Bubble behavior and photo-hydrogen production performance of photosynthetic bacteria in microchannel photobioreactor

A transparent microchannel photobioreactor was manufactured to visualize the colony formation of photosynthetic bacteria (PSB), Rhodopseudomonas palustris CQK 01, as well as the biogas bubble behavior within the microstructure. The results showed that the formation of PSB colony in the interior of microchannels can be divided into four stages: bacteria absorption, bacteria reproduction, morphological transformation and colony formation. It was founded that the microchannel vents immobilized by PSB colony was the favorable sites for the emergence of biogas bubbles. In this work, the effects of substrate concentration and flow rate of the influent solution as well as illumination wavelength and intensity on the photo-hydrogen production performance of the bioreactor were also investigated. The microchannel photobioreactor exhibited a maximal hydrogen production rate of 1.48 mmol/g cell dry weight/h, maximal hydrogen yield of 0.91 mol H₂/mol glucose in all tests at an optimal inlet medium flow rate of 2.8 ml/h and substrate concentration of 50 mmol/l. In addition, photobioreactor showed a highest performance of hydrogen production and substrate consumption at 590 nm illumination wavelength and 5000 lx illumination intensity.     

Mathematical modeling of two-phase flow and transport in an immobilized-cell photobioreactor

A one-dimensional two-phase flow and transport model is presented for a packed bed photobioreactor with transparent gel granules containing immobilized photosynthetic bacterial cells. The inherently coupled two-phase flow and mass transport, along with the biochemical reactions occurring in the photobioreactor are taken into account. The source term in the species conservation equation of the substrate is derived from a local transport model for a single gel granule. Model predictions of the glucose consumption efficiency and hydrogen production rate are in good agreement with experimental data. The results show that the photoinhibition of immobilized cells appears at incident light intensities higher than 6000 lux. It is the most suitable for photo-hydrogen production under neutral conditions and 30 °C of the influent substrate solution. Moreover, a high influent substrate solution flow rate results in a large hydrogen production rate due to the improved substrate transport from the bulk solution to gel granules.     

Effect of physico-chemical parameters on biohydrogen production and growth characteristics by batch culture of Rhodobacter sphaeroides CIP 60.6

In this paper, Rhodobacter sphaeroides CIP 60.6 strain was newly used for the biohydrogen production in a perfectly shaken column photobioreactor, grown in batch culture under anaerobic and illumination conditions, to investigate the effects of some physico-chemical parameters in microbial hydrogen photofermentation. Luedeking–Piret model was considered for the data fitting to find out the mode of hydrogen generation and the relationship between the cell growth and hydrogen production. The results show that, both growth cells and resting cells can produce hydrogen at light intensities greater or equal to 2500 lux, however, at the weak intensities hydrogen is a metabolite associated to growth. Growth rate and hydrogen production rate increase with the increasing of light intensity. Moreover, hydrogen production rate become higher in stationary phase than that in logarithmic phase, with the enhancement of light intensity. Maximum hydrogen production rate obtained was 39.88 ± 0.14 ml/l/h, at the optimal conditions (4500–8500 lux). Modified Gompertz equation was applied for the data fitting to verify the accuracy and the agreement of the model with experimental results. It is revealed that, in the modified Gompertz equation, the lag time represents time for which hydrogen production becomes maximal, not the beginning time of hydrogen production. The stop of stirring reduced hydrogen production rate and created unstable hydrogen production in reactor. The pH ranges of 7.5 ± 0.1 were the favorable pH for hydrogen production.     

Effect of culture conditions on the kinetics of hydrogen production by photosynthetic bacteria in batch culture

Biochemical kinetic characteristics of photo-fermentative hydrogen production were experimentally and numerically investigated to optimize the photo-fermentation hydrogen-producing process in this work. It is found that a maximum specific growth rate of 0.26 h⁻¹ was achieved under the optimal conditions of illumination intensity 6000 lux, 30 °C culture temperature and pH 7.0 of culture medium. These experimental results also led to an empirical formula of the maximum specific microbial growth rate (μ_max) as a function of illumination intensity, pH and temperature. With the empirical formula, the modified Monod equation along with the kinetic equations for biomass growth, glucose consumption and hydrogen production is then developed to simulate the photofermentation hydrogen-producing process. The modeling results are in good agreements with the experimental data, indicating that the developed kinetic models are able to objectively describe the characteristics of hydrogen production by PSB under different culture conditions.     

Visible-light-induced hydrogen production over Pt-Eosin Y catalysts with high surface area silica gel as matrix

A new system for the production of hydrogen, constructed using silica gel as a matrix, Eosin Y as a photosensitizer, and Pt as a cocatalyst, has been reported. It was found that the rate of photosensitized hydrogen evolution in the presence of silica gel is enhanced about 10-fold relative to the homogeneous phase, i.e. in the absence of silica gel. The pH value of the solution and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 7 and 3.60 × 10⁻⁴ mol dm⁻³ (E/S = 1/3) to 7.24 × 10⁻⁴ mol dm⁻³ (E/S = 1/1), respectively. Triethanolamine (TEOA) as an electron donor, the rate of hydrogen evolution and the apparent quantum efficiency in the silica gel system under visible-light irradiation (λ ≥ 420 nm) can reach about 43 μmol h⁻¹ and 10.4%, respectively. In addition, the roles of silica gel, Pt and TEOA, respectively; and the probable mechanism of photosensitized hydrogen evolution have been discussed.     

Lattice Boltzmann simulation of substrate solution through a porous granule immobilized PSB-cell for biohydrogen production

A bioreaction system of substrate solution through a porous granule immobilized photosynthetic bacteria-cell for photobiohydrogen production is simulated by the lattice Boltzmann model coupled with a multi-block strategy. The effects on flow and mass transfer are investigated by illumination intensity, influent velocity, permeability and porosity of porous granule. Additionally, hydrogen production performance including hydrogen yield and substrate consumption efficiency is evaluated. The numerical results indicate that the hydrogen yield and substrate consumption efficiency achieve maximum under illumination intensity of 6000 lx. The permeability and influent velocity have significant impact on flow and concentration fields. Moreover, with increasing permeability, the hydrogen yield increases, while the substrate consumption efficiency decreases, and with increasing influent velocity, both the hydrogen yield and consumption efficiency decrease. With increasing porosity, the hydrogen yield slightly decreases and the substrate consumption efficiency increases, and they tend to be stable when the porosity is over 0.5.     

The effect of Ni,Fe and Mg concentration on photo-hydrogen production by Rhodopseudomonas faecalis RLD-53

In the present study, the effect of Ni²⁺ (0–10 μmol/l), Fe²⁺ (0–200 μmol/l) and Mg²⁺ (0–15 mmol/l) concentration on photo-hydrogen production from acetate was investigated by batch culture. Results showed that under a proper concentration range, Ni²⁺ was able to enhance the hydrogen production rate and the hydrogen yield; Fe²⁺ was able to increase the hydrogen yield, and hydrogen production rate was enhanced only when the culturing time was 24–72 h. Ni²⁺ and Fe²⁺ at a higher concentration inhibited cell growth. When Ni²⁺ and Fe²⁺ concentrations were 4 μmol/l and 80 μmol/l, respectively, maximal hydrogen yield of 2.87 and 2.78 mol H₂/mol acetate was obtained when batch culturing at 35 °C with initial pH 7.0. Mg²⁺ did not significantly affect hydrogen production and hydrogen yield which maintained at about 2.45 mol H₂/mol acetate, but it was favorable to cell growth.     

Performance of a groove-type photobioreactor for hydrogen production by immobilized photosynthetic bacteria

The biofilm technique has been proved to be an effective cell immobilization method for wastewater biodegradation but it has had restricted use in the field of photobiological H₂ production. In the present study, a groove-type photobioreactor was developed and it was shown that a groove structure with large specific surface area was beneficial to cell immobilization and biofilm formation of the photosynthetic bacteria on photobioreactor surface as well as light penetration. A series of experiments was carried out on continuous hydrogen production in the groove-type photobioreactor illuminated by monochromatic LED lights and the performance was investigated. The effects of light wavelength, light intensity, inlet glucose concentration, flow rate and initial substrate pH were studied and the results were compared with those obtained in a flat panel photobioreactor. The experimental results show that the optimum operational conditions for hydrogen production in the groove-type photobioreactor were: inlet glucose concentration 10 g/L, flow rate 60 mL/h, light intensity 6.75 W/m², light wavelength 590 nm and initial substrate pH 7.0. The maximum hydrogen production rate, H₂ yield and light conversion efficiency in the groove-type photobioreactor were 3.816 mmol/m²/h, 0.75 molH₂/molglucose and 3.8%, respectively, which were about 75% higher than those in the flat panel photobioreactor.     

Control strategies for hydrogen production through co-culture of Ethanoligenens harbinense B49 and immobilized Rhodopseudomonas faecalis RLD-53

This study evaluated hydrogen production by co-culture of Ethanoligenens harbinense B49 and immobilized Rhodopseudomonas faecalis RLD-53 with different control strategies. To enhance cooperation of dark and photo-fermentation bacteria during hydrogen production process, the glucose concentration, phosphate buffer concentration and initial pH were controlled at 6 g/l, 50 mmol/l and 7.5, respectively. The maximum yield and rate of hydrogen production were 3.10 mol H₂/mol glucose and 17.2 mmol H₂/l/h, respectively. Ethanol from E. harbinense B49 in acetate medium can enhance hydrogen production by R. faecalis RLD-53 except the ratio of ethanol to acetate (R_E/A) among 0.8 to 1.0. Control of the proper phosphate buffer concentration (50 mmol/l) not only increased acetic acid production by E. harbinense B49, but also maintained stable pH of co-culture system. Therefore, the results showed that co-culture of E. harbinense B49 and immobilized R. faecalis RLD-53 was a promising way of converting glucose into hydrogen.     

Enhancement of phototrophic hydrogen production by Rhodobacter sphaeroides ZX-5 using a novel strategy — shaking and extra-light supplementation approach

Biohydrogen has gained attention due to its potential as a sustainable alternative to conventional methods for hydrogen production. In this study, the effect of light intensity as well as cultivation method (standing- and shaking-culture) on the cell growth and hydrogen production of Rhodobacter sphaeroides ZX-5 were investigated in 38-ml anaerobic photobioreactor with RCVBN medium. Thus, a novel shaking and extra-light supplementation (SELS) approach was developed to enhance the phototrophic H₂ production by R. sphaeroides ZX-5 using malate as the sole carbon source. The optimum illumination condition for shaking-culture by strain ZX-5 increased to 7000–8000 lux, markedly higher than that for standing-culture (4000–5000 lux). Under shaking and elevated illumination (7000–8000 lux), the culture was effective in promoting photo-H₂ production, resulting in a 59% and 56% increase of the maximum and average hydrogen production rate, respectively, in comparison with the culture under standing and 4000–5000 lux conditions. The highest hydrogen-producing rate of 165.9 ml H₂/l h was observed under the application of SELS approach. To our knowledge, this record is currently the highest hydrogen production rate of non-immobilized purple non-sulphur (PNS) bacteria. This optimal performance of photo-H₂ production using SELS approach is a favorable choice of sustainable and economically feasible strategy to improve phototrophic H₂ production efficiency.     

Inhibitory effect of ethanol,acetic acid,propionic acid and butyric acid on fermentative hydrogen production

The inhibitory effect of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35 °C and initial pH 7.0, during the fermentative hydrogen production, the substrate degradation efficiency, hydrogen production potential, hydrogen yield and hydrogen production rate all trended to decrease with increasing added ethanol, acetic acid, propionic acid and butyric acid concentration from 0 to 300 mmol/L. The inhibitory effect of added ethanol on fermentative hydrogen production was smaller than those of added acetic acid, propionic acid and butyric acid. The modified Han–Levenspiel model could describe the inhibitory effects of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production rate in this study successfully. The modified Logistic model could describe the progress of cumulative hydrogen production.     

Effect of temperature on fermentative hydrogen production by mixed cultures

Effect of temperatures ranging from 20 °C to 55 °C on fermentative hydrogen production by mixed cultures was investigated in batch tests. The experimental results showed that, at initial pH 7.0, during the fermentative hydrogen production using glucose as substrate, the substrate degradation efficiency and hydrogen production potential increased with increasing temperatures from 20 °C to 40 °C. The maximal substrate degradation efficiency was 98.1%, the maximal hydrogen production potential was 269.9 mL, the maximal hydrogen yield was 275.1 mL/g glucose and the shortest lag time was 7.0 h. The temperature for fermentative hydrogen production by mixed cultures was optimized to be 40 °C. The expanded Ratkowsky models could be used to describe the effect of temperatures on the hydrogen production potential, maximum hydrogen production rate and the lag time during fermentative hydrogen production.     

Pretreatment of methanogenic granules for immobilized hydrogen fermentation

Hydrogen can be produced through fermenting sugars in a mixed bacterial culture under anaerobic conditions. Anaerobic granular sludge was proposed as immobilized hydrogen producing bacteria to be used in hydrogen fermentation after methanogenic activity of the granule was eliminated in the pretreatment process. This paper reports an innovative treatment method to directly convert methanogenic granules to hydrogen producing granules using chloroform. Chloroform treatment was compared against acid and heat treatments of sewage sludge and methanogenic granules in terms of effectiveness to eliminate methanogenic activity. The results showed that chloroform treatment was the most effective among the three methods tested. Acid and heat treatments that were effective for sewage sludge treatment were observed not highly effective for application to granules because of the protection from the granular structure. In contrast, methanogens were very sensitive to the chloroform even at very low level. Methane production was almost completely inhibited in both sewage sludge and granules with the treatment with only 0.05% chloroform addition into the culture medium. If the chloroform concentration was controlled at low levels, chloroform selectively inhibited methanogenic activity while did not affect the hydrogen production. At high concentration range, chloroform also inhibited hydrogen production. Chloroform caused irreversible methanogenic activity elimination but hydrogen production recovered to normal after chloroform addition stopped. Chloroform showed desirable selectivity on inhibition of methanogens from hydrogen producing bacteria, nearly permanently eliminated the methane production, postponed the hydrogen consumption to acetic acid, while allowed recovery for normal hydrogen production. Chloroform treated granules were repeatedly cultured for eight time without noticeable damage. Continuous culture with chloroform treated granules showed that the granule structure could be kept for over 15 days and new granules started to form after 10 days operation. The hydrogen productivity reached 11.6 L/L/day at HRT 5.3 h, which all showed potential application of chloroform treatment of methanogenic granules in the immobilized hydrogen fermentation.     

Enhancement of biohydrogen producing using ultrasonication

Ultrasonication was evaluated as a pretreatment for biological hydrogen production from glucose in batch studies, in comparison with heat-shock pretreatment, acid pretreatment, and base pretreatment. The optimized sonication energy for hydrogen production using anaerobic digester sludge was 79 kJ/gTS. Sonication with temperature control (less than 30 °C) increased volumetric hydrogen production by 120% over the untreated sludge, and by 40% over the heat-shock and acid pretreated sludge, with a marginal (∼10%) increase in hydrogen production rate. Upon comparing the molar hydrogen yield in sonicated sludge with and without temperature control, the deleterious effect of heat on some hydrogen producers as reflected by a 30% decrease in yield to 1.03 mol H₂/mol glucose is evident. Sonication with temperature control affected a 45% increase in molar hydrogen yield to 1.55 mol H₂/mol glucose over heat-shock pretreatment at 70 °C for 30 min and acidification to pH 3.0 for 24 h at 4 °C. Sonication with temperature control produced a biomass yield of 0.13 g VSS/g COD, as compared to 0.24 g VSS/g COD for the untreated sludge. The hydrogen yield increased linearly with the molar acetate to butyrate ratio and decreased linearly with the biomass yield.     

Effects of vitamins (nicotinic acid, vitamin B1 and biotin) on phototrophic hydrogen production by Rhodobacter sphaeroides ZX-5

The effects of vitamins (nicotinic acid, vitamin B₁ and biotin) on the growth and hydrogen production of Rhodobacter sphaeroides ZX-5 were investigated by batch culture in this study. The results showed that nicotinic acid, as a precursor of NAD⁺/NADH, plays a crucial role in effectively enhancing the phototrophic hydrogen synthesis during photo-fermentation process. Lack of nicotinic acid in hydrogen production medium resulted in the failure of photo-hydrogen production. In addition, though vitamin B₁ and biotin do not have direct impact on photo-hydrogen production, they are still essential and must exist in either growth medium or hydrogen production medium. Without either of them, photo-hydrogen production decreased seriously, regardless of the existence of nicotinic acid.     

Development of a compact high-density microbial hydrogen reactor for portable bio-fuel cell system

The development of a compact high-density microbial reactor for hydrogen production is described with possible implications to use as a portable bio-fuel cell system. To construct the compact bioreactor, mainly, the cell density and immobilization methods were optimized in this paper. The encapsulation of hydrogen producing bacterium, Escherichia coli strain MC13-4, in alginate gel beads provided approximately three-fold increase in hydrogen production in comparison with the free cell suspension. The immobilized cells (cell density; O.D. 100) and 500 mM glucose solution were packed into a 20 mL glass bottle that was connected to the fuel cell. This system has generated electricity of over 20 mW for 20 min.     

Biohydrogen production by Clostridium butyricum EB6 from palm oil mill effluent

A hydrogen producer was successfully isolated from anaerobic digested palm oil mill effluent (POME) sludge. The strain, designated as Clostridium butyricum EB6, efficiently produced hydrogen concurrently with cell growth. A controlled study was done on a synthetic medium at an initial pH value of 6.0 with 10 g/L glucose with the maximum hydrogen production at 948 mL H₂/L-medium and the volumetric hydrogen production rate at 172 mL H₂/L-medium/h. The supplementation of yeast extract was shown to have a significant effect with a maximum hydrogen production of 992 mL H₂/L-medium at 4 g/L of yeast extract added. The effect of pH on hydrogen production from POME was investigated. Experimental results showed that the optimum hydrogen production ability occurred at pH 5.5. The maximum hydrogen production and maximum volumetric hydrogen production rate were at 3195 mL H₂/L-medium and 1034 mL H₂/L-medium/h, respectively. The hydrogen content in the biogas produced was in the range of 60–70%.     

固定化光合细菌处理有机废水过程产氢的研究——Ⅱ.红假单胞菌菌株D利用有机物光产氢的特性

应用固定化细胞技术,研究红假单胞菌菌株D(Rhodopseudomonas sp.D)利用有机物光产氢的过程特性,发现以琼脂包埋的固定化细胞,在以苹果酸作为基质的条件下,光照培养120h,总产氢量达到119.5ml,产氢速率为19.92ml(1·h)~(-1)。与悬浮细胞相比,产氢能力提高90％,而且光产氢持续时时延长。菌体菌龄、颗粒内生物量、光照强度、光照/黑暗时间、基质初始pH以及基质浓度均影响产氢过程。试验还证实除苹果酸外,废水中常见污染物如葡萄糖、乳酸、丙酸也是良好的产氢基质。本实验结果表明用光合细菌处理有机废水同时回收氢能的可能性。     

Fermentative hydrogen production by the newly isolated Clostridium beijerinckii Fanp3

A hydrogen producing strain newly isolated from anaerobic sludge in an anaerobic bioreactor, was identified as Clostridium beijerinckii Fanp3 by 16S rDNA gene sequence analysis and detection by BioMerieux Vitek. The strain could utilize various carbon and nitrogen sources to produce hydrogen, which indicates that it has the potential of converting renewable wastes into hydrogen. In batch cultivations, the optimal initial pH of the culture medium was between 6.47 and 6.98. Using 0.15 M phosphate as buffer could alleviate the medium acidification and improve the overall performance of C. beijerinckii Fanp3 in hydrogen production. Culture temperature of 35 °C was established to be the most favorable for maximum rate of hydrogen production. The distribution of soluble metabolic products (SMP) was also greatly affected by temperature. Considering glucose as a substrate, the activation energy (E_a) for hydrogen production was calculated as 81.01 kcal/mol and 21.4% of substrate energy was recovered in the form of hydrogen. The maximal hydrogen yield and the hydrogen production rate were obtained as 2.52 mol/mol-glucose and 39.0 ml/g-glucose h⁻¹, respectively. These results indicate that C. beijerinckii Fanp3 is an ideal candidate for the fermentative hydrogen production.     

Biological hydrogen production from steam-exploded straw by simultaneous saccharification and fermentation

Hydrogen was produced by simultaneous saccharification and fermentation from steam-exploded corn straw (SECS) using Clostridium butyricum AS1.209. Effect of various process parameters, such as solid to liquid ratio, enzyme loading and initial pH, etc., were examined with respect to maximum hydrogen productivity which was obtained by fitting the cumulative hydrogen production data to a modified Gompertz equation. Maximum specific hydrogen production rate and maximal hydrogen yield were 126 ml/g VSS d and 68 ml/g SECS, respectively. The yield of soluble metabolites was 197.7 mg/g SECS. Acetic acid accounted for 46% of the total was the most abundant product and this shows that hydrogen production from SECS was essentially acetate-type fermentation. Hydrogen production by simultaneous saccharification and fermentation of SECS has the predominance of short lag-stage and high maximum specific hydrogen production rate and it was a promising method for hydrogen production and straw biomass conversion.