Effects of heat treatment on hydrogen production potential and microbial community of thermophilic compost enrichment cultures

Cellulosic plant and waste materials are potential resources for fermentative hydrogen production. In this study, hydrogen producing, cellulolytic cultures were enriched from compost material at 52, 60 and 70 °C. Highest cellulose degradation and highest H₂ yield were 57% and 1.4 mol-H₂ mol-hexose⁻¹ (2.4 mol-H₂ mol-hexose-degraded⁻¹), respectively, obtained at 52 °C with the heat-treated (80 °C for 20 min) enrichment culture. Heat-treatments as well as the sequential enrichments decreased the diversity of microbial communities. The enrichments contained mainly bacteria from families Thermoanaerobacteriaceae and Clostridiaceae, from which a bacterium closely related to Thermoanaerobium thermosaccharolyticum was mainly responsible for hydrogen production and bacteria closely related to Clostridium cellulosi and Clostridium stercorarium were responsible for cellulose degradation.     

Effects of biodrying process on municipal solid waste properties

In this paper, the effect of biodrying process on municipal solid waste (MSW) properties was studied. The results obtained indicated that after 14 d, biodrying reduced the water content of waste, allowing the production of biodried waste with a net heating value (NHV) of 16,779 ± 2,074 kJ kg⁻¹ wet weight, i.e. 41% higher than that of untreated waste. The low moisture content of the biodried material reduced, also, the potential impacts of the waste, i.e. potential self-ignition and potential odors production. Low waste impacts suggest to landfill the biodried material obtaining energy via biogas production by waste re-moistening, i.e. bioreactor. Nevertheless, results of this work indicate that biodrying process because of the partial degradation of the organic fraction contained in the waste (losses of 290 g kg⁻¹ VS), reduced of about 28% the total producible biogas.     

Dissimilatory perchlorate reduction: a review

In the United States anthropogenic activities are mainly responsible for the wide spread perchlorate contamination of drinking water, surface water, groundwater, and soil. Even at microgram levels, perchlorate causes toxicity to flora and fauna and affects growth, metabolism and reproduction in humans and animals. Reports of antithyroid effects of perchlorate and its detection in common food items have raised serious public health concerns, leading to extensive decontamination efforts in recent years. Several physico-chemical removal and biological decontamination processes are being developed. Although promising, ion exchange is a non-selective and incomplete process as it merely transfers perchlorate from water to the resin. The perchlorate-laden spent resins (perchlorate 200-500 mg L⁻¹) require regeneration resulting in production of concentrated brine (6-12% NaCl) or caustic waste streams. On the contrary, biological reduction completely degrades perchlorate into O₂ and innocuous Cl⁻. High reduction potential of ClO₄⁻/Cl⁻ (E° = ∼1.28 V) and ClO₃⁻/Cl⁻ pairs (E° = 1.03 V) makes these contaminants thermodynamically ideal e⁻ acceptors for microbial reduction. In recent years unique dissimilatory perchlorate reducing bacteria have been isolated and detailed studies pertaining to their microbiological, biochemical, genetics and phylogenetic aspects have been undertaken which is the subject of this review article while the various physico-chemical removal and biological reduction processes have been reviewed by others.     

Impacts of chlorination and heat shocks on growth, pigments and photosynthesis of Phaeodactylum tricornutum (Bacillariophyceae)

The main impacts of cooling water from thermal (nuclear) power plants on aquatic organisms were caused by chlorination and temperature increase. In this study, we investigated the impacts of residual chlorine and short-term heat shocks on growth, pigment contents and photosynthesis of Phaeodactylum tricornutum. Growth of P. tricornutum was completely inhibited; Chlorophyll a and carotenoids contents deceased about 63.3% and 61.4% in 24 h treated with 0.2 mg L^− 1 chlorine. The negative effects of chlorination increased with enhanced concentration and prolonged exposure time. Relative electrode transfer rate (rETR) of P. tricornutum was significantly suppressed when treated with 0.2 mg L^− 1 residual chlorine for 24 h. Furthermore, the effective quantum yield (F_v'/F_m') decreased first but then recovered with prolonged exposure when residual chlorine ranged between 0.1 and 0.2 mg L^− 1. The cells were less sensitive to heat shocks compared with chlorination: the rETR and F_v'/F_m' was suppressed only when the temperature exceeded 35 °C for 1 h. When P. tricornutum was exposed to chlorination combined with heat shocks, the rETR was further inhibited at 35 °C. It indicated that both chlorination and heat shocks had negative impacts on the primary producers living in discharging coastal waters; furthermore, there were synergistic effects of heat shocks on chlorination toxicity.     

Stimulating denitrification in a stream mesocosm with elemental sulfur as an electron donor

The heavy use of fertilizers in agricultural lands can result in significant nitrate (NO₃⁻) loadings to the aquatic environment. We hypothesized that biological denitrification in agricultural ditches and streams could be enhanced by adding elemental sulfur (S^o) to the sediment layer, where it could act as a biofilm support and electron donor. Using a bench-scale stream mesocosm with a bed of S^o granules, we explored NO₃⁻ removal fluxes as a function of the effluent NO₃⁻ concentrations. With effluent NO₃⁻ ranging from 0.5 mg N L⁻¹ to 4.1 mg N L⁻¹, NO₃⁻ removal fluxes ranged from 228 mg N m⁻² d⁻¹ to 708 mg N m⁻² d⁻¹. This is as much as 100 times higher than for agricultural drainage streams. Sulfate (SO₄²⁻) production was high due to aerobic sulfur oxidation. Molecular studies demonstrated that the S^o amendment selected for Thiobacillus species, and that no special inoculum was required for establishing a S^o-based autotrophic denitrifying community. Modeling studies suggested that denitrification was diffusion limited, and advective flow through the bed would greatly enhance NO₃⁻ removal fluxes. Our results indicate that amendment with S^o is an effective means to stimulate denitrification in a stream environment. To minimize SO₄²⁻ production, it may be better to place S^o deeper in the sediment layer.     

Biosensor based on the biocatalysis of microperoxidase-11 in nanocomposite material of multiwalled carbon nanotubes/room temperature ionic liquid for amperometric determination of hydrogen peroxide

A novel nanocomposite material of multiwalled carbon nanotubes (MWCNTs) and room temperature ionic liquid (RTIL) N-butylpyridinium hexafluorophosphate (BPPF₆) was explored and used to construct a novel microperoxidase-11 (MP-11) biosensor for the determination of hydrogen peroxide (H₂O₂). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the biosensor. Under the optimized experimental conditions, H₂O₂ could be detected in a linear calibration range of 0.5 to 7.0 × 10⁻⁷ mol L⁻¹ with a correlation coefficient of 0.9949 (n = 9) and a detection limit of 3.8 × 10⁻⁹ mol L⁻¹ at 3σ. The modified electrodes displayed excellent electrochemical response, high sensitivity, long-term stability, and good bioactivity and selectivity.     

2-phenylethanol (rose aroma) production potential of an isolated pichia kudriavzevii through solid-state fermentation

2-phenylethanol (2-PE) is a higher alcohol widely used in industry that can be obtained by solid-state fermentation (SSF) using low-cost raw materials. This report describes the 2-PE production potential of an indigenous Pichia kudriavzevii isolated from solid-state fermented sugarcane bagasse that possesses attractive characteristics for processing waste streams such as its low-pH tolerance, high growth rate and temperature resistance. Besides, 2-PE production was optimized in batch-SSF using sugarcane bagasse supplemented with l-phenylalanine as substrate. Full factorial design allowed identifying the pH adjustment, micronutrient addition, inoculum and co-substrate load effects, and response surface methodology served to identify the maximum production based on temperature, initial moisture content (MC₀) and specific airflow rate (S_AFR). While the pH adjustment and micronutrient addition did not affect the 2-PE production, temperature and MC₀ resulted critical for the process. After optimization, the maximum 2-PE content was 27.2 ± 0.2 mg per gram of dry substrate at 31 °C, 76 % MC₀ and 0.129 L h⁻¹ g⁻¹ S_AFR. This result was 23.8 % higher than the sub-optimal condition, and it is the highest 2-PE production via SSF reported so far. These results confirm the ability of P. kudriavzevii for producing 2-PE, and its potential for using waste streams as substrate.     

A kinetic evaluation of anaerobic treatment of swine wastewater at two temperatures in a temperate climate zone

A static granular bed reactor (SGBR) was used to treat swine wastewater at 24 and 16 °C. At 24 °C, the organic loading rate (OLR) was 0.7-5.4 kg COD/m³ day and the average chemical oxygen demand (COD) removal efficiency was 88.5%, respectively. Meanwhile, at 16 °C, the OLR was 1.6-4.0 kg COD/m³ day and the average COD removal efficiency was 68.0%, respectively. The SGBR acted as a bioreactor as well as a biofilter. After backwashing, the recovery of COD removal was not a function of an OLR but recovery time, while that of TSS removal was not a function of either recovery time or the OLR. The maximum substrate utilization rate (k_max) ratio was 1.89 between 24 and 16 °C, and the half velocity constant (K_s) ratio was 1.22, and the maximum specific growth rate (μ_max) ratio was 4.71. In addition, the temperature-activity coefficient in this study was determined to be 1.09.     

Life cycle assessment of biomass production in microalgae compact photobioreactors

This paper presents a life cycle assessment (LCA) of industrial scale microalgae biomass production in compact photobioreactor (PBR) systems (2 × 5 × 8 m) for supplying biofuel/electricity generation processes and synthesis of new materials. Other objectives are as follows: (i) to compare the impact of various raw materials, substances, and services; and (ii) to evaluate environment‐relevant aspects of the proposed system as compared to microalgae raceway ponds. The life cycle inventory assessment shows that (i) only atmospheric CO₂ is used for PBR microalgae cultivation, whereas in raceway ponds, injection of CO₂ from fossil origin is largely required to allow for microalgae growth; and (ii) the PBR daily production rate of dry biomass is currently at 1.5 kg m^?3 day^?1 for each PBR, which is 12.82 times larger than the reported average 0.117 kg m^?3 day^?1 raceway ponds production. It is found that in general the association of the effects of the production of steel, PVC, and the packaging contribute to more than 85% of the total impact in each analyzed category. Therefore, to achieve PBR biomass production impact reduction and sustainability, PVC and steel utilization need to be minimized, as well as packaging materials. Based on the PBR LCA results, that is, due to no CO₂ injection from fossil origin and low area occupation, it is expected that high density production of truly renewable microalgae biomass could be obtained from PBR systems.     

Multi-objective optimization of bioethanol production during cold enzyme starch hydrolysis in very high gravity cassava mash

Cold enzymatic hydrolysis conditions for bioethanol production were optimized using multi-objective optimization. Response surface methodology was used to optimize the effects of α-amylase, glucoamylase, liquefaction temperature and liquefaction time on S. cerevisiae biomass, ethanol concentration and starch utilization ratio. The optimum hydrolysis conditions were: 224 IU/g_starch α-amylase, 694 IU/g_starch glucoamylase, 77 °C and 104 min for biomass; 264 IU/g_starch α-amylase, 392 IU/g_starch glucoamylase, 60 °C and 85 min for ethanol concentration; 214 IU/g_starch α-amylase, 398 IU/g_starch glucoamylase, 79 °C and 117 min for starch utilization ratio. The hydrolysis conditions were subsequently evaluated by multi-objectives optimization utilizing the weighted coefficient methods. The Pareto solutions for biomass (3.655-4.380 × 10⁸ cells/ml), ethanol concentration (15.96-18.25 wt.%) and starch utilization ratio (92.50-94.64%) were obtained. The optimized conditions were shown to be feasible and reliable through verification tests. This kind of multi-objective optimization is of potential importance in industrial bioethanol production.     

Assessing amendment properties of digestate by studying the organic matter composition and the degree of biological stability during the anaerobic digestion of the organic fraction of MSW

The transformation of organic matter during anaerobic digestion of mixtures of energetic crops, cow slurry, agro-industrial waste and organic fraction of municipal solid waste (OFMSW) was studied by analysing different samples at diverse points during the anaerobic digestion process in a full-scale plant. Both chemical (fiber analysis) and spectroscopic approaches (¹³C CPMAS NMR) indicated the anaerobic digestion process proceeded by degradation of more labile fraction (e.g. carbohydrate-like molecules) and concentration of more recalcitrant molecules (lignin and non-hydrolysable lipids). These modifications determined a higher degree of biological stability of digestate with respect to the starting mixture, as suggested, also, by the good correlations found between the cumulative oxygen uptake (OD₂₀), and the sum of (cellulose + hemicellulose + cell soluble) contents of biomasses detected by fiber analysis (r = 0.99; P < 0.05), and both O–alkyl-C (r = 0.98; P < 0.05) and alkyl-C (r = −0.99; P < 0.05) measured by ¹³C CPMAS NMR.     

Continuous culture of the microalgae Schizochytrium limacinum on biodiesel-derived crude glycerol for producing docosahexaenoic acid

Crude glycerol is a major byproduct of the biodiesel industry; previous research has proved the feasibility of producing docosahexaenoic acid (DHA, 22:6 n − 3) through fermentation of the algae Schizochytrium limacinum on crude glycerol. The objective of this work is to investigate the cell growth kinetics, substrate utilization efficiency, and DHA production of the algae through a continuous culture. Steady-state biomass yield, biomass productivity, growth yield on glycerol, specific glycerol consumption rate, and fatty acid composition were investigated within the range of dilution rate (D) from 0.2 to 0.6 day⁻¹, and the range of feed crude glycerol concentration (S₀) from 15 to 120 g/L. The maximum specific growth rate was determined as 0.692 day⁻¹. The cells had a true growth yield of 0.283 g/g but with a relatively high maintenance coefficient (0.2216 day⁻¹). The highest biomass productivity of 3.88 g/L-day was obtained at D = 0.3 day⁻¹ and S₀ = 60 g/L, while the highest DHA productivity (0.52 g/L-day) was obtained at D = 0.3 day⁻¹ and S₀ = 90 g/L due to the higher DHA content at S₀ = 90 g/L. The biomass and DHA productivity of the continuous culture was comparable to those of batch culture, while lower than the fed-batch culture, mainly because of the lower DHA content obtained by the continuous culture. Overall, the results show that continuous culture is a powerful tool to investigate the cell growth kinetics and physiological behaviors of the algae growing on biodiesel-derived crude glycerol.     

Recombinant glucose oxidase from Penicillium amagasakiense for efficient bioelectrochemical applications in physiological conditions

GOX is the most widely used enzyme for the development of electrochemical glucose biosensors and biofuel cell in physiological conditions. The present work describes the production of a recombinant glucose oxidase from Penicillium amagasakiense (yGOXpenag) displaying a more efficient glucose catalysis (k_cat/K_M(glucose) = 93 μM⁻¹ s⁻¹) than the native GOX from Aspergillus niger (nGOXaspng), which is the most industrially used (k_cat/K_M(glucose) = 27 μM⁻¹ s⁻¹). Expression in Pichia pastoris allowed easy production and purification of the recombinant active enzyme, without overglycosylation. Its biotechnological interest was further evaluated by measuring kinetics of ferrocinium-methanol (FM_ox) reduction, which is commonly used for electron transfer to the electrode surface. Despite their homologies in sequence and structure, pH-dependant FM_ox reduction was different between the two enzymes. At physiological pH and temperature, we observed that electron transfer to the redox mediator is also more efficient for yGOXpenag than for nGOXaspng(k_cat/K_M(FM_ox) = 27 μM⁻¹ s⁻¹ and 17 μM⁻¹ s⁻¹ respectively). In our model system, the catalytic current observed in the presence of blood glucose concentration (5 mM) was two times higher with yGOXpenag than with nGOXaspng. All our results indicated that yGOXpenag is a better candidate for industrial development of efficient bioelectrochemical devices used in physiological conditions.     

Nitrogen uptake responses of Gracilaria vermiculophylla (Ohmi) Papenfuss under combined and single addition of nitrate and ammonium

The ammonium (NH₄⁺) and nitrate (NO₃⁻) uptake responses of tetrasporophyte cultures from a Portuguese population of Gracilaria vermiculophylla were studied. Thalli were incubated at 5 nitrogen (N) levels, including single (50 μM of NH₄⁺ or NO₃⁻) and combined addition of each of the N sources. For the combined additions, the experimental conditions attempted to simulate 2 environments with high N availability (450 μM NO₃⁻ + 150 μM NH₄⁺; 250 μM NO₃⁻ + 50 μM NH₄⁺) and the mean N concentrations occurring at the estuarine environment of this population (30 μM NO₃⁻ + 5 μM NH₄⁺). The uptake kinetics of NH₄⁺ and NO₃⁻ were determined during a 4 h time-course experiment with N deprived algae. The experiment was continued up to 48 h, with media exchanges every 4 h. The uptake rates and efficiency of the two N sources were calculated for each time interval. For the first 4 h, G. vermiculophylla exhibited non-saturated uptake for both N sources even for the highest concentrations used. The uptake rates and efficiency calculated for that period (V_0-4 h), respectively, increased and decreased with increasing substrate concentration. NO₃⁻ uptake rates were superior, ranging from 1.06 ± 0.1 to 9.65 ± 1.2 μM g(dw)⁻¹ h⁻¹, with efficiencies of 19% to 53%. NH₄⁺ uptake rates were lower (0.32 ± 0.0 to 5.75 ± 0.08 μM g(dw)⁻¹ h⁻¹) but G. vermiculophylla removed 63% of the initial 150 μM and 100% at all other conditions. Uptake performance of both N sources decreased throughout the duration of the experiment and with N tissue accumulation. Both N sources were taken up during dark periods though with better results for NH₄⁺. Gracilaria vermiculophylla was unable to take up NO₃⁻ at the highest concentration but compensated with a constant 27% NH₄⁺ uptake through light and dark periods. N tissue accumulation was maximal at the highest N concentration (3.9 ± 0.25% dw) and superior under NH₄⁺ (3.57 ± 0.2% dw) vs NO3 (3.06 ± 0.1% dw) enrichment. The successful proliferation of G. vermiculophylla in estuarine environments and its potential utilization as the biofilter component of Integrated Multi-Trophic Aquaculture (IMTA) are discussed.     

Purification and characterization of Put1p from Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the PUT1 and PUT2 genes are required for the conversion of proline to glutamate. The PUT1 gene encodes Put1p, a proline dehydrogenase (PRODH) enzyme localized in the mitochondrion. Put1p was expressed and purified from Escherichia coli and shown to have a UV-visible absorption spectrum that is typical of a bound flavin cofactor. A K_m value of 36 mM proline and a k_cat = 27 s⁻¹ were determined for Put1p using an artificial electron acceptor. Put1p also exhibited high activity using ubiquinone-1 (CoQ₁) as an electron acceptor with a k_cat = 9.6 s⁻¹ and a K_m of 33 μM for CoQ₁. In addition, knockout strains of the electron transfer flavoprotein (ETF) homolog in S. cerevisiae were able to grow on proline as the sole nitrogen source demonstrating that ETF is not required for proline utilization in yeast.     

Production of keratinolytic proteases through bioconversion of feather meal by the Amazonian bacterium Bacillus sp. P45

Extracellular keratinase production by the feather-degrading Amazonian isolate Bacillus sp. P45 was evaluated with various growth substrates. Higher enzyme production occurred with feather meal (FM) in comparison to casein, gelatin, and cheese whey, suggesting the specificity of this strain for the utilization of keratinous substrates. Supplementation of FM medium with carbohydrates reduced enzyme production, probably due to catabolite repression. Increased keratinase yield was achieved when NH₄Cl was added to FM medium. The effects of FM and NH₄Cl concentrations on enzyme production were investigated using a 2² central composite design. Feather meal was the most significant parameter, while NH₄Cl concentrations resulted in slight differences in enzyme yield. In the range studied, optimal concentrations of FM and NH₄Cl were 43-50 g l⁻¹ and 1.8-8.6 g l⁻¹, respectively, resulting in an effective low-cost medium for the production of keratinolytic protease. Crude keratinase showed maximum activity at 50 °C and pH 7.0, and was strongly inhibited by EDTA, indicating the importance of metal ions for activity/stability. The crude keratinase from mesophilic Bacillus sp. P45 could potentially be used in the bioconversion of recalcitrant keratinous wastes through an environmentally friendly and energy-saving process, producing protein hydrolysates with commercial value for utilization as animal feed and fertilizers.     

Understanding DP receptor antagonism using a CoMSIA approach

A Comparative Molecular Similarity Indices Analysis (CoMSIA) was performed for 2,6-substituted-4-monosubstituted aminopyrimidine antagonists of prostaglandin D₂ receptor (DP). Both two-component (Q² = 0.63, R² = 0.82, SEE = 0.47 pIC₅₀) and three-component (Q² = 0.70, R² = 0.91, SEE = 0.36 pIC₅₀) CoMSIA models were established. Two hydrogen-bond acceptors with spatial separation of about 8 Å are shown as optimal for binding. A large hydrophobic center that separates the two acceptors confers to the potency of the 2,6-substituted-4-monosubstituted aminopyrimidine. The models were used to predict IC₅₀ values for compounds which had functional groups different from those in the training set.     

Octahedral hexanuclear complexes involving light lanthanide ions

Two new hexanuclear complexes involving two of the lightest lanthanide ions have been synthesized and structurally described. Their chemical formula is [Ln₆(μ₆-O)(μ₃-OH)₈(NO₃)₆(H₂O)₁₄] · 2NO₃ · 2H₂O with Ln = Pr or Nd. The structure has been solved for the Pr³⁺-containing compound. It crystallizes in the monoclinic system, space group P21/n (no. 14) with a = 12.4163(2) Å, b = 10.51210(10) Å, c = 16.0389(2) Å, β = 95.7810(6)° and Z = 4. The chemical and thermal stabilities of both the compounds have been studied. These studies reveal that they can be used as molecular chemical precursors for further materials synthesis. To the best of our knowledge, this praseodymium-containing hexanuclear complex is the first ever reported.     

Kinetic studies on the first dihydrogen aquacomplex, [Ru(H2)(H2O)5]: Formation under H2 pressure and catalytic H/D isotope exchange in water

The ruthenium(II) hexaaqua complex [Ru(H₂O)₆]²⁺ reacts with dihydrogen under pressure to give the η²-dihydrogen ruthenium(II) pentaaqua complex [Ru(H₂)(H₂O)₅]²⁺.The complex was characterized by ¹H, ²H and ¹⁷O NMR: δ_H = −7.65 ppm, J_HD = 31.2 Hz, δ_O = −80.4 ppm (trans to H₂) and δ_O = −177.4 ppm (cis to H₂).The H-H distance in coordinated dihydrogen was estimated to 0.889 Å from J_HD, which is close to the value obtained from DFT calculations (0.940 Å).Kinetic studies were performed by ¹H and ²H NMR as well as by UV-Vis spectroscopy, yielding the complex formation rate and equilibrium constants: k_f = (1.7 ± 0.2) × 10⁻³ kg mol⁻¹ s⁻¹ and K_eq = 4.0 ± 0.5 mol kg⁻¹.The complex formation rate with dihydrogen is close to values reported for other ligands and thus it is assumed that the reaction with dihydrogen follows the same mechanisn (I_d).In deuterated water, one can observe that [Ru(H₂)(H₂O)₅]²⁺ catalyses the hydrogen exchange between the solvent and the dissolved dihydrogen.A hydride is proposed as the intermediate for this exchange.Using isotope labeling, the rate constant for the hydrogen exchange on the η²-dihydrogen ligand was determined as k₁ = (0.24 ± 0.04) × 10⁻³ s⁻¹.The upper and lower limits of the pK_a of the coordinated dihydrogen ligand have been estimated:3 < pK_a < 14.