both da Silva's method and constrained multilinear regression analysis. The kinetics of copper dissolution followed the shrinking core model, and the process was diffusion controlled at a pulp density of 5 g/mL. Nevertheless, at higher pulp densities, the process was controlled by chemical reaction.展开更多
The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture compos...The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture composed of Bifidobacterium,Lactobacillus,Lactococcus,Streptococcus,Bacillus,Rhodopseudomonas,and Saccharomyces.The four processes were carried out in a shake flask with no pH control,an aerobic bioreactor without mixing with no pH control,and a stirred-tank reactor （STR） with aeration with and without pH control,respectively.All experiments were started with an initial pH 8.0.The highest efficiency of biodegradation was achieved through the processes conducted in the STR,where betaine （an organic pollutant occurring in beet molasses in very large quantities） was completely degraded by the microorganisms.The process with no pH control carried out in the STR produced the highest reduction in the following pollution measures：organic matter expressed as chemical oxygen demand determined by the dichromatic method ＋ theoretical COD of betaine （COD sum,85.5%）,total organic carbon （TOC,78.8%） and five-day biological oxygen demand （BOD 5,98.6%）.The process conditions applied in the shake flask experiments,as well as those used in the aerobic bioreactor without mixing,failed to provide complete betaine assimilation.As a consequence,reduction in COD sum,TOC and BOD 5 was approximately half that obtained with STR.展开更多
Swine wastewater (SW) and olive mill wastewater (OMW) are two problematic wastes that have become major causes of health and environmental concerns. The main objective of the current work was to evaluate the efficienc...Swine wastewater (SW) and olive mill wastewater (OMW) are two problematic wastes that have become major causes of health and environmental concerns. The main objective of the current work was to evaluate the efficiency of the co-digestion strategy for treatment of SW and OMW mixtures. Mesophilic batch reac-tors fed with mixtures of SW and OMW showed that the two adapted sludges Gadot and Prigat exhibited the best COD removal capacity and biogas production;therefore both were selected to seed up-flow anaerobic sludge blanket (UASB) continuous reactors. During 170 days of operation, both sludges Gadot and Prigat showed high biodegradation potential. The highest COD removal of 85-95% and biogas production of 0.55 L?g-1 COD were obtained at a mixture consisting of 33% OMW and 67% SW. Under these conditions, an organic load of 28,000 mg?L-1 COD was reduced to 1,500-3,500 mg?L-1. These results strongly suggest that co-digestion technology using UASB reactors is a highly reliable and promising technology for wastewater treatment and biogas production.展开更多
文摘Composting as a solution to the increasing generation of municipal solid waste (MSW), also contribute to GHGs emission when not controlled and could lack some basic nutrients, especially nitrogen. This study assessed the split-additions of nitrogen-rich substrate to composting materials and their effect on GHGs emissions as well as the quality of the composts. Nitrogen-rich substrates formulated from pig and goat manure were co-composted with MSW for a 12-weeks period by split adding at mesophilic (˚C) and thermophilic (>50˚C) stages in five different treatments. Representative samples from the compost were taken from each treatment for physicochemical, heavy metals and bacteriological analysis. In-situ CH<sub>4</sub>, CO<sub>2</sub>, N<sub>2</sub>O gas emissions were also analyzed weekly during composting. It was observed that all the treatments showed significant organic matter decomposition, reaching thermophilic temperatures in the first week of composting. The absence affects the suitable agronomic properties. All nitrogen-rich substrate applied at thermophilic stage (Treatment two) recorded the highest N, P and K concentrations of 1.34%, 0.97% and 2.45%, respectively with highest nitrogen retention. In terms of GHG emissions, CO<sub>2</sub> was highest at the thermophilic stage when N-rich substrate was added in all treatment, while CH<sub>4</sub> was highest in the mesophilic stage with N-rich substrate addition. N<sub>2</sub>O showed no specific trend in the treatments. Split addition of the N-rich substrate for co-composting of MSW produced compost which is stable, has less nutrient loss and low GHG emissions. Split addition of a nitrogen-rich substrate could be an option for increasing the fertilizer value of MSW compost.
基金supported by the Ministry of Science and Technology(2020YFA0907700)National Natural Science Foundation of China(31770078,32270051)Shanghai Pilot Program for Basic Research-Shanghai Jiao Tong University(21TQ1400204).
文摘Mesophilic Argonautes(Agos)from microbial resources have received significant attention due to their potential applications in genome editing and molecular diagnostics.This study characterizes a novel Ago from Pseudobutyrivi-brio ruminis(PrAgo),which can cleave single-stranded DNA using guide DNA(gDNA).PrAgo,functioning as a multi-turnover enzyme,effectively cleaves DNA using 5′-phosphate gDNA,14-30 nucleotides in length,in the presence of both Mn2+and Mg2+ions.PrAgo demonstrates DNA cleavage activity over a broad pH range(pH 4-12),with optimal activity at pH 11.As a mesophilic enzyme,PrAgo cleaves efficiently DNA at temperatures ranging from 25 to 65°C,particularly at 65°C.PrAgo does not show strong preferences for the 5′-nucleotide in gDNA.It shows high tolerance for single-base mismatches,except at positions 13 and 15 of gDNA.Continuous double-nucleotide mismatches at positions 10-16 of gDNA significantly reduce cleavage activity.Furthermore,PrAgo mediates DNA-guided DNA cleavage of AT-rich double stranded DNA at 65°C.Additionally,molecular dynamic simulations suggest that interactions between the PAZ domain and different nucleic acids strongly influence cleavage efficiency.These findings expand our understanding of Protokaryotic Agos and their potential applications in biotechnology.
基金Project supported by the Grant-in-Aid for Science Research of Japan Society for the Promotion of Science (JSPS), Japan.
文摘Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide （BAA）-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.
基金supported by the National Iranian Copper Industry Co. and Geological Survey of Iran
文摘The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recoveries in a bioleaching process was investigated.Three main bioleaching parameters,namely pH,solid concentration and inoculum percent,were changed during the bioleaching tests based on CCD.The ranges of the bioleaching process variables used in the design were as follows：pH1.46-2.14,solid concentration 0.95%-11.05%,and inoculum percent 1.59%-18.41%.A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix.Empirical model equations were developed according to the copper,molybdenum and rhenium recoveries obtained with these three parameters.Model equations of responses at the base of parameters were achieved by using statistical software.The model equations were then individually optimized by using quadratic programming to maximize copper,molybdenum and rhenium recoveries individually within the experimental range.The optimum conditions for copper recovery were pH 1.68,solid concentration 0.95% and the inoculum 18.41%（v/v）,while molybdenum and rhenium recoveries were 2.18% and 24.41%,respectively.The predicted values for copper,molybdenum and rhenium recoveries were found to be in good agreement with the experimental values.Also jarosite formation during bioleaching tests was also investigated.
基金supported by the National Iranian Copper Industry Co.
文摘Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate.Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor.The shake flask tests were performed with different inoculum size,solids density,pH.and temperature in order to identify optimum conditions.The highest amount of copper elimination,75%was obtained with extreme thermophilic microorganisms(at 12%inoculation,10%solids,65℃and a pH of 1.5).The highest copper elimination by mesophilic microorganisms was 55%(at 12%inoculation,5%solids,30℃at pH 2).The optimum conditions in shake flask tests were applied to 7 days batch tests in a50-L bioreactor.Extreme thermophilic experiment gave the best copper elimination of 60%(at 12%inoculation,10%solids,65℃and pH 1.5).Mesophilic test removed 50%of the copper(at 12%inoculation,10%solids,35℃at pH 2).
文摘Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flow rate of 3.12 L·m-2·h-1 and pH 1.5 passed through each column continuously for 90 d. In the first and the second column, bioleaching was performed without agglomeration of the ore and on the agglomerated ore, respectively. 28wt% of the copper was extracted in the first column after 40 d, while this figure was 38wt% in the second column. After 90 d, however, the overall extractions were almost the same for both of them. Bioleaching with mesophilic bacteria was performed in the third column without agglomeration of the ore and in the fourth column on the agglomerated ore. After 40 d, copper extractions in the third and the fourth columns were 62wt% and 70wt%, respectively. Copper extractions were 75wt% for both the columns after 90 d. For the last column, bioleaching was performed with moderate thermophilic bacteria and agglomerated ore. Copper extractions were 80wt% and 85wt% after 40 and 90 d, respectively. It was concluded that crushing and agglomeration of the ore using bacteria could enhance the copper extraction considerably.
基金the National Basic Research Program of China (No. 2004CB619206).
文摘In this work, low-grade copper sulfide mine has been treated by the bioleaching process using native cultures of Acidithiobacillus ferrooxidans. The bioleaching experiments were carded out in shake flasks at pH 2.0, 180 r.min^-1 and 30℃ for mesophilic bacteria The conductivity of copper bioleaching liquid was determined by the electric conductivity method at temperatures ranging from 298 K to 313 K. The ionic activity coefficients were estimated using Debye-Hucker and Osager-Falkenlagen equations. Meanwhile, the effects of temperature and concentrtion on the mean ionic activity coefficients were discussed. The relative partial molar free energies, enthalpies and entropies of copper teaching solution at above experimental temperatures were calculated. The behaviors of change of relative partial molar quantities were discussed on the basis of electrolytic solution theory. Simultaneously, the thermodynamic characters of bioleaching solution with and without mesophilic bacteria were compared. The existence of mesophilic bacteria changed the Fe^3＋/Fe^2＋ ratio, which resulted in the difference of ionic interaction. The experimental data show that the determination of the thermodynamic properties during the bioleaching processes should be important.
文摘The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farms during one year. Basis of the method for MPAS assessment is the milk sample inactivation at the temperature 80-82 ℃ for 30 minutes followed by incubation in cultivation dishes at 30 -4- 1 ℃ for 3 days-mesophilic aerobic sporulates （MAS）, and at 6.5 .4- 1 ℃ for 10 days-psychrotrophic aerobic sporulates （PAS）. The total count of MPAS was within the span 2.5-340 CFU/mL （colony forming units）. Average plate count of MPAS was 59.4 CFU/mL with variation coefficient 93.1%. MPAS count found in the same dishes at incubation for mesophilic and subsequently strictly psychrophilic microorganisms （MAS ＋ SPAS） which enables to exclude overestimation of results by sporulates able to grow at both incubation temperatures was on average 56.9 CFU/mL what represents 95.8% out of the number of sums of individual dishes at two temperatures （MAS ＋ PAS）. Correlation coefficient of these two types of results r = 0.99 gives evidence of close dependence that is expressed by linear regression equation y = 0.9773x. We can consider the method using at first 30 .4- 1 ℃ and subsequently 6.5 -4-1℃ （MAS ＋ SPAS） as more correct than the method with the opposite order of cultivation temperatures because of better regression coefficient of linear dependence and higher correlation coefficient in relation to the sum of independent incubations （MAS ＋ PAS）.
文摘Mesophilic biogas production and substrate decomposition is one of the significant limiting steps in biogas generation. The rate of generation and quality often affect the viability of biogas systems. This study assessed the potential for biogas process catalysis using powdered Sorghum bicolor L., Zea mays, and Pennisetum glaucum. The kinetics and biogas generation processes were studied. Experiments were conducted in 1 m<sup>3</sup> tubular batch reactors, where batches were dosed with various organic biomolecules. Results show that the use of P. glaucum L. and S. bicolor L. reduced the biogas retention times significantly. Biogas generation commenced after the first day for digesters fed with S. bicolor L. and P. glaucum L. while one with Z. mays and control occurred on day two. The rate of biomethanation and methane content were enhanced. S. bicolor L. led to the highest methane content. Findings reveal that locally available organic biomolecules improved biogas quality and quantity.
基金The National Natural Science Foundation of China under contract Nos 41406062 and 41250110530the Chinese Academy of Science Fellowship for Young Foreign Scientists under contract No.2012Y1ZA0005
文摘Microbial carbon fixation is a paramount process in the ocean especially below the photic zone both in water and sedimentary ecosystems. Autotrophic microbes that fix carbon dioxide are renowned. However, the question whether heterotrophs can also fix carbon is intriguing. Ten heterotrophically grown, identified bacterial isolates from the Sino-Pacific marine sediments were tested for autotrophic uptake potential with and without addition of electron donors. Nine of the ten isolates showed carbon uptake capacity without addition of any substrate at very low rates in the order of 10^（-8） to 10^（-4） fmol/（cell·h）. The addition of manganese and ammonium at 1 mmol/L final concentration enhanced the uptake potential. Addition of 1 mmol/L final concentrations of reduced iron（10^（-6） to10^（-5） fmol/（cell·h） and sulfide（10^（-5） fmol/（cell·h） decreased the uptake potential significantly at p〈0.1. Bacterial tolerance to formaldehyde suggested propensities of anaplerotic chemical reactions that form metabolic intermediates of C-1 metabolism pathways. The isolates displayed high metabolic flexibility. With the changes in electron donors, the isolates metabolically toggled between relatively anoxic reductive iron/sulfur cycles and the oxidative cycles of manganese/ammonium and vice-versa. This property makes these microbes successful survivors in the highly dynamic Sino-Pacific sediments.
基金The present work was supported by Key Program of the National Natural Science Foundation China(No.41773082,41573065)the National Key Research project on Water Environment Pollution Control in China(No.2017ZX07202002).
文摘Polyacrylamide(PAM)is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge.Furthermore,it degrades slowly and can deteriorate methane yield during anaerobic digestion(AD).The impact or fate of PAM in AD under thermophilic conditions is still unclear.This study mainly focuses on PAM degradation and enhanced methane production from PAM-added sludge during 15 days of thermophilic(55°C)AD compared to mesophilic(35°C)AD.Sludge and PAM dose from 10 to 50 g/kg TSS were used.The results showed that PAM degraded by 76%to 78%with acrylamide(AM)content of 0.2 to 3.3 mg/L in thermophilic AD.However,it degraded only 21%to 30%with AM content of 0.5 to 7.2 mg/L in mesophilic AD.The methane yield was almost 230 to 238.4 mL/g VSS on the 8th day in thermophilic AD but was 115.2 to 128.6 mL/g VSS in mesophilic AD.Mechanism investigation revealed that thermophilic AD with continuous stirring not only enhanced PAM degradation but also boosted the organics release from the sludge with added PAM and gave higher methane yield than mesophilic AD.
文摘Introduction: This study was carried out to assess the quality of sheep meat sold to consumers in Saaba municipality. Methods: A preliminary survey consisted of assessing hygiene and sampling meat in butchers’ stores. To achieve this, 100 sales outlets were surveyed for their hygiene conditions. 25 mutton meat samples were sampled in the three villages in Saaba district and analyzed using conventional microbiological techniques. The analysis consisted of determining the microbiological characteristics. Results: According to the results of this study, 100% of the butchers surveyed were men of the region. Among these men, 13% had secondary education, 46% had primary education and 41% were illiterate. Of the 100 retail outlets visited, 96% of the sellers were unaware of the hygiene rules and the dangers of microorganisms. The microbiological analysis of the samples revealed that 100% of the meat was of unsatisfactory microbiological quality. The average contamination rate by total aerobic mesophilic flora, total coliforms, Staphylococcus aureus and yeasts and molds was 8.93 × 106, 3.12 × 105, 3.69 × 106, and 6.74 × 103 CFU/g respectively. No Salmonella strain was detected in any of the samples analyzed. Conclusion: Our results pointed out the unsatisfactory safety quality of the sheep meat sold in the sheep meat and good hygiene practices.
文摘A bench-scale expanded granular sludge bed （EGSB） reactor was applied to the treatment of palm oil mill effluent （POME）. The reactor had been operated continuously at 35℃ for 514 d, with organic loading rate （OLR） increased from 1.45 to 17.5 kg COD/（m^3·d）. The results showed that the EGSB reactor had good performance in terms of COD removal on the one hand, high COD removal of 91% was obtained at two days＇ of hydraulic retention time （HRT）, and the highest OLR of 17.5 kg COD/（m^3·d）. On the other hand, only 46% COD in raw POME was transformed into biogas in which the methane content was about 70% （V/V）. A 30-d intermittent experiment indicated that the maximum transformation potential of organic matter in raw POME into methane was 56%. Volatile fatty acid （VFA） accumulation was observed in the later operation stage, and this was settled by supplementing trace metal elements. On the whole, the system exhibited good stability in terms of acidity and alkalinity. Finally, the operational problems inherent in the laboratory scale experiment and the corresponding countermeasures were also discussed.
文摘This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of-75+53 μm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of-53+38 μm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM-EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms(polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite-chalcocite ore. Meanwhile, the speciation turns into Cu2 S-Cu S-Cu5 Fe S4-Cu2 S before turning into Cu SO4. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 m V at room temperature for high copper leaching rate.
基金Supported by the National High Technology Research and Development Program of China （2008AA10Z338） the National Natural Science Foundation of China （20906041）
文摘Considering limited success in target-hitting discharge from alcohol industry, our attention was directed toward a recycling use of distillery spentwash (DS) in cassava bioethanol production by using a two-stage up-flow anaerobic sludge blanket bioremediation (TS-UASBB). With the TS-UASBB, 2 4 SO , COD, N and P in the effluent from the DS degraded significantly and their concentrations were kept at 0.2 g·L -1 , 2.0 g·L -1 , 1.0 g·L -1 and 15 mg·L -1 , respectively, in 13 batch processes for water-recycled ethanol fermentation. With the effluent used directly as dilution water, no heat-resistant bacteria were found alive. The thirteen-batch ethanol production individually achieved 10% after 48 h fermentation. The starch utilization ratio and total sugar consumption were 90% and 99.5%, respectively. The novel water-recycled bioethanol production process with ethanol fermentation and TS-UASBB has a considerable potential in other starchy and cellulosic ethanol production.
文摘The occurrence frequencies of the dinucleotides of genes of three thermophilic and three mesophilic species from both archaea and eubacteria were investigated in this study. The genes encoding water soluble proteins were rich in the dinucleotides of purine dimers, whereas the genes encoding membrane proteins were rich in pyrimidine dimers. The dinucleotides of purine dimers are the counterparts of pyrimidine dimers in a double-stranded DNA. The purine/pyrimidine dimers were favored in the thermophiles but not in the mesophiles, based on comparisons of observed and expected frequencies. This finding is in agreement with our previous study which showed that purine/pyrimidine dimers are positive factors that increase the thermal stability of DNA. The dinucleotides AA, AG, and GA are components of the codons of charged residues of Glu, Asp, Lys, and Arg, and the dinucleotides TT, CT, and TC are components of the codons of hydrophobic residues of Leu, Ile, and Phe. This is consistent with the suitabilities of the different amino acid residues for water soluble and membrane proteins. Our analysis provides a picture of how thermophilic species produce water soluble and membrane proteins with distinctive characters: the genes encoding water soluble proteins use DNA sequences rich in purine dimers, and the genes encoding membrane proteins use DNA sequences rich in pyrimidine dimers on the opposite strand.
文摘A kinetic study of biogas production from Urban Solid Waste (USW) generated in Dar es Salaam city (Tanzania) is presented. An experimental bioreactor simulating mesophilic conditions of most USW landfills was developed. The goal of the study was to generate the kinetic order of reaction with respect to biodegradable organic waste and use it to model biogas production from food residues mixed with fruit waste. Anaerobic biodegradation was employed under temperature range of 28℃ - 38℃. The main controls were leachate recirculation and pH adjustments to minimize acid inhibitory effects and accelerate waste biodegradation. The experimental setup comprised of three sets of bioreactors. A biodegradation rate law in differential form was proposed and the numerical values of kinetic order and rate constant were determined using initial rate method as 0.994 and 0.3093 mol0.006·day-1, respectively. Results obtained were consistent with that found in literature and model predictions were in reasonable agreement with experimental data.
基金financially supported by the National Iranian Copper Industry Co.
文摘The copper recovery from low-grade copper sulfide ore was investigated using microbial leaching. Several parameters substantially affect the bioleaching of copper; among them, pulp density and nutrient media were selected for investigation. The optimum conditions for copper recovery were a pulp density of 5 g/mL, a mixed-mineral salt medium of Acidithiobacillus thiooxidans(70vol%) and Acidithiobacillus ferrooxidans(30vol%), and 10vol% of inoculum. Under these conditions, the maximum bioleaching capacity of the medium for copper recovery was determined to be approximately 99%. The effect of pulp density on the kinetics of the bioleaching process was surveyed using both da Silva's method and constrained multilinear regression analysis. The kinetics of copper dissolution followed the shrinking core model, and the process was diffusion controlled at a pulp density of 5 g/mL. Nevertheless, at higher pulp densities, the process was controlled by chemical reaction.
文摘The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture composed of Bifidobacterium,Lactobacillus,Lactococcus,Streptococcus,Bacillus,Rhodopseudomonas,and Saccharomyces.The four processes were carried out in a shake flask with no pH control,an aerobic bioreactor without mixing with no pH control,and a stirred-tank reactor （STR） with aeration with and without pH control,respectively.All experiments were started with an initial pH 8.0.The highest efficiency of biodegradation was achieved through the processes conducted in the STR,where betaine （an organic pollutant occurring in beet molasses in very large quantities） was completely degraded by the microorganisms.The process with no pH control carried out in the STR produced the highest reduction in the following pollution measures：organic matter expressed as chemical oxygen demand determined by the dichromatic method ＋ theoretical COD of betaine （COD sum,85.5%）,total organic carbon （TOC,78.8%） and five-day biological oxygen demand （BOD 5,98.6%）.The process conditions applied in the shake flask experiments,as well as those used in the aerobic bioreactor without mixing,failed to provide complete betaine assimilation.As a consequence,reduction in COD sum,TOC and BOD 5 was approximately half that obtained with STR.
文摘Swine wastewater (SW) and olive mill wastewater (OMW) are two problematic wastes that have become major causes of health and environmental concerns. The main objective of the current work was to evaluate the efficiency of the co-digestion strategy for treatment of SW and OMW mixtures. Mesophilic batch reac-tors fed with mixtures of SW and OMW showed that the two adapted sludges Gadot and Prigat exhibited the best COD removal capacity and biogas production;therefore both were selected to seed up-flow anaerobic sludge blanket (UASB) continuous reactors. During 170 days of operation, both sludges Gadot and Prigat showed high biodegradation potential. The highest COD removal of 85-95% and biogas production of 0.55 L?g-1 COD were obtained at a mixture consisting of 33% OMW and 67% SW. Under these conditions, an organic load of 28,000 mg?L-1 COD was reduced to 1,500-3,500 mg?L-1. These results strongly suggest that co-digestion technology using UASB reactors is a highly reliable and promising technology for wastewater treatment and biogas production.
