Biohydrogen production through active saccharification and photo-fermentation from alfalfa

Enhanced the energy conversion of corn stalk via co-production of photo-fermentation biohydrogen and bioethanol

Hydrogen-ethanol co-production can significantly improve the energy conversion efficiency of corn stalk (CS). In this study, with CS as the raw material, the co-production characteristics of one-step and two-step photo-fermentation hydrogen production (PFHP) and ethanol production were investigated. In addition, the gas and liquid characteristics of the experiment were analyzed. The kinetics of hydrogen-ethanol co-production was calculated, and the economics of hydrogen and ethanol were analyzed. Results of the experiments indicated that the two-step hydrogen-ethanol co-production had the best hydrogen production performance when the concentration of CS was 25 g/L. The total hydrogen production was 350.08 mL, and the hydrogen yield was 70.02 mL/g, which was 2.45 times higher than that of the one-step method. The efficiency of hydrogen-ethanol co-production was 17.79 %, which was 2.76 times more efficient than hydrogen compared to fermentation with hydrogen. The result provides technical reference for the high-quality utilization of CS.

Pilot composite tubular bioreactor for outdoor photo-fermentation hydrogen production: From batch to continuous operation

A novel 70 L composite tubular photo-bioreactor was constructed, and its photo-fermentation hydrogen production characteristics of batch and continuous modes were investigated with glucose as the substrate in an outdoor environment. In the batch fermentation stage, the hydrogen production rate peaked at 37.6 mL H2/(L·h) accompanied by a high hydrogen yield of 7 mol H2/mol glucose. The daytime light conversion efficiency is 4 %, with 37 % of light energy from the sun. An optimal hydraulic retention time of 5 d was identified during continuous photo-fermentation. Under this condition, the stability of the cell concentration is maintained and more electrons can be driven to the hydrogen generation pathway while attaining a hydrogen production rate of 20.7 ± 0.9 mL H2/(L·h). The changes of biomass, volatile fatty acids concentration and ion concentration during fermentation were analyzed. Continuous hydrogen production by composite tubular photo-bioreactor offers new ideas for the large-scale deployment of photobiological hydrogen production.

Design of a sustainable system for wastewater treatment and generation of biofuels based on the biomass of the aquatic plant Eichhornia Crassipes

Colombia’s continuous contamination of water resources and the low alternatives to produce biofuels have affected the fulfillment of the objectives of sustainable development, deteriorating the environment and affecting the economic productivity of this country. Due to this reality, projects on environmental and economic sustainability, phytoremediation, and the production of biofuels such as ethanol and hydrogen were combined. The objective of this article was to design and develop a sustainable system for wastewater treatment and the generation of biofuels based on the biomass of the aquatic plant Eichhornia crassipes. A system that simulates an artificial wetland with live E. crassipes plants was designed and developed, removing organic matter contaminants; subsequently, and continuing the sustainability project, bioreactors were designed, adapted, and started up to produce bioethanol and biohydrogen with the hydrolyzed biomass used in the phytoremediation process, generating around 12 g/L of bioethanol and around 81 ml H2/g. The proposed research strategy suggests combining two sustainable methods, bioremediation and biofuel production, to preserve the natural beauty of water systems and their surroundings.

Design of a sustainable system for wastewater treatment and generation of biofuels based on the biomass of the aquatic plant Eichhornia Crassipes

Colombia's continuous contamination of water resources and the low alternatives to produce biofuels have affected the fulfillment of the objectives of sustainable development, deteriorating the environment and affecting the economic productivity of this country. Due to this reality, projects on environmental and economic sustainability, phytoremediation, and the production of biofuels such as ethanol and hydrogen were combined. The objective of this article was to design and develop a sustainable system for wastewater treatment and the generation of biofuels based on the biomass of the aquatic plant Eichhornia crassipes. A system that simulates an artificial wetland with live E. crassipes plants was designed and developed, removing organic matter contaminants; subsequently, and continuing the sustainability project, bioreactors were designed, adapted, and started up to produce bioethanol and biohydrogen with the hydrolyzed biomass used in the phytoremediation process, generating around 12 g/L of bioethanol and around 81 ml H2/g. The proposed research strategy suggests combining two sustainable methods, bioremediation and biofuel production, to preserve the natural beauty of water systems and their surroundings.

Enhancement of biohydrogen production by photo-fermentation of corn stover via visible light catalyzed titanium dioxide/activated carbon fiber

In this study, titanium dioxide/activated carbon fiber (TiO2/ACF) was synthesized by liquid-phase deposition method and the effect of TiO2/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 TiO2/ACF addition of 100 mg/L, which was twice that without TiO2/ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO2/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 TiO2/ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO2 and its practical application in PFHP.

The Design of a Sustainable Industrial Wastewater Treatment System and The Generation of Biohydrogen from E. crassipes

Water scarcity is a significant global issue caused by the prolonged disregard and unsustainable management of this essential resource by both public and private bodies. The dependence on fossil fuels further exacerbates society's bleak environmental conditions. Therefore, it is crucial to explore alternative solutions to preserve our nation's water resources properly and promote the production of biofuels. Research into the utilization of E. crassipes to remove heavy metals and generate biofuels is extensive. The combination of these two lines of inquiry presents an excellent opportunity to achieve sustainable development goals. This study aims to develop a sustainable wastewater treatment system and generate biohydrogen from dry, pulverized E. crassipes biomass. A treatment system was implemented to treat 1 L of industrial waste. The interconnected compartment system was built by utilizing recycled PET bottles to generate biohydrogen by reusing the feedstock for the treatment process. The production of biological hydrogen through dark fermentation, using biomass containing heavy metals as a biohydrogen source, was studied. Cr (VI) and Pb (II) levels had a low impact on hydrogen production. The uncontaminated biomass of E. crassipes displayed a significantly higher hydrogen yield (81.7 mL H2/g glucose). The presence of Cr (IV) in E. crassipes leads to a decrease in biohydrogen yield by 14%, and the presence of Pb (II) in E. crassipes leads to a decrease in biohydrogen yield of 26%. This work proposes a strategy that utilizes green technologies to recover and utilize contaminated water. Additionally, it enables the production of bioenergy with high efficiency, indirectly reducing greenhouse gases. This strategy aligns with international programs for the development of a circular economy.

Effect of deep eutectic solvent pretreatment on biohydrogen production from corncob: pretreatment temperature and duration

Deep eutectic solvent pretreatment with different temperatures and durations was applied to corncob to increase hydrogen yield via photo-fermentation. The correlation of composition, enzymatic hydrolysis, and hydrogen production in pretreated corncobs, as well as energy conversion was evaluated. Deep eutectic solvent pretreatment effectively dissolved lignin, retained cellulose, and enhanced both enzymatic hydrolysis and hydrogen production. The maximum cumulative hydrogen yield obtained under a pretreatment condition of 50°C and 12 h was 677.45 mL; this was 2.72 times higher than that of untreated corncob, and the corresponding lignin removal and enzymatic reduction of sugar concentration were 79.15% and 49.83 g/L, respectively; the highest energy conversion efficiency was 12.08%. The hydrogen production delay period was shortened, and the maximum shortening time was 18.9 h. Moreover, the cellulose content in pretreated corncob was positively correlated with both reducing sugar concentration and hydrogen yield and had the strongest influence on hydrogen production.

Enhancement on photobiological hydrogen production from corn stalk via reducing hydrogen pressure in bioreactors by way of phased decompression schemes

In this project, it was verified that properly reducing the bioreactor hydrogen partial pressure (HPP) could significantly enhance the photo-fermentative hydrogen production (PFHP) by corn stalk. The maximal cumulative hydrogen yield (CHY) of 82.37 mL/g was obtained under full decompression to 0.4 bar, which was 35% higher than that without decompression. To increase CHY and save the pressure control cost, 12-hour, 24-hour and 36-hour decompression schemes were provided, and the optimal decompression phase in fermentation under each scheme was investigated. The 12-hour decompression scheme was suitable for 24-36 h of fermentation; the 24-hour decompression scheme implemented within 12-36 h of fermentation had a more desirable CHY; when adopting the 36-hour decompression scheme, operation during 12-48 h yielded a CHY of 81.70 mL/g that approximated whole process decompression. The strategies of decompression at the appropriate phase of fermentation were innovative, which offered a new option for optimizing PFHP economically.

Enhanced biohydrogen yield and light conversion efficiency during photo-fermentation using immobilized photo-catalytic nano-particles

Bacterial immobilization is a common method in anaerobic fermentation, since of the maintenance of high bacterial activity, insurance of high density microbial during continuous fermentation, and quick adaptability to the environment. While, the bio-hydrogen production capacity of immobilized photosynthetic bacteria (I-PSB) is seriously affected by the low light transfer efficiency. Hence, in this study, photo-catalytic nano-particles (PNPs) was added into the photo-fermentative bio-hydrogen production (PFHP) system, and its enhancement effects of bio-hydrogen production performance were investigated. Results showed that the maximum cumulative hydrogen yield (CHY) of I-PSB with 100 mg/L nano-SnO₂ (154.33 ± 7.33 mL) addition was 18.54% and 33.06% higher than those of I-PSB without nano-SnO₂ addition and control group (free cells), and the lag time was the shortest indicating a shorter cell arrest time, more cells and faster response. Maximum energy recovery efficiency and light conversion efficiency were also found to be increased by 18.5% and 12.4%, respectively.

Enhancing biohydrogen yield from corn stover by photo fermentation via adjusting photobioreactor headspace pressure

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 firstincreased 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.

Deep eutectic solvent with Lewis acid for highly efficient biohydrogen production from corn straw

To boost saccharification and biohydrogen production efficiency from corn straw, Lewis acid enhanced deep eutectic solvent (DES) pretreatment using choline chloride/glycerol was developed. A notable enhancement of the enzymatic hydrolysis efficiency from 26.3 % to 87.0 % was acquired when corn straw was pretreated with aqueous DES at 100 °C for 5 h using 2.0 wt% AlCl₃. A maximum biohydrogen yield of 114.8 mL/g total solids (TS) was achieved in the sequential dark fermentation stage, which was 2.1 times higher than that of the raw feedstock (37.1 mL/g TS). The enhanced efficient conversion was ascribed to the effective removal of lignin and hemicellulose, which led to the bio-accessibility of the straw. This work provides new sights for the rational design of efficient AlCl₃-aided aqueous DES system toward biohydrogen production from lignocellulosic biomass.

Enhancing biohydrogen production from lignocellulosic biomass of Paulownia waste by charge facilitation in Zn doped SnO2 nanocatalysts

The goal of this research was to study the role of excess charges in regulating biohydrogen production from Paulownia. The excess charges were generated through charge compensation in SnO₂ nanocatalysts by Zn doping. The maximum hydrogen yield of 335 mL was observed at 8%Zn doping with a concentration of 150 mg/L, 47% higher as compared to standard sample. It was observed that the hydrogen production rate increased with Zn doping and the highest value (77 mL/h) was observed for 8%Zn at 24 h. The decrease in the total amount of byproducts (2.52 g/L from 4.28 g/L) at 8% Zn indicates an increase in bacterial metabolism. The lowest value of oxidation-reduction potential (-525 mV) at 24 h for 8%Zn confirms that Zn doping provides excessive electrons to the fermentative medium which helps the bacteria to transfer electrons faster during the redox reaction, hence, enhancing the enzymatic process and eventually hydrogen production.

Effect of citrate buffer on hydrogen production by photosynthetic bacteria

The effect of citrate buffer on biohydrogen production using photosynthetic bacteria was studied. The study was performed in two steps. First, specific concentrations of citrate and sodium citrate as buffers were mixed into batch cultures, and the effects of these buffers on fermentation broth characteristics and biohydrogen production were analyzed. The maximum overall biohydrogen yield of 411.4 mL, which was 42% higher to the control group, was obtained with 0.05 mol/L citrate buffer. Then, the effect of 0.05 mol/L citrate buffer on biohydrogen yield at different pH values (5.5-7.5) were explored. The maximum biohydrogen yield of 429.82 mL was obtained at pH 6, and the final pH values were effectively controlled. The findings indicated that citrate buffer seriously affected the pH of the reaction liquid. The results provide technical support to stabilize the pH of photo-fermentation broth and improve biohydrogen production performance.

Enhancing photo-fermentation biohydrogen production from corn stalk by iron ion

This study aimed to investigate the enhancement of iron ion on growth, metabolic pathway, and biohydrogen production performance of biohydrogen producing bacteria HAU-M1. Different concentrations of Fe²⁺ and Fe³⁺ were respectively added into fermentation broth of photo-fermentation biohydrogen production (PFHP) from corn stalk. Regular sampling test was used to measure the characteristics of fermentation broth and gas, metabolic pathway, energy conversion efficiency, and kinetic of PFHP. The analysis of experimental data showed that the maximum hydrogen yield of 70.25 mL/g was observed at 2500 μmol/L Fe²⁺ addition, with an energy conversion efficiency of 5.21%, which was 19.98% higher over no-addition. However, the maximum hydrogen content of 51.41% and the maximum hydrogen production rate of 17.82 mL/h were observed at 2000 μmol/L Fe²⁺ addition. The experimental results revealed that iron ion played a key role in PFHP, which provided a technical support for improving the performance of PFHP.

Enhancing photo-fermentative biohydrogen production using different zinc salt additives

The kinetic properties of the hydrogen yield of photosynthetic bacteria were investigated using Han-Levenspiel and modified Gompertz models to determine the effects of different zinc salts on the growth and hydrogen production of the photosynthetic bacterium HAU-M1. Inorganic zinc salts (zinc standard solution and zinc sulfate) inhibited bacterial growth by 1-4-fold higher than organic zinc salts (zinc lactate and zinc gluconate). Among these four zinc salts, 5 mg/L zinc lactate displayed the weakest inhibition performance. This compound increased cumulative hydrogen production by approximately 57.81% (80.44 mL/g) and maximum hydrogen production rate by 58.27% (3.43 mL/[g·h]). The Han-Levenspiel model with parameters m > n > 0 indicated that the addition of zinc salts influenced the hydrogen production process of the bacterium in a noncompetitive manner. Compared with the inorganic zinc, the organic zinc salts were more suitable as exogenous zinc supplements to promote bacterial growth and its hydrogen production.

Analysis of the characteristics of paulownia lignocellulose and hydrogen production potential via photo fermentation

Paulownia biomass is rich in carbohydrates, making which a potential feedstock for biohydrogen production. In the study, different parts and varieties of Paulownia were chose as substrates to evaluate hydrogen production potential of paulownia lignocellulose via biohydrogen production by photo fermentation (BHPPF) and energy conversion efficiency (ECE). Results showed the highest cumulative hydrogen yield (CHY) of 67.11 mL/g total solids (TS) and ECE of 4.74% were obtained from leaves of Paulownia, which were 121.06% and 115.45% higher than those of the branches. Moreover, Paulownia jianshiensis leaves were found to be the best variety for BHPPF, with the maximum CHY of 98.83 mL/g TS and ECE of 7.18%. Using Paulownia waste as the substrate to produce hydrogen helps broaden the range of raw materials for BHPPF and improve the economic utilization of forestry waste.

Extraction optimization and quality evaluation of humic acids from lignite using the cell-free filtrate of Penicillium ortum MJ51

Bio-solubilization of lignite is a promising technology to transform coal into humic acids (HAs) which are broadly used in agriculture. In this work, HAs were extracted from lignite using the cell-free filtrate (CFF) of Penicillium ortum MJ51. The extraction method was optimized using response surface methodology (RSM) based on the interactive effects of nitric acid concentrations, coal loading ratio, extraction temperature and time as input factors, and the absorbance of HAs at 450 nm wavelength as the output response. Under optimized conditions (lignite pretreated with 4.7 N HNO₃, coal loading ratio of 4.9%, temperature of 77.3 °C and time of 8.6 hours), the absorbance at 450 nm peaked at 70.28, and the concentration and extraction yield of HAs were 31.3 g L⁻¹ and 63.9%, respectively, which were dramatically higher than those observed for traditional biological methods (0.7 g L⁻¹ and 14.1%, respectively). The qualities of HAs produced under optimized conditions were evaluated and compared with those extracted by the conventional chemical method. The optimized process resulted in better HA quality indices, including lower molecular mass; higher nitrogen; less aromatic carbon; more aliphatic and carboxylic carbon; and higher bioactivity for promoting plant growth. Moreover, the anti-flocculation ability was improved, thereby supporting its applicability in agriculture. Extraction of HAs from lignite using the CFF of P. ortum MJ51 provides a novel technological approach for the efficient conversion of lignite to bio-active HAs.

Bio-solubilization of lignite is a promising technology to transform coal into humic acids (HAs) which are broadly used in agriculture.

Study of the interrelationship between nano-TiO2 addition and photo-fermentative bio-hydrogen production of corn straw

This study explored the interrelationship between nano-TiO₂ addition and photo-fermentative hydrogen production (PFHP) of corn straw. The maximum cumulative hydrogen volume (CHV) was up to 688.8 mL under the optimal photo-fermentative process conditions with nano-TiO₂ addition of 300 mg/L. Initial pH and interaction between substrate concentration and light intensity had highly significant effects on PFHP of corn straw with nano-TiO₂ addition. With the improvement of CHV, nano-TiO₂ addition decreased the optimal initial pH and substrate concentration for PFHP of corn straw. Moreover, nano-TiO₂ addition promoted the metabolism of butyric acid and acetic acid by photosynthetic bacteria HAU-M1, and significantly reduced the total concentration of intermediate byproducts during hydrogen production to a low level of 1.6-2.5 g/L, thus making the CHV, maximum hydrogen production rate (HPR) and average hydrogen content (HC) increased by 32.6%, 27.9% and 8.3% respectively over the control without nano-TiO₂ addition.

Enhanced biohydrogen production from corn straw by basalt fiber addition

The aim of this work was to study the impact of basalt fiber (BF) on hydrogen fermentation of corn straw. The maximum of hydrogen yield and corn straw conversion rate respectively achieved 323.94 mL and 5.23% by adding 1.5 g/L BF particle with the size of 300-400 mesh, which increased by 15.74% and 15.6% respectively than control group. The BF could promote the growth of photosynthetic bacteria, subsequently influencing the products distribution and hydrogen generation. Overall, this investigation demonstrated that BF addition is an effective way to enhance biohydrogen production from corn straw.

Recycling of shrub landscaping waste: Exploration of bio-hydrogen production potential and optimization of photo-fermentation bio-hydrogen production process

Shrub landscaping waste, derived from afforestation of city, has increased annually, making it a promising feedstock for energy production. In this work, the photo-fermentation bio-hydrogen production potential from shrub landscaping waste was evaluated. Eight kinds of shrub landscaping wastes (Photinia fraseri, Buxus megistophylla, Buxus sinica, Pittosporum tobira, Sabina Chinensis, Berberis thunbergii, Ligustrum vicaryi and Ligustrum quihoui) were selected as substrate and the photo-fermentation bio-hydrogen production process of which was optimized. Buxus megistophylla was found to be the most suitable substrate for photo-fermentation bio-hydrogen production. Moreover, the initial pH value, temperature and substrate concentration had significant influence on photo-fermentation bio-hydrogen production. The maximum cumulated hydrogen yield of Buxus megistophylla was 73.82 ± 0.06 mL/g TS under the optimal conditions of light intensity of 3000 Lux, substrate mass concentration of 21.49 g/L, temperature of 29.78 °C, inoculant amount of 25% and initial pH value of 6.78.

Main Hydrogen Production Processes: An Overview

Due to its characteristics, hydrogen is considered the energy carrier of the future. Its use as a fuel generates reduced pollution, as if burned it almost exclusively produces water vapor. Hydrogen can be produced from numerous sources, both of fossil and renewable origin, and with as many production processes, which can use renewable or non-renewable energy sources. To achieve carbon neutrality, the sources must necessarily be renewable, and the production processes themselves must use renewable energy sources. In this review article the main characteristics of the most used hydrogen production methods are summarized, mainly focusing on renewable feedstocks, furthermore a series of relevant articles published in the last year, are reviewed. The production methods are grouped according to the type of energy they use; and at the end of each section the strengths and limitations of the processes are highlighted. The conclusions compare the main characteristics of the production processes studied and contextualize their possible use.

Photo-biological hydrogen production by a temperature-tolerant mutant of Rhodobacter capsulatus isolated by transposon mutagenesis

Screening of high temperature tolerant strains is important for photo-fermentative hydrogen production in natural conditions which exhibit wide temperature variations. Hence, a temperature-tolerant strain of Rhodobacter capsulatus was isolated by transposon mutagenesis. The mutant strain Rhodobacter capsulatus MX01 could convert cornstalk hydrolysate into hydrogen successfully, and exhibited better hydrogen production performance at higher culture temperature (33 °C and 37 °C) and light intensity (5000 lx and 7000 lx) than the wild type strain. At 33 °C and 5000 lx, the total hydrogen production yield and rate of MX01 from cornstalk hydrolysate were 3.64 ± 0.18 mol-H₂/g-cornstalk and 40.07 ± 1.70 mmol-H₂/(h·g-cornstalk), respectively. The energy conversion efficiency of cornstalk hydrolysate to hydrogen for the mutant strain MX01 was 10.6%. This higher temperature- and light intensity-tolerant mutant MX01 could carry out photo-fermentation at outdoor settings, which is important for eco-friendly, low-cost and energy-saving practical application of bio-hydrogen production.

Enhancement of the biohydrogen production performance from mixed substrate by photo-fermentation: Effects of initial pH and inoculation volume ratio

Co-digestion of substrates can improve hydrogen yield (HY) by adjusting carbon nitrogen ratio (C/N) of fermentation substrates. This study evaluated the enhancement of hydrogen production from co-digestion of duckweed and corn straw via photo-fermentation. The maximum HY of 78.0 mL/g Total solid (TS) was obtained from the mixed ratio of 5:1 (C/N of 13.2), which was 25.4% and 29.6% higher than those of single substrate of duckweed and corn straw, respectively. The effects of initial pH and inoculation volume ratio (IVR) on co-digestion photo-fermentative hydrogen production (CD-PFHP) from duckweed and corn straw were further studied. A maximum HY of 85.6 mL/g TS was achieved under the optimal condition (initial pH 8, IVR 20%, mix ratio of duckweed and corn straw of 5:1). Additionally, both mix ratio and initial pH showed statistical difference (p < 0.05). Acetic acid and butyric acid were found to be the main metabolic by-products during CD-PFHP.

Enhancement of pH values stability and photo-fermentation biohydrogen production by phosphate buffer

The main aim of this study was to investigate the effects of the initial pH values of the buffer on photo-fermentation biohydrogen production. Hydrogen production and the kinetics of it under different initial pH values were analyzed. Effects of initial pH values on reducing sugar consumption, hydrogen production rate, and byproduct production were evaluated at initial pH values of 5–7. The results showed that initial pH values of phosphate buffer had a significant effect on biohydrogen production via photo-fermentation. With the initial pH value of phosphate buffer at 6.0, the cumulative hydrogen production reached its maximum, 569.6 mL. The maximum hydrogen production rate was 23.96 mL/h at the initial pH value of 6.5. With the initial pH values at 5.0 and 7.5, the maximum hydrogen production rates were becoming lower, only 5.59 mL/h and 5.42 mL/h, respectively. And with the increase in pH values, the peak period of hydrogen production was gradually delayed, indicating that the alkaline environment had a negative effect on the ability of photosynthetic bacteria. This study revealed the influence of phosphate buffer initial pH values on the biohydrogen production via photo-fermentation and aimed to provide a scientific reference for further improving the theory and technology for biohydrogen production from biomass.

Comparative analysis of prediction models for methane potential based on spent edible fungus substrate

In this study, ten spent edible fungus (SEF) with different compositional features were used for the maximum methanogenic potential (P₀) evaluation, and the prediction models including regression and kinetics based on this were developed separately. The results showed that the regression model with more chemical components had a good correlation with the P₀, and at least three chemical compositions could reach the threshold of sensitivity. The Cone model showed the best fitting effect on P₀ in all kinetic models, which had higher R-square (>0.994) and lower error (1.004-5.672%). Meanwhile, the minimum digestive testing time (14 days) was determined by the evaluation of sensitivity via statistical indicators. It is concluded that the determination of the prediction model of P₀ should be evaluated with the combination of statistical indicators and specific requirements.

Enhanced buffer capacity of fermentation broth and biohydrogen production from corn stalk with Na2HPO4/NaH2PO4

The remarkable buffer capacity of buffer solution can significantly improve the biohydrogen production yield and energy conversion efficiency. In the present study, the effect of buffer solution Na₂HPO₄/NaH₂PO₄ on buffer capacity of fermentation broth and photo-fermentation biohydrogen production (PFHP) was studied. Gas characteristics, fermentation broth properties, and kinetic parameters in PFHP were investigated. With the increase in pH values (5-7) of buffer solution Na₂HPO₄/NaH₂PO₄, firstly hydrogen yield increased and then decreased. Maximum energy conversion efficiency 9.84%, hydrogen yield 132.69 mL/g corn stalk, and hydrogen content 53.88% were achieved at pH value of 6. The results of one-way ANOVA showed that pH values of fermentation broth and cumulative hydrogen production were strongly affected by pH values of buffer solution. Buffer solution Na₂HPO₄/NaH₂PO₄ retarded the decrease of pH value of photo-fermentation broth, and significantly improved the PFHP.