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[Display omitted] • The titanate was combined with photo fermentative hydrogen production (PFHP). • Adding titanate significantly improved the efficiency of PFHP. • Adding titanate can shorten the hydrogen production delay period. • The addition of titanate can promote the utilization of Volatile fatty acids. • The cumulative hydrogen production by adding MgTiO 3 increased by 48.3%. The effects of three common titanate photocatalysts (TPC) on the photo fermentation biohydrogen production (PFHP) from corn stover were studied in this paper. Compared with CaTiO 3 and BaTiO 3 , the experimental group with the addition of MgTiO 3 showed stronger potential for PFHP, the maximum hydrogen yield of 344 mL (68.8 mL/g TS) was obtained at 3 g/L MgTiO 3 , increased by 48.3%. For CaTiO 3 , BaTiO 3 , the optimal amount of addition was 8 and 7 g/L, respectively, in which, the hydrogen yield was 308 and 288 mL (61.6 and 57.6 mL/g TS). TPC addition could shorten the delay period of hydrogen production lower the Oxidation-Reduction Potential (ORP) of fermentation broth, especially MgTiO 3 addition, the delayed hydrogen production could be shortened by 33.2% compared with control group, and the ORP could reach the lowest value of −371 mV. [ABSTRACT FROM AUTHOR]

[Display omitted] • The torrefaction pretreatment was applied in enhancing corn stover degradation. • Torrefaction pretreated corn stover reached highest hydrolysis efficiency at 200℃. • Reducing sugars and hydrogen yield increased by 46.41% and 70.79%. • Torrefaction pretreatment shorten the lag phase time of hydrogen production. The torrefaction pretreatment technology with different temperature varying from 160℃ to 240℃ was utilized to enhance the enzymatic saccharification and hydrogen production potential of corn stover. The composition characteristics, Crystal Intensity (CrI), reducing sugars yield and hydrogen production of the pretreated corn stover were detected to explore the torrefaction pretreatment effectiveness. Results revealed that the reducing sugar yield and hydrogen production from corn stover were improved significantly through torrefaction pretreatment, both the maximum reducing sugar yield of 427.86 ± 19 mg/g Total solid(TS) and hydrogen yield of 123.72 mL/g TS were obtained at 200 ℃, increased by 46.41% and 70.79%, respectively. The kinetic parameters from Gompertz model showed torrefaction pretreatment could shorten the lag phase time of enzymatic saccharification and hydrogen production. The reducing sugar data can be fitted well by fractal-like kinetic model and Gompertz model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continuous hydrogen production was conducted in a baffled bioreactor. • HRT and dilution ratio have significant impact on the hydrogen production. • The highest average HPR of 4.63 L/(L·d) was detected in the baffled bioreactor. • Long HRT and high dilution ratio resulted in more electrons in substrate loss. • Dilution can improve the hydrogen from DFEs during photo fermentation. This work studied the sequential hydrogen production by dark and photo-fermentation (HPDPF) in continuous baffled bioreactors. Taken enzymatic hydrolysate of corn stover as initial carbon source, the influence of hydraulic retention time (HRT) of dark fermentation (DF) and the dilution ratio (DR) of dark fermentation effluents (DFEs) on the hydrogen production performance of the combined fermentation system and electron distribution were investigated. For DF unit, the highest hydrogen production rate (HPR) of 5.24 L/(L·d) was detected at HRT of 18 h, however, the maximum HPR of 4.60 L/(L·d) was obtained from DFEs with HRT of 12 h and DR of 1:0.5 during photo fermentation unit, meanwhile, the electrons in substrate partitioning to H 2 reached the maximum value of 35.69%. In terms of hydrogen yield, the optimum operating conditions of the combined system were HRT of 12 h (DF) and DR of 1:0.5(DFEs), in which the hydrogen yield reached 12.73 L/d. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of headspace pressure on photosynthetic hydrogen production was reported. • Reducing the headspace pressure properly could increase hydrogen yield. • The maximum biohydrogen yield of 546.57 mL was obtained at 30 kPa. • Cumulative hydrogen yield of experiments could be fitted well by Gompertz model. In this study, the effect of bioreactor headspace pressure regulation on photo-fermentative hydrogen production (PFHP) from corn stover (CS) was investigated. The results showed that the headspace pressure could significantly affect the performance of PFHP. With the decrease in the reactor headspace pressure (100 kPa–10 kPa), cumulative biohydrogen production first increased and then decreased, the maximum hydrogen yield of 546.57 mL was obtained at the headspace pressure of 30 kPa. The parameters of Gompertz model showed a lower hydrogen partial pressure was beneficial to speed up the reaction process and shorten the hydrogen production delay time of the system, however, too low pressure would inhibit the metabolism of microorganisms in the PFHP process, resulting lower hydrogen yield obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Light absorption range of TiO 2 /ACF broadens from the UV region to the visible region. • Cumulative hydrogen production with TiO 2 /ACF addition was nearly doubled. • The addition of TiO 2 /ACF shortened the photo-fermentation period from 84 h to 48 h. • TiO 2 /ACF promoted metabolic pathway of HAU-M1 to convert acetate and butyrate to H 2. • Characterization results after fermentation confirmed the reusability of TiO 2 /ACF. In this study, titanium dioxide/activated carbon fiber (TiO 2 /ACF) was synthesized by liquid-phase deposition method and the effect of TiO 2 /ACF on the performance of photo-fermentation biohydrogen production (PFHP) from corn stover under visible light catalysis was discussed. Results show the maximum cumulative hydrogen yield (CHY) obtained under the optimal conditions was 74.0 ± 1.3 mL/g TS with TiO 2 /ACF addition of 100 mg/L, which was twice that without TiO 2 /ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO 2 /ACF promoted the metabolic pathway of nitrogenase to reduce H+ produced by consuming acetic acid and butyric acid to hydrogen, and also shortened the photo-fermentation period. By scanning electron microscopy and X-ray diffraction analysis, the morphology and phase structure of TiO 2 /ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO 2 and its practical application in PFHP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin removal rate of CS pretreated with NaOH-heat was as high as 77%. • The highest RS yield of 46.1 g/100 g RM was obtained from 2% NaOH-heat pretreated CS. • 4% NaOH-heat pretreated CS had the minimum HY of 44.27 mL/g TS. • 2% NaOH pretreatment increased the HY of CS by 31.9%. • HPLT of CS was shortened by 58.8% after 2% NaOH pretreatment. The effects of different pretreatment methods, including hydrothermal, acid, alkali, acid-heat and alkali-heat on lignin removal, reducing sugar (RS) yield and photo-fermentative biohydrogen production (PFHP) capability of corn stover (CS) were studied. NaOH-heat pretreatment was the most effective for lignin removal from CS, and the lignin removal rate reached 77%. All the studied pretreatment methods improved the total RS yield of CS, and the highest total RS yield (46.1 g/100 g raw material (RM)) was obtained from 2% NaOH-heat pretreated CS. 2% NaOH pretreatment realized the best PFHP of CS, which increased the hydrogen yield (HY), maximal hydrogen production rate (HPR) and highest hydrogen content (HC) by 31.9%, 50.9% and 20.1% respectively, and shortened hydrogen production lag time (HPLT) by 58.8% over that of untreated CS. However, NaOH-heat and 4% NaOH pretreatment weakened the PFHP capability of CS. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the effects of CaTiO 3 photocatalysts doped with different concentrations of Fe on the biohydrogen production process by photo-fermentation using corn stover as the substrate. The experimental results showed that the maximum cumulative hydrogen production and the maximum rate of hydrogen production were obtained when the doping concentration was 6 % (g/g) (380.8 mL, 26.4 mL/h), which were 63.4 % and 203.4 % higher, respectively, than those of the blank control group (233 mL, 8.7 mL/h). The substrate conversion rate was 32.82 %. Iron-doped CaTiO 3 lowered the oxygen reduction potential in the fermentation system to provide a suitable reduction environment for the growth and fermentation of photosynthetic bacteria. The lowest redox potential observed was −393.5 mV for 6 % iron-doped CaTiO 3. Thermogram analysis revealed a strong correlation between cumulative hydrogen production and redox potential. Additionally, the analysis of soluble small molecules showed that iron-doped CaTiO 3 could inhibit the production of ethanol from glycolysis during fermentation and promote the utilization of small molecule acids. [Display omitted] • Fe-doped CaTiO 3 improves the efficiency of photo fermentative hydrogen production. • The maximum hydrogen production rate increased by 203.4 %. • The maximum cumulative hydrogen production increased by 63.4 %. • Adding Fe-doped CaTiO 3 can inhibit glycolysis to produce ethanol. • Adding Fe-doped CaTiO 3 can improve the reducibility of fermentation broth. [ABSTRACT FROM AUTHOR]

Temperature and pH are key factors that have significant effects on the anaerobic fermentation process. Hence, in this study, a combined bio-hydrogen and bio-methane production process over a range of initial pH and temperature was evaluated. Corn stover was taken as substrate, bio-hydrogen and bio-methane yield, biogas composition and energy conversion efficiency were analyzed. Results showed that the highest hydrogen yield of 69.02 ± 1.75 mL/g VS was obtained with fermentation conditions at initial pH 8 and 35 °C, and the highest methane yield of 249.36 ± 9.81 mL/g VS was obtained from the photofermentation effluent at initial pH 6 and 30 °C. Highest hydrogen and methane contents in the produced biogas were 14.42% and 46.46%, respectively. Furthermore, the highest energy conversion efficiency of 48.83% was obtained with fermentation condition at pH 6 and 30 °C. • Parameter optimization for the two-stage bio-hythane production was studied. • The highest hydrogen yield was observed at initial pH 8 and 35 °C. • The highest methane yield was obtained from effluent at initial pH 6 and 30 °C. • Combination of hydrogen and methane system enhanced energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Rheological properties of substrates significantly affect energy consumption and hydrogen production potential in the process of hydrogen production with stirring. Hence, the rheological properties of corn stover hydrolysate with diverse concentrations and its hydrogen producing capacities under intermittent stirring conditions were investigated in this paper. The results showed that corn stover hydrolysate exhibited pseudo-plastic flow behavior at total solid (TS) of 2.76%–7.65%, and was well fitted by the Power law model. Among four intermittent stirring modes, intermittent stirring C2 (static time: stirring time is 2:1) obtained the highest hydrogen yield of 57.63 ± 1.75 mL g−1 VS, which was 18.97% higher compared with static-culture. Moreover, the maximum hydrogen production rate of intermittent stirring C2 increased by 65.05% compared to continuous stirring. It's a feasible way to improve hydrogen production performance with proper intermittent stirring. • The rheological properties of corn stover hydrolysate were studied. • The Power law model described the flow behavior well. • The bio-hydrogen producing capacity under intermittent stirring were studied. • Proper intermittent stirring mode was identified. [ABSTRACT FROM AUTHOR]

[Display omitted] • Characteristics of four biorefinery methods were compared shoulder by shoulder. • Photo-fermentation biohydrogen production exhibited the greatest economy. • Biomethane presented a maximum yield of 196.0 mL and gross thermal of 6468.4 J/gDM. • Target product of biomethane had the highest CO 2 emissions of 196.01 mL/g DM. Biorefinery technology promotes the realization of the Paris Agreement, China's achievement of its carbon peak, and carbon neutralization. Photo-fermentation biohydrogen production, dark fermentation biohydrogen production, biomethane production, and bioethanol production are several promising biorefinery methods. In this study, corn stover was used as the raw material, and the gas, liquid, and kinetic characteristics of four biorefinery methods were investigated. The production yield, gross thermal energy, economy, and greenhouse gas emissions of the target product per gram of corn stover were studied. The maximum yields of photo-fermentation biohydrogen production, dark fermentation biohydrogen production, biomethane production, and bioethanol production were 68.4 mL/g dry matter (DM), 47.4 mL/g DM, 196.0 mL/g DM, and 2.7 g/L, respectively. The maximum gross thermal energy obtained from biomethane production was 7017.3 J/g DM. The maximum economy of 1.4 RMB/g DM was observed in photo-fermentation biohydrogen production. The highest greenhouse gas emission of the target product from biomethane production was 196.0 mL/g DM. The results provide a reference for the efficient utilization of biomass resources and a comprehensive evaluation of biorefinery technology. [ABSTRACT FROM AUTHOR]

Pilot tests of sequential dark and photo fermentation H 2 production were for the first time conducted in a 11 m 3 reactor (3 m 3 for dark and 8 m 3 for photo compartments). A combined solar and light-emitting diode illumination system and a thermal controlling system was installed and tested. With dark fermentation unit maintained at pH 4.5 and 35 °C and photo fermentation unit at pH 7.0 and 30 °C, the overall biogas production rate using hydrolyzed corn stover as substrate reached 87.8 ± 3.8 m 3 /d with 68% H 2 content, contributed by dark unit at 7.5 m 3 -H 2 /m 3 -d and by photo unit at 4.7 m 3 /m 3 -d. Large variation was noted for H 2 production rate in different compartments of the tested units, revealing the adverse effects of poor mixing, washout, and other inhomogeneity associated with large reactor operations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The best dosage of ascorbic acid to mediate 400 mg/L Fe(0) was 150 mg/L. • Ascorbic acid promoted the Fe(Ⅱ) generation through reduction and chelation. • H 2 produced from ascorbic acid-Fe(0) was 2.7–27.5% higher than Fe(0) at pH 6–9. • Initial pH had an important effect on H 2 production and Fe(0) reactivity. Ascorbic acid was introduced to enhance the performance of zero-valent iron (Fe(0)) in hydrogen production by photo fermentation of bean dregs and corn stover. The highest hydrogen production of 664.0 ± 5.3 mL and hydrogen production rate of 34.6 ± 0.1 mL/h was achieved at 150 mg/L ascorbic acid, which was 10.1% and 11.5% higher than that of 400 mg/L Fe(0) alone. The supplement of ascorbic acid to Fe(0) system accelerated the formation of Fe(Ⅱ) in solution due to its reducing and chelating ability. Hydrogen production of Fe(0) and ascorbic acid-Fe(0) (AA-Fe(0)) systems at different initial pH (5, 6, 7, 8 and 9) was studied. Result showed that hydrogen produced from AA-Fe(0) system was improved by 2.7–27.5% compared with Fe(0) system. The maximum hydrogen production of 767.5 ± 2.8 mL was achieved with initial pH 9 in the AA-Fe(0) system. This study provided a strategy for enhancing biohydrogen production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe0 was first applied to high-load photo fermentation system of corn stover. • Effects of Fe0 sizes (700, 100 and 50 nm) on hydrogen production were compared. • Fe0 buffered pH, stimulated nitrogenase activity and accelerated acid utilization. • Adding 1000 mg/L Fe0-700 obtained the highest hydrogen yield increment of 92.88 %. The aim of this work was to study the effects of Fe0 particle sizes (700 nm, 100 nm and 50 nm) addition on biohydrogen production, liquid culture characteristics and photosynthetic bacterial respond in the high-load photo fermentation system of corn stover within the concentration range of 200–1500 mg/L. Results showed that Fe0 with particle size of 700 nm had a better promotion effect on hydrogen production than 100 nm and 50 nm. The highest hydrogen yield of 74.32 ± 3.48 mL/g TS and hydrogen production rate of 3.31 ± 0.11 mL/g·h TS corn stover were obtained at 1000 and 1500 mg/L Fe0-700 nm, which were significantly increased by 92.88 % and 133.88 % compared with the control group. Further analysis indicated that Fe0 addition effectively alleviated pH drop, enhanced nitrogenase activity, promoted cell growth, and accelerated the consumption of acetic acid and butyric acid. [ABSTRACT FROM AUTHOR]