Gas biofuels from solid substrate hydrogenogenic–methanogenic fermentation of the organic fraction of municipal solid waste

The objective of this work was to evaluate the performance of a two-stage hydrogenogenic–methanogenic (H–M) semi-continuous process in terms of mass retention time (MRT) for hydrogenogenic stage (H-stage), feed source for methanogenic stage (M-stage) and thermal regime (35 and 55 °C) for both stages. The substrate was a model organic fraction of municipal solid wastes (OFMSW) at 35% total solids.In H-stage, mesophilic temperature had a positive significant effect on higher hydrogen productivities and lower amounts of hydrogen sinks compared to thermophilic operation. Calculations based on mass balances and biochemical stoichiometry confirmed that acid fermentation deviation was linked to low biohydrogen yields. The M-stage performance was influenced by both the temperature and feed source. Bioreactors in thermophilic regime performed better than mesophilic ones. Maximum methane productivity was 341 NmL CH₄/(kg_wmr d) that corresponded to the thermophilic bioreactor fed with fermented solids from H stage at 14 d MRT. The two-stage process showed higher gross energetic potential when compared to an only methanogenic process operated at equivalent MRT (control); this was due to a higher methane productivity in the M-stage of the series process. The main contribution of H-stage seemed to be associated to hydrolysis of the complex substrate thus generating metabolites for the M-stage rather than the hydrogen production itself.     

Quantitative recovery of fungal biomass grown on solid κ- carrageenan media

The use of a dissolvable solid matrix, -carrageenan, to quantify biomass grown on solid media was studied. A firm gel was obtained with 2% (w/v) -carrageenan and 20 mM K+ which could be easily dissolved in demineralized water. Direct quantification of Coniothyrium minitans biomass grown on this medium was feasible. No effects of the dissolution on the amount of biomass recovered were detected.     

Production kinetics of β-carotene from Planococcus sp. TRC1 with concomitant bioconversion of industrial solid waste into crystalline cellulose rich biomass

Cost effective bioprocessing of nutraceuticals in present global scenario is a matter of concern. This study explored Paper mill sludge (PMS) and sugarcane bagasse (SCB) as inexpensive substrate for Planococcus sp. TRC1 mediated valuable β-carotene production and residual treated biomass as value added crystalline cellulose source simultaneously. Both biomass supported significant bacterial growth reaching highest yield 38.54 ± 1.4 mg/g on PMS (36 h) and 47.13 ± 1.9 mg/g (48 h) on SCB in solid state fermentation. Luedeking-Piret model revealed growth associated production with α and much lower β values of 5.18 and 0.24 for PMS and 4.5 and 0.165 for SCB. Cost analysis exhibited decrementation of pigment cost/mg by 84 % compared to synthetic media. Optimum production conditions were 30 °C temperature, pH 7, 10 % inoculum and initial moisture content 80 % (PMS) and 85 % (SCB). TLC (R_f = 0.9), HPLC (RT = 7.646) and lambda max (465 nm) confirmed pigment’s β-carotene nature with significant antioxidant and antimicrobial activity. It showed stability at varied temperature, pH and light conditions along with negligible phytotoxicity on Vigna radiata. Planococcus sp. TRC1 delignified PMS (41 %) and SCB (38 %) and FT-IR, FESEM and XRD suggested crystalline nature of residual cellulose rich fraction shedding light on a biorefinery approach for valorization of industrial solid wastes.     

Theoretical study on interactions of β-cyclodextrin with helicobacter pylori eradicating agent (TG44)

The inclusion complex of β-cyclodextrin (β-CD) and 4-methylbenzyl-4′-[trans-4- (guanidinomethyl)cylohexylcarbonyloxy]-biphenyl-4-carboxlylate monohydrochloride (TG44) had been investigated by using densify functional theory (DFT) and PM3 semiempirical method. The results indicate that the β-CD includes predominantly the biphenyl moiety of TG44, and the inclusion complex formed by TG44 entering into the cavity of β-CD from its narrow side (the primary hydroxyl group side) is more stable than that formed by TG44 entering into the cavity of β-CD from its wide side (the secondary hydroxyl group side). The negative enthalpy changes calculated from the statistical thermodynamic calculations at 1 atm and 298.15 K suggest that the inclusion complexes are favored enthalpy-driven processes. The molecular modeling results are in good agreement with the experiment for 2D ¹H–¹³C H HETCOR spectroscopic and H-NMR spectroscopic observations.     

Integrated anaerobic–aerobic systems for solid waste treatment

ACEA is a modern Italian multi-utility company, which currently provides services for Municipalities, private companies and citizens. The Waste Treatment facilities of ACEA Pinerolese Industriale S.p.A. have been developed during years 2001?C2003. The entire process is based on the connection of four different treatment plants (anaerobic digestion, composting plant, wastewater treatment plant and a landfill), where both anaerobic and aerobic digestion take place. The efficiency of the system is aligned to literature data for best efficiency as we can see from the 0,534?m³/KgVS_fed of the specific biogas production and from the substrate removal effectiveness reaching 69?% in 4?years time data. Moreover, the amount of energy consumed by the anaerobic digestion (AD) treatment is less than the 27?% of the energy produced by the AD system, which is a remarkable gain in efficiency.     

GPU-accelerated replica exchange molecular simulation on solid–liquid phase transition study of Lennard-Jones fluids

Determining the solid–liquid phase transition point by conventional molecular dynamics (MD) simulations is difficult because of the tendency of the system to get trapped in local minimum energy states at low temperatures and hysteresis during cooling and heating cycles. The replica exchange method, used in performing many MD simulations of the system at different temperature conditions simultaneously and performs exchanges of these temperatures at certain intervals, has been introduced as a tool to overcome this local-minimum problem. However, around the phase transition temperature, a greater number of different temperatures are required to adequately find the phase transition point. In addition, the number of different temperature values increases when treating larger systems resulting in huge computation times. We propose a computational acceleration of the replica exchange MD simulation on graphics processing units (GPUs) in studying first-order solid–liquid phase transitions of Lennard-Jones (LJ) fluids. The phase transition temperature for a 108-atom LJ fluid has been calculated to validate our new code. The result corresponds with that of a previous study using multicanonical ensemble. The computational speed is measured for various GPU-cluster sizes. A peak performance of 196.3 GFlops with one GPU and 8.13 TFlops with 64 GPUs is achieved.     

Production and characterization of β-glucosidase from Aspergillus niger fermentation: Application for organic fraction of municipal solid waste hydrolysis and methane enhancement

The anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) is currently an attractive treatment process with energy production in the form of biogas. Hydrolysis is the rate-limiting step for the anaerobic digestion of solid wastes. Thus, in the present study fungal enzymatic pretreatment of OFMSW was applied to enhance biogas production. Two enzyme cocktails rich on β-glucosidase were produced from submerged fermentation of Aspergillus niger on basal medium using OFMSW as carbon source and urea (Urea cocktail) and Ulva rigida as nitrogen source (Ulva cocktail). Ulva cocktail displayed an important effect on OFMSW solubilization. Therefore, an increase of reducing sugar concentration about 60% was obtained which was in correlation with chemical oxygen demand (COD) increase. The performance of enzymatic pretreatment on anaerobic digestion of OFMSW was studied by conducting biochemical methane potential tests. Results showed that the enzymatic pretreatment improved methane yield of OFMSW even at high solid concentration. High methane yield about 500 ml/g total volatile solid was obtained, which corresponds up to 68% enhancement over the control.     

Molecular simulation of solid–solid phase transitions

Applications of dl_poly to solid–solid phase transitions are reviewed, with particular attention to how details of the mechanisms of the transitions may be extracted from molecular dynamics simulations. Two examples in molecular crystals are discussed: the order–disorder transition of p-terphenyl initiated at around 200 K by the unlocking of ring flipping; and the rotator phases of n-alkanes with around 20 carbon atoms per chain, showing distinct molecular mechanisms in the dynamics just below the melting points of odd and even chains. Covalent-ionic materials are represented by an application to an aluminophophate molecular sieve, AlPO₄-5.     

Toxicological screening of chemical emissions from municipal solid waste landfills. application of a predictive framework to a state‐of‐the‐art facility

A screening‐level risk assessment was used to identify chemicals of potential health concern emitted during the normal operation of an hypothetical state‐of‐the‐art municipal solid waste landfill. Data on the amount of contaminants (carcinogens, non‐carcinogenic systemic toxicants, odorous compounds, and particulate‐bound metals) were obtained from existing facilities and used to estimate ground‐level air concentrations of airborne chemicals at the point of maximum impact (property line) and at year 20 (year of maximum emissions from the landfill). Concentrations of leachate components present in the corresponding underlying aquifer were also estimated. Intakes of chemicals experienced by a series of human receptors were then computed using either single‐media or multi‐media algorithms. Carcinogens of concern were selected as those contributing to a lifetime excess cancer risk (LECR) greater than 10^‐6; for non‐carcinogenic systemic toxicants and odorous volatiles an Exposure Ratio (ER=intake or concentration/RfD, RfC, odor threshold) greater than 0.1 was used as cut‐off. The results obtained identified a final set of air emission components (n = 25) constituted mainly of carcinogenic and odorous substances whereas 2 leachate components were retained. Additional analysis using more refined risk‐based approaches are necessary to verify the relevance of these projections.     

Probing RNA–antibiotic interactions: a FTIR study

The crystal structure determination of antibiotic binding sites on the 30S ribosomal subunit and the increasing demand for developing RNA-based drugs has prompted us to study the direct binding of spectinomycin, vancomycin and bleomycin with yeast total RNA using Fourier transform infrared (FTIR) spectroscopy. We report that the OH of spectinomycin and the peptide group of vancomycin can bind to the bases of RNA, which might depend on Mg²⁺ concentration. Bleomycin on the other hand does not show such a drastic effect on yeast total RNA. This study might help in developing innovative strategies utilizing RNA molecules to perform a variety of essential biological functions.     

Isolation and screening of low-density polyethylene (LDPE) bags degrading bacteria from Addis Ababa municipal solid waste disposal site “Koshe”

Purpose

The present study aimed to explore the binding ability of acyl-CoA binding protein 2 to fatty acid acyl-CoA esters and its effect on Monascus pigment production in M. ruber CICC41233.

Methods

The Mracbp2 gene from M. ruber CICC41233 was cloned with a total DNA and cDNA as the templates through the polymerase chain reaction. The cDNA of the Mracbp2 gene fragment was ligated to expression vector pGEX-6P-1 to construct pGEX-MrACBP2, which was expressed in Escherichia coli BL21 to obtain the fusion protein GST-MrACBP2 and then measure the binding ability of fatty acid acyl-CoA esters. Additionally, the DNA of the Mracbp2 gene fragment was ligated to expression vector pNeo0380 to construct pNeo0380-MrACBP2, which was homologously over-expressed in M. ruber CICC41233 to evaluate Monascus pigment production and fatty acid.

Results

The cloned Mracbp2 gene of the DNA and cDNA sequence was 1525 bp and 1329 bp in length, respectively. The microscale thermophoresis binding assay revealed that the purified GST-MrACBP2 had the highest affinity for palmitoyl-CoA (Kd =70.57 nM). Further, the Mracbp2 gene was homologously overexpressed in M. ruber CICC41233, and a positive transformant M. ruber ACBP-E was isolated. In the Monascus pigments fermentation, the expression level of the Mracbp2 gene was increased by 1.74-fold after 2 days and 2.38-fold after 6 days. The palmitic acid content and biomass in M. ruber ACBP2-E were significantly lower than that in M. ruber CICC41233 on 2 days and 6 days. However, compared with M. ruber CICC41233, the yields of total pigment, ethanol-soluble pigment, and water-soluble pigment in M. ruber ACBP2-E increased by 63.61%, 71.61%, and 29.70%, respectively.

Conclusions

The purified fusion protein GST-MrACBP2 exhibited the highest affinity for palmitoyl-CoA. The Mracbp2 gene was overexpressed in M. ruber CICC41233, which resulted in a decrease in palmitic acid and an increase in Monascus pigments. Overall, the effect of MrACBP2 on the synthesis of fatty acid and Monascus pigment was explored. This paper explored the effect of MrACBP2 on the fatty acid synthesis and the synthesis of Monascus pigment. The results indicated the regulation of fatty acid synthesis could affect Monascus pigment synthesis, providing a novel strategy for improving the yield of Monascus pigment.

     

Production of biomass, carotenoid and other lipid metabolites by several red yeast strains cultivated on waste glycerol from biofuel production – a comparative screening study

This study was focused on a comparison of growth and production properties of seven red yeast strains of the genus Rhodotorula, Sporobolomyces and Cystofilobasidium cultivated on glycerol substrate. Production of enriched yeast biomas and specific yeast metabolites (carotenoids, ergosterol, lipids) was evaluated on medium with glucose, pure technical glycerol and/or waste glycerol from biofuel production (40 g/L) and mixture of glycerol and glucose (1:3, 1:1, 3:1; C/N ratio 57 in all cultivations). All tested strains were able to utilize glycerol as the only carbon source. Production of biomass on waste glycerol was in most strains higher than in control as well as in medium with pure technical glycerol and reached 15.97–21.76 g/L. Production of carotenoids and ergosterol was better in glucose medium than in medium with glycerol only. Nevertheless, using glycerol medium with addition of glucose, higher yields of total carotenoids, beta-carotene and ergosterol were obtained than in control. The highest yields of total pigments were reached by Sporobolomyces roseus (3.60 mg/g cell dry weight (CDW); glycerol:glucose 1:3), Sporobolomyces salmonicolor (2.85 mg/g CDW; glycerol:glucose 1:3) and Rhodotorula glutinis (2.80 mg/g CDW; glycerol:glucose 3:1) In glucose medium, most tested strains except Cystofilobasidium capitatum (22.6 %) produced neutral lipids in the range of 11–15 %. Production of triacylglycerols in all strains was in 10–30 % better in glycerol medium, in which Rhodotorula aurantiaca and Sporobolomyces shibatanus also reached intracellular triacylglycerol concentrations up to 20 % of biomass. This study has shown that oleaginous red yeasts could have great potential for converting crude glycerol to valuable lipids and carotenoids in respect of efficient bioresources utilization.     

Sequential anaerobic–aerobic degradation of munitions waste

A sequential anaerobic–aerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was studied. The results demonstrated that: (i) a complete degradation of RDX was achieved within 20 days using a consortium of bacteria from a wastewater activated sludge, (ii) RDX degradation did not occur under aerobic conditions alone, (iii) RDX-degrading bacterial strain that was isolated from the activated sludge completely degraded RDX within 2 days, and (iv) RDX- induced protein expressions were observed in the RDX-degrading bacterial strain. Based on fatty acid composition and a confirmation with a 16S rRNA analysis, the RDX-degrading bacterial strain was identified as a Bacillus pumilus—GC subgroup B.     

Life cycle assessment of composite packaging waste management—a Chinese case study on aseptic packaging

Purpose

Approximately 46,000 t/day of packaging waste was generated in China in 2010, of which, 2,500 t was composite packaging waste. Due to the lack of recycling technology and an imperfect recovery system, most of this waste is processed in sanitary landfills. An effective packaging waste management system is needed since this waste not only uses up valuable resources, but also increases environmental pollution. The purpose of this study is to estimate the environmental impact of the treatment scenarios in composite packaging waste which are commonly used in China, to determine the optimum composite packaging waste management strategy, and to design new separating and recycling technology for composite packaging, based on the life cycle assessment (LCA) results.

Methods

To identify the best treatment for composite packaging waste, the LCA software SimaPro 7.1.6 was used to assist in the analysis of the environmental impacts, coupled with the impact assessment method Eco-Indicator 99. LCA for composite packaging waste management was carried out by estimating the environmental impacts of the four scenarios most often used in China: landfill, incineration, paper recycling, and separation of polyethylene and aluminum. One ton of post-consumption Tetra Pak waste was selected as the functional unit. The data on the mass, energy fluxes, and environmental emissions were obtained from literature and site investigations.

Results and discussion

Landfill—scenario 1—was the worst waste management option. Paper recycling—scenario 3—was more environmentally friendly than incineration, scenario 2. Scenario 4, separating out polyethylene and aluminum, was established based on the LCA result, and inventory data were obtained from the demonstration project built by this research. In scenario 4, the demonstration project for the separation of polyethylene and aluminum was built based on the optimum conditions from single-factor and orthogonal experiments. Adding this flow process into the life cycle of composite packaging waste treatment decreased the environmental impacts significantly.

Conclusions

The research results can provide useful scientific information for policymakers in China to make decisions regarding composite packaging waste. Incineration could reduce more environmental impacts in the respiratory inorganics category, and separation of polyethylene and aluminum, in the fossil fuel category. If energy saving is the primary governmental goal, the separation of polyethylene and aluminum would be the better choice, while incineration would be the better choice for emission reduction.     

Can multiple harvest of aboveground biomass enhance removal of trace elements in constructed wetlands receiving municipal sewage?

Constructed wetlands for wastewater treatment in the Czech Republic are commonly planted with reed canarygrass (Phalaris arundinacea). Phalaris is a fast-growing grass which may be cut several times during the growing season. During 2005, the experiments were carried out at horizontal sub-surface flow constructed wetland B?ehov to evaluate whether multiple harvest may increase the amount of 23 trace elements removable via mowing. The plants were cut in mid-June and re-harvested in mid-August. The single harvest was carried out at the end of July during the peak standing crop of this species. The biomass of Phalaris cut once and twice during the year was nearly identical but analyses of the biomass indicated that the amount (standing stock) of trace elements varied. For 13 elements (As, Ba, Co, Cr, Cu, Fe, Ga, Hg, Mn, Ni, Pb, Sb and U) the standing stock was higher for single harvest, indicating that these trace elements are transported to the aboveground biomass later in the growing season. Standing stock found in the biomass harvested at the peak standing crop as percentage of the cumulative standing stock from two harvests was highest for Hg (385%), Pb (249%) and U (244%). On the other hand, for 10 elements (Al, Cd, Li, Mo, Rb, Se, Sn, Sr, Tl and Zn) cumulative standing stock was higher than the standing stock for one harvest, indicating high accumulation during the early growth stages. For those elements, multiple harvest could be beneficial for element removal from wastewater.     

Length–biomass equations to allow rapid assessment of semi-aquatic bug biomass in tropical streams

Length–biomass equations are relatively easy and cost-effective for deriving insect biomass. However, the exact relationship can vary between taxa and geographical regions. Semi-aquatic bugs are abundant and are indicators of freshwater quality, but there are no studies investigating the effect of habitat disturbance on their biomass, although it is useful in assessing ecological processes. We identified the best-fit length–biomass models to predict the biomass of semi-aquatic bugs (Hemiptera, Gerromorpha) collected from streams in Sabah, Malaysia. We used 259 juvenile and adult semi-aquatic bugs to compare a range of plausible length–biomass functions, and to assess whether relationships differed across the following families and body forms: (1) Cylindrostethinae, Gerrinae, and Ptilomerinae, which are subfamilies within Gerridae consisting of small-to-large bugs that have long and slender bodies, (2) Halobatinae, a subfamily within Gerridae, consisting of small-to-medium bugs with wide heads and thoraxes as well as short abdomens, and (3) Veliidae, which are small bugs with stout bodies. Estimation used five fitting functions – linear regression, polynomial regression order 2, 3, and 4, and power regression – on the following groupings: three body forms combined; each body form with life stages (juvenile and adult) combined; and each body form with life stages separated. Power regressions were the best fit in predicting the biomass of semi-aquatic bugs across life stages and body forms, and the predictive power of models was higher when the biomass of different body forms was calculated separately (specifically for Halobatinae and Veliidae). Splitting by life stages did not always result in additional improvement. The equations from this study expand the scope of possible future ecological research on semi-aquatic bugs, particularly in Southeast Asia, by allowing more studies to consider biomass-related questions.     

Preliminary study on heavy metals contamination of soil using solid phase speciation and the influence on groundwater in Bozanta–Baia Mare Area,Romania

Abstract

A preliminary study on soil contamination with heavy metals and As based on solid phase speciation according to the Tessier scheme and the influence on groundwater in an area under anthropogenic influence (Bozanta-Baia Mare, Romania) was conducted. The partitioning of Al, As, Cd, Cu, Fe, Mn, Pb and Zn in five fractions is discussed in relation to soil characteristics, pH, organic matter content, mineralogical composition and distribution of the same elements in airborne particulate matter. The airborne particulate matter contains high quantities of As, Cd, Cu, Pb and Zn as exchangeable fraction. The sequential extraction carried out on soil samples revealed the main role of Fe-Mn oxides surface in the immobilization of metals. Organic matter has a specific role in complexation of Cu, Pb, As and Al, since high contents of these metals were recovered in the oxidizable fraction. Cadmium has a high selectivity for carbonate minerals. The amendment of soil with natural fertilizer increases the exchangeable fraction of metals with the highest toxicity. The available fraction for plants (exchangeable + carbonate-bound species) exceeded the alert values in soil, therefore the continuous monitoring of the area is necessary. The soil is unsuitable for agricultural use due to high contamination on surface with toxic elements resulted from anthropogenic activities. Groundwater is contaminated with very toxic elements (As, Cd and Pb) but also with Cu, Mn and Zn and is unsuitable as supply for drinking water.