Using cheese whey for hydrogen and methane generation in a two-stage continuous process with alternative pH controlling approaches

This study focuses on the exploitation of cheese whey as a source for hydrogen and methane, in a two-stage continuous process. Mesophilic fermentative hydrogen production from undiluted cheese whey was investigated at a hydraulic retention time (HRT) of 24 h. Alkalinity addition (NaHCO₃) or an automatic pH controller were used, to maintain the pH culture at a constant value of 5.2. The hydrogen production rate was 2.9 ± 0.2 L/Lreactor/d, while the yield of hydrogen produced was approximately 0.78 ± 0.05 mol H₂/mol glucose consumed, with alkalinity addition, while the respective values when using pH control were 1.9 ± 0.1 L/Lreactor/d and 0.61 ± 0.04 mol H₂/mol glucose consumed. The corresponding yields of hydrogen produced were 2.9 L of H₂/L cheese whey and 1.9 L of H₂/L cheese whey, respectively. The effluent from the hydrogenogenic reactor was further digested to biogas in a continuous mesophilic anaerobic bioreactor. The anaerobic digester was operated at an HRT of 20d and produced approximately 1 L CH₄/d, corresponding to a yield of 6.7 L CH₄/L of influent. The chemical oxygen demand (COD) elimination reached 95.3% demonstrating that cheese whey could be efficiently used for hydrogen and methane production, in a two-stage process.     

Characterization of cellulolytic enzymes and bioH2 production from anaerobic thermophilic Clostridium sp. TCW1

A thermophilic anaerobic bacterium Clostridium sp. TCW1 was isolated from dairy cow dung and was used to produce hydrogen from cellulosic feedstock. Extracellular cellulolytic enzymes produced from TCW1 strain were identified as endoglucanases (45, 53 and 70 kDa), exoglucanase (70 kDa), xylanases (53 and 60 kDa), and β-glucosidase (45 kDa). The endoglucanase and xylanase were more abundant. The optimal conditions for H₂ production and enzyme production of the TCW1 strain were the same (60 °C, initial pH 7, agitation rate of 200 rpm). Ten cellulosic feedstock, including pure or natural cellulosic materials, were used as feedstock for hydrogen production by Clostridium strain TCW1 under optimal culture conditions. Using filter paper at 5.0 g/L resulted in the most effective hydrogen production performance, achieving a H₂ production rate and yield of 57.7 ml/h/L and 2.03 mol H₂/mol hexose, respectively. Production of cellulolytic enzyme activities was positively correlated with the efficiency of dark-H₂ fermentation.     

Hydrogen production by the newly isolated Clostridium beijerinckii RZF-1108

A fermentative hydrogen-producing strain, RZF-1108, was isolated from a biohydrogen reactor, and identified as Clostridium beijerinckii on the basis of the 16S rRNA gene analysis and physiobiochemical characteristics. The effects of culture conditions on hydrogen production by C. beijerinckii RZF-1108 were investigated in batch cultures. The hydrogen production and growth of strain RZF-1108 were highly dependent on temperature, initial pH and substrate concentration. Yeast extract was a favorable nitrogen source for hydrogen production and growth of RZF-1108. Hydrogen production corresponded to cell biomass yield in different culture conditions. The maximum hydrogen evolution, yield and production rate of 2209 ml H₂/l medium, 1.97 mol H₂/mol glucose and 104.20 ml H₂/g CDW h⁻¹ were obtained at 9 g/l of glucose, initial pH of 7.0, inoculum volume of 8% and temperature of 35 °C, respectively. These results demonstrate that C. beijerinckii can efficiently produce H₂, and is another model microorganism for biohydrogen investigations.     

Hybrid nanofibrous yarns based on N-carboxyethylchitosan and silver nanoparticles with antibacterial activity prepared by self-bundling electrospinning

Hybrid nanofibrous materials with antibacterial activity consisting of yarns from N-carboxyethylchitosan (CECh) and poly(ethylene oxide) (PEO) that contain 5 wt % or 10 wt % silver nanoparticles (AgNPs) were prepared. This was achieved by electrospinning using formic acid as a solvent and as a reducing agent for silver ions. AgNO₃ was used as an Ag⁺-containing salt. Its concentration was selected to be 0.02 mol/L or 0.04 mol/L in order the content of the AgNPs in the electrospun nanofibers to be 5 wt % or 10 wt %, respectively. The self-bundling of the fibers into yarns with a mean diameter of ca. 35 μm was enabled only by using a grounded needle electrode. The reduction of the silver ions to an elemental silver was evidenced by UV-vis spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The transmission electron microscopy (TEM) analyses revealed that AgNPs formed at AgNO₃ concentration of 0.02 mol/L were with a mean diameter of 4 ± 0.5 nm and were distributed uniformly within the fiber. The increase of AgNO₃ concentration to 0.04 mol/L led to the preparation of AgNPs with a higher mean diameter and a broader diameter distribution as well as to aggregate formation. The performed studies on the antibacterial activity of CECh/PEO/AgNPs fibrous materials against Staphylococcus aureus showed that at AgNPs content of 5 wt % the mats had bacteriostatic, and at AgNPs content of 10 wt %—bactericidal activity.     

Effects of key operational parameters on biohydrogen production via anaerobic fermentation in a sequencing batch reactor

In this study, a series of tests were conducted in a 6 L anaerobic sequencing batch reactor (ASBR) to investigate the effect of pH, hydraulic retention time (HRT) and organic loading rate on biohydrogen production at 28 °C. Sucrose was used as the main substrate to mimic carbohydrate-rich wastewater and inoculum was prepared from anaerobic digested sludge without pretreatment. The reactor was operated initially with nitrogen sparging to form anaerobic condition. Results showed that methanogens were effectively suppressed. The optimum pH value would vary depending on the HRT. Maximum hydrogen production rate and yield of 3.04 L H₂/L reactor d and 2.16 mol H₂/mol hexose respectively were achieved at pH 4.5, HRT 30 h, and OLR 11.0 kg/m³ d. Two relationships involving the propionic acid/acetic acid ratio and ethanol/acetic acid ratio were derived from the analysis of the metabolites of fermentation. Ethanol/acetic acid ratio of 1.25 was found to be a threshold value for higher hydrogen production.     

Hydrogen production by immobilized R. faecalis RLD-53 using soluble metabolites from ethanol fermentation bacteria E. harbinense B49

In order to increase the hydrogen yield from glucose, hydrogen production by immobilized Rhodopseudomonas faecalis RLD-53 using soluble metabolites from ethanol fermentation bacteria Ethanoligenens harbinense B49 was investigated. The soluble metabolites from dark-fermentation mainly were ethanol and acetate, which could be further utilized for photo-hydrogen production. Hydrogen production by B49 was noticeably affected by the glucose and phosphate buffer concentration. The maximum hydrogen yield (1.83 mol H₂/mol glucose) was obtained at 9 g/l glucose. In addition, we found that the ratio of acetate/ethanol (A/E) increased with increasing phosphate buffer concentration, which is favorable to further photo-hydrogen production. The total hydrogen yield during dark- and photo-fermentation reached its maximum value (6.32 mol H₂/mol glucose) using 9 g/l glucose, 30 mmol/l phosphate buffers and immobilized R. faecalis RLD-53. Results demonstrated that the combination of dark- and photo- fermentation was an effective and efficient process to improve hydrogen yield from a single substrate.     

Protective effect of piperine on electrophysiology abnormalities of left atrial myocytes induced by hydrogen peroxide in rabbits

Aims

Piperine had protective effects on oxidative stress damage of ventricular myocytes by hydrogen peroxide (H₂O₂). In this study we aimed to explore the protective effect of piperine on abnormalities of the cardiac action potential (AP) and several ion currents induced by hydrogen peroxide (H₂O₂) in single rabbit left atrial myocyte.

Main methods

Conventional microelectrodes were used to record action potential duration (APD), resting membrane potential (RMP) and some ion currents (I_Ca,L,I_to,I_K1 and I_kur,ect.), before and after H₂O₂ administration with or without piperine.

Key findings

The piperine (7 μmol/L) had no significant effect on APD, I_Ca,L,I_to,I_K1 and I_kur and their channel dynamics. In the presence of 50 μmol/L H₂O₂, APD₅₀ and APD₉₀ shortened (P < 0.01), amplitude of RMP decreased (P < 0.05), the peak of I_Ca,L reduced significantly (P < 0.05). Piperine (7 μmol/L) significantly alleviated the inhibiting effect of H₂O₂ on APD and I_Ca,L (P < 0.01) and protected the changes of I_Ca,L dynamics induced by H₂O₂. The peak current of I_to was reduced significantly (P < 0.05); Piperine (7 μmol/L) significantly alleviated the inhibiting effect of H₂O₂ on I_to (P < 0.01). In addition, piperine protected the changes of I_to dynamics induced by H₂O_2. The peak current of I_K1 and I_KUr was significantly reduced (P < 0.05); Piperine (7 μmol/L) alleviated the inhibiting effect of H₂O₂ on I_K1 and I_KUr significantly (P < 0.01). In addition, piperine protected the changes of I_KUr dynamics induced by H₂O₂.

Significance

These results suggest that piperine effectively protects atrial myocytes from oxidative stress injury in atrial electrophysiology.     

Effects of initial lactic acid concentration, HRTs, and OLRs on bio-hydrogen production from lactate-type fermentation

A batch test and continuous operation were performed to identify the effect of lactate on hydrogen production at pH 4.5. When the initial lactic acid concentration was increased from 0 to 8 g/L in the batch test, the hydrogen yield also increased from 1.41 to 1.72 mol-H₂/mol-glucose. The system exhibited a long lag time and an insignificant hydrogen yield with 16 g-lactic acid/L. A continuous stirred tank reactor (CSTR) was operated at different organic loading rates (OLRs: 10, 15, 20 and 40 g/L/day) and hydraulic retention times (HRTs: 6, 12 and 24 h). At an OLR of 20 g-glucose/L/day and 12 h of HRT, the hydrogen yield was 1.2 mol-H₂/mol-glucose. The yield decreased with a 24 h HRT. Even though lactate was one of the major constituents of volatile fatty acids (VFAs), hydrogen production was feasible throughout the operation. Clostridium sp. was the dominant hydrogen-producing bacteria in the system.     

Hydrolysis of lignocellulosic feedstock by novel cellulases originating from Pseudomonas sp. CL3 for fermentative hydrogen production

A newly isolated indigenous bacterium Pseudomonas sp. CL3 was able to produce novel cellulases consisting of endo-β-1,4-d-glucanase (80 and 100 kDa), exo-β-1,4-d-glucanase (55 kDa) and β-1,4-d-glucosidase (65 kDa) characterized by enzyme assay and zymography analysis. In addition, the CL3 strain also produced xylanase with a molecular weight of 20 kDa. The optimal temperature for enzyme activity was 50, 45, 45 and 55 °C for endo-β-1,4-d-glucanase, exo-β-1,4-d-glucanase, β-1,4-d-glucosidase and xylanase, respectively. All the enzymes displayed optimal activity at pH 6.0. The cellulases/xylanase could hydrolyze cellulosic materials very effectively and were thus used to hydrolyze natural agricultural waste (i.e., bagasse) for clean energy (H₂) production by Clostridiumpasteurianum CH4 using separate hydrolysis and fermentation process. The maximum hydrogen production rate and cumulative hydrogen production were 35 ml/L/h and 1420 ml/L, respectively, with a hydrogen yield of around 0.96 mol H₂/mol glucose.     

Spectrophotometric quantification of horseradish peroxidase with o-phenylenediamine

The assay conditions for the spectrophotometric quantification of horseradish peroxidase (HRP) with the chromogenic substrate o-phenylenediamine (OPD) at 25 °C in the presence of hydrogen peroxide (H₂O₂) were optimized. With [OPD]₀ = 3.14 mM and [H₂O₂]₀ = 80 μM at pH 7.2, the initial formation of only one of the possible reaction products and intermediates, 2,3-diaminophenazine (DAP, λ_max = 417 nm), was observed. The rate of DAP formation during the first 30 min of reaction was followed spectrophotometrically and found to linearly depend on the HRP concentration between 5 and 45 pM under the conditions used.     

Hydrogen production by Rhodopseudomonas palustris WP 3-5 in a serial photobioreactor fed with hydrogen fermentation effluent

In this study, a lab-scale serial photobioreactor composed of three column reactors was constructed and continuously operated to investigate several parameters influencing photohydrogen production when using the synthetic wastewater and the anaerobic hydrogen fermentation effluents as the influents. The results indicated that better hydrogen production rate was obtained when the serial photobioreactor was operated under cellular recycling at a short HRT of 8 h. The serial photobioreactor maintained high hydrogen content ca. 80% in the produced gas and 0.4× dilution ratio was the suitable ratio for hydrogen production. When the photobioreactor fed with the real wastewater (Effluent 1) containing 100 mg/L NH₄Cl, Column 1 reactor successfully reduced ammonia concentration to about 60 mg/L for cell synthesis, resulting in a steady hydrogen production in the following two column reactors. The average hydrogen production rate was 205 mL-H₂/L/d.     

Biosorption of reactive dye by waste biomass of Nostoc linckia

Potential of spent biomass of a cyanobacterium, Nostoc linckia HA 46, from a hydrogen bioreactor was studied for biosorption of a textile dye, reactive red 198. The waste biomass was immobilized in calcium alginate and used for biosorption of the dye from aqueous solution using response surface methodology (RSM). Kinetics of the dye in aqueous solution was studied in batch mode. Interactive effects of initial dye concentration (100-500 mg/L), pH (2-6) and temperature (25-45 °C) on dye removal were examined using Box-Behnken design. Maximum adsorption capacity of the immobilized biomass was 93.5 mg/g at pH 2.0, initial concentration of 100 mg/L and 35 °C temperature, when 94% of the dye was removed. Fourier transform infrared (FT-IR) studies revealed that biosorption was mainly mediated by functional groups like hydroxyl, amide, carboxylate, methyl and methylene groups present on the cell surface.     

Nanopowders of 3D Ag coordination polymer: A new precursor for preparation of silver nanoparticles

Nanopowders of novel three-dimensional Ag^I coordination polymer, [Ag₂(μ₈-SB)]_n (1) [H₂SB = 4-[(4-hydroxyphenyl)sulfonyl]-1-benzenol] has been synthesized by the reaction of SB²⁻ and AgNO₃ by a sonochemical method. Reaction conditions, such as the concentration of the initial reagents and power of the ultrasonic device played important roles in the size, morphology and growth process of the final products. For the first time silver nanoparticles were synthesized from [Ag₂(μ₈-SB)]_n (1) coordination polymer by calcinations and hydrothermal methods. These nanopowders and nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM); transmission electron microscopy (TEM) and energy-dispersive X-ray spectra (EDS). Thermal stability and emission properties of nano and crystal samples of compound 1 were studied and compared with each other.     

Biohydrogen production in alkalithermophilic conditions: Thermobrachium celere as a case study

In the present work the hydrogenesis in the anaerobic alkalithermophilic bacterium Thermobrachium celere was studied. The impact of several factors on hydrogen production during glucose fermentation was investigated in batch conditions. The optimal hydrogen production occurred at pH_67 °C 8.2 with phosphate buffer concentration of 50 mM. Hydrogen yield reached the highest value of 3.36 mol H₂/mol glucose when the partial pressure in the gas headspace was reduced. Supplementation of nitrogen sources and iron affected hydrogen production. Under optimized conditions, the maximum H₂ accumulation and H₂ production rate were estimated to be respectively 124.3 mmol H₂/l culture and 20.7 mmol H₂/l/h. Considering the efficient and rapid hydrogen evolution, and the ability to grow in extreme environments, T. celere might be a good candidate for biohydrogen production in open (non-sterile) bioprocess system.     

Biohydrogen production in a three-phase fluidized bed bioreactor using sewage sludge immobilized by ethylene–vinyl acetate copolymer

Ethylene–vinyl acetate (EVA) copolymer was used to immobilize H₂-producing sewage sludge for H₂ production in a three-phase fluidized bed reactor (FBR). The FBR with an immobilized cell packing ratio of 10% (v/v) and a liquid recycle rate of 5 l/min (23% bed expansion) was optimal for dark H₂ fermentation. The performance of the FBR reactor fed with sucrose-based synthetic medium was examined under various sucrose concentration (C_so) and hydraulic retention time (HRT). The best volumetric H₂ production rate of 1.80 ± 0.02 H₂ l/h/l occurred at C_so = 40 g COD/l and 2 h HRT, while the optimal H₂ yield (4.26 ± 0.04 mol H₂/mol sucrose) was obtained at C_so = 20 g COD/l and 6 h HRT. The H₂ content in the biogas was stably maintained at 40% or above. The primary soluble metabolites were butyric acid and acetic acid, as both products together accounted for 74–83% of total soluble microbial products formed during dark H₂ fermentation.     

Investigation of Cr(VI) adsorption onto chemically treated Helianthus annuus: Optimization using Response Surface Methodology

In the present study, chemically treated Helianthus annuus flowers (SHC) were used to optimize the removal efficiency for Cr(VI) by applying Response Surface Methodological approach. The surface structure of SHC was analyzed by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Analysis (EDX). Batch mode experiments were also carried out to assess the adsorption equilibrium in aqueous solution. The adsorption capacity (q_e) was found to be 7.2 mg/g. The effect of three parameters, that is pH of the solution (2.0-7.0), initial concentration (10-70 mg/L) and adsorbent dose (0.05-0.5 g/100 mL) was studied for the removal of Cr(VI) by SHC. Box-Behnken model was used as an experimental design. The optimum pH, adsorbent dose and initial Cr(VI) concentration were found to be 2.0, 5.0 g/L and 40 mg/L, respectively. Under these conditions, removal efficiency of Cr(VI) was found to be 90.8%.     

Evaluation of bioenergy recovery processes treating organic residues from ethanol fermentation process

This study evaluates a two-stage bioprocess for recovering bioenergy in the forms of hydrogen and methane while treating organic residues of ethanol fermentation from tapioca starch. A maximum hydrogen production rate of 0.77 mmol H₂/g VSS/h can be achieved at volumetric loading rate (VLR) of 56 kg COD/m³/day. Batch results indicate that controlling conditions at S₀/X₀ = 12 with X₀ = 4000 mg VSS/L and pH 5.5-6 are important for efficient hydrogen production from fermentation residues. Hydrogen-producing bacteria enriched in the hydrogen bioreactor are likely utilizing lactate and acetate for biohydrogen production from ethanol-fermentation residues. Organic residues remained in the effluent of hydrogen bioreactor can be effectively converted to methane with a rate of 0.37 mmol CH₄/g VSS/h at VLR of 8 kg COD/m³/day. Approximately 90% of COD in ethanol-fermentation residues can be removed and among that 2% and 85.1% of COD can be recovered in the forms of hydrogen and methane, respectively.     

Isolation,identification and characterization of a novel Rhodococcus sp. strain in biodegradation of tetrahydrofuran and its medium optimization using sequential statistics-based experimental designs

Statistics-based experimental designs were applied to optimize the culture conditions for tetrahydrofuran (THF) degradation by a newly isolated Rhodococcus sp. YYL that tolerates high THF concentrations. Single factor experiments were undertaken for determining the optimum range of each of four factors (initial pH and concentrations of K₂HPO₄ · 3H₂O, NH₄Cl and yeast extract) and these factors were subsequently optimized using the response surface methodology. The Plackett–Burman design was used to identify three trace elements (Mg²⁺, Zn²⁺and Fe²⁺) that significantly increased the THF degradation rate. The optimum conditions were found to be: 1.80 g/L NH₄Cl, 0.81 g/L K₂HPO₄ · 3H₂O, 0.06 g/L yeast extract, 0.40 g/L MgSO₄ · 7H₂O, 0.006 g/L ZnSO₄ · 7H₂O, 0.024 g/L FeSO₄ · 7H₂O, and an initial pH of 8.26. Under these optimized conditions, the maximum THF degradation rate increased to 137.60 mg THF h⁻¹ g dry weight in Rhodococcus sp. YYL, which was nearly five times of that by the previously described THF degrading Rhodococcus strain.     

Immobilization of catalase via adsorption onto metal-chelated affinity cryogels

A poly (acrylamide-allylglycidyl ether) [p(AAm-AGE)] cryogel was prepared by radical polymerization of acrylamide (AAm) and allylglycidyl ether (AGE). Cibacron Blue F3GA (CB) was covalently attached to the p(AAm-AGE) cryogel via the reaction between the chloride groups of the reactive dyes and the epoxide groups of the AGE. The CB-attached p(AAm-AGE) cryogel was chelated with Fe³⁺ ions. This immobilized metal ion affinity chromatography (IMAC) cryogel carrying 25.8 ± 2.0 μmol Fe³⁺ ions was used in adsorption studies to interrogate the effects of pH, protein initial concentration, flow rate, temperature and ionic strength on enzyme activity. Maximum adsorption capacities were found to be 75.7 ± 1.2 mg/g for p(AAm-AGE)-CB-Fe³⁺ cryogels and 60.6 ± 1.0 mg/g for p(AAm-AGE)-CB cryogels, respectively. The adsorbed amounts of catalase per unit mass of cryogel reached a plateau value at about 1.5 mg/mL at pH 6.0. The K_m values were found to be 0.73 ± 0.02 g/L for the free catalase and 0.18 ± 0.02 g/L for the immobilized catalase. The V_max value of free catalase (2.0 × 10³ U/mg enzyme) was found to be lower than that of the immobilized catalase (2.5 × 10³ U/mg enzyme). It was also observed that the enzyme could be repeatedly adsorbed and desorbed onto the p(AAm-AGE)-CB-Fe³⁺ cryogel.     

Biological hydrogen production by the algal biomass Chlorella vulgaris MSU 01 strain isolated from pond sediment

Chlorella vulgaris MSU 01 strain isolated from the sediment of the pond is able to produce molecular hydrogen in a clean way. To relate the dynamic coupling between the cultural conditions and biological responses, an original lab scale set up has been developed for hydrogen production. Different sources like mannitol, glucose, alanine, citric acid, aspartic acid, l-alanine, l-cysteine, sodium succinate and sodium pyruvate were used for algal media optimization. Corn stalk, from 1 to 5 g/L was tested for the effective algal growth and hydrogen production. The cell concentration of 1.6-19 g/L dry cell weight (DCW) was found at the 10th day. The kinetic parameters involved in the hydrogen production at 4 g/L corn stalk using the algal inoculum (50 mL) in the bioreactor volume (500 mL) was found to be with the hydrogen production potential (P_s) of 7.784 mL and production yield of (P_r) 5.534 mL respectively. The growth profile of the algal biomass at the above mentioned condition expressed the logistic model with R² 0.9988. The final pH of the broth was increased from 7.0 to 8.5-8.7. The anaerobic fermentation by C. vulgaris MSU 01 strain involved in the conversion process of complex carbon source has increased the H₂ evolution rate and higher butyrate concentration in the fermentate.