Enhancing bio-hydrogen and bio-methane production of concentrated latex wastewater (CLW) by Co-digesting with palm oil mill effluent (POME): Batch and continuous performance test and ADM-1 modeling.

This study aimed at investigating the biohydrogen and biomethane potential of co-digestion from palm oil mill effluent (POME) and concentrated latex wastewater (CLW) in a two-stage anaerobic digestion (AD) process under thermophilic (55 ± 3 °C) and at an ambient temperature (30 ± 3 °C) conditions, respectively. The batch experiments of POME:CLW mixing ratios of 100:0, 70:30, 50:50, 30:70, and 0:100 was investigated with the initial loadings at 10 g-VS/L. The highest hydrogen yield of 115.57 mLH2/g-VS was obtained from the POME: CLW mixing ratio of 100:0 with 29.0 of C/N ratio. While, the highest subsequent methane production yield of 558.01 mLCH4/g-VS was achieved from hydrogen effluent from POME:CLW mixing ratio of 70:30 0 with 21.8 of C/N ratio. This mixing ratio revealed the highest synergisms of about 9.21% and received maximum total energy of 19.70 kJ/g-VS. Additionally, continuous hydrogen and methane production were subsequently performed in a series of continuous stirred tank reactor (CSTR) and up-flow anaerobic sludge blanket reactor (UASB) to treat the co-substate. The results indicated that the highest hydrogen yield of POME:CLW mixing ratio at 70:30 of 95.45 mL-H2/g-VS was generated at 7-day HRT, while methane production was obtained from HRT 15 days with a yield of 204.52 mL-CH4/g-VS. Thus, the study indicated that biogas production yield of CLW could be enhanced by co-digesting with POME. In addition, the two-stage AD model under anaerobic digestion model no. 1 (ADM-1) framework was established, 9.10% and 2.43% of error fitting of hydrogen and methane gas between model simulation data and experimental data were found. Hence, this research work presents a novel approach for optimization and feasibility for co-digestion of POME with CLW to generate mixed gaseous biofuel potentially.

Influence of Nanomaterials and Other Factors on Biohydrogen Production Rates in Microbial Electrolysis Cells-A Review.

Microbial Electrolysis Cells (MECs) are one of the bioreactors that have been used to produce bio-hydrogen by biological methods. The objective of this comprehensive review is to study the effects of MEC configuration (single-chamber and double-chamber), electrode materials (anode and cathode), substrates (sodium acetate, glucose, glycerol, domestic wastewater and industrial wastewater), pH, temperature, applied voltage and nanomaterials at maximum bio-hydrogen production rates (Bio-HPR). The obtained results were summarized based on the use of nanomaterials as electrodes, substrates, pH, temperature, applied voltage, Bio-HPR, columbic efficiency (CE) and cathode bio-hydrogen recovery (C Bio-HR). At the end of this review, future challenges for improving bio-hydrogen production in the MEC are also discussed.

3D reconstruction and morphological analysis of electrostimulated hyperthermophile biofilms of Thermotoga neapolitana.

In this study, the morphological characteristics of the T. neapolitana biofilms on a ceramic carrier, stainless steel, graphite foil, carbon paper, carbon felt and carbon cloth using 3D reconstruction technology was investigated. This was based on the micrographs available in Squadrito et al. (Data Brief 33: 106-403, 2020). Besides the ceramic carrier, the other surfaces were conductive and slightly positively polarised (0.8 and 1.2 V). A simple drying technique was used to show the biofilm and avoid its detachment while chemical fixing with glutaraldehyde was used to better highlight the bacterial morphology within the biofilm. The latter was more suitable for investigating biofilm morphology while the former for bacteria morphology. For the ceramic carrier and stainless steel electrode surfaces, a regular undulating pattern of the biofilm was highlighted by the 3D rendering whilst the glutaraldehyde fixed sample showed a rod-like bacteria morphology. For the other surfaces, a regular undulating pattern of the biofilm and a mixture of a rod-like and a coccoid form of settled bacteria were evidenced also. Carbon cloth was the more suitable electrode for the current application due to its richer filamentous network of bacteria biofilm suggesting a better prevention of bacteria detachment from the electrode surface. Indeed, a preserved biofilm was highlighted on the surfaces of the polarised carbon cloth.

Hydrogen production automatic control in continuous microbial electrolysis cells reactors used in wastewater treatment.

In this paper, two control laws are proposed and applied in a model for a continuous Microbial Electrochemical Cells system. The used model is based on mass balances describing the behavior of substrate consumption, microbial growth, competition between anodophilic and methanogenic microorganisms for the carbon source in the anode, hydrogen generation, and electrical current production. The main control objective is to improve the electrical current generated and thus the production of bio-hydrogen gas in the reactor, using the dilution rate and the applied potential as individual control input variables. The control laws implemented are nonlinear adaptive type. In order to demonstrate its usefulness, numerical simulation runs involving multiple set-point changes and input perturbations were conducted for each control variable. The results of these simulations show that both control laws were able to respond adequately and efficiently to the disturbances and reach the reference value to which they were subjected. Moreover, it is possible to control both the electrical current produced and the hydrogen produced. Finally, these simulations also show that the highest rate of hydrogen production can be obtained using the applied potential as a control input, but such productivity is only attainable for a short period of time.

Expanding the substrates for a bacterial hydrogenlyase reaction.

Escherichia coli produces enzymes dedicated to hydrogen metabolism under anaerobic conditions. In particular, a formate hydrogenlyase (FHL) enzyme is responsible for the majority of hydrogen gas produced under fermentative conditions. FHL comprises a formate dehydrogenase (encoded by fdhF) linked directly to [NiFe]-hydrogenase-3 (Hyd-3), and formate is the only natural substrate known for proton reduction by this hydrogenase. In this work, the possibility of engineering an alternative electron donor for hydrogen production has been explored. Rational design and genetic engineering led to the construction of a fusion between Thermotoga maritima ferredoxin (Fd) and Hyd-3. The Fd-Hyd-3 fusion was found to evolve hydrogen when co-produced with T. maritima pyruvate :: ferredoxin oxidoreductase (PFOR), which links pyruvate oxidation to the reduction of ferredoxin. Analysis of the key organic acids produced during fermentation suggested that the PFOR/Fd-Hyd-3 fusion system successfully diverted pyruvate onto a new pathway towards hydrogen production.

Inoculum pre-treatment affects the fermentative activity of hydrogen-producing communities in the presence of 5-hydroxymethylfurfural.

To enhance the productivity of mixed microbial cultures for fermentative bio-hydrogen production, chemical-physical pre-treatments of the original seed are needed to suppress the activity of hydrogen (H2)-consuming microbes. This approach might influence negatively the composition and diversity of the hydrogen-producing community with consequences on the functional stability of the H2-producing systems in case of perturbations. In this study, we aimed at investigating the effect of different types of pre-treatment on the performance of hydrogen production systems in the presence of an inhibitor, such as 5-hydroxymethylfurfural (HMF). The efficiency and the microbial community structure of batch reactors amended with HMF and inoculated with non-pretreated and pretreated (acid, heat shock, and aeration) anaerobic sludge were evaluated and compared with control systems. The type of pre-treatments influenced the microbial community assembly and activity in inhibited systems, with significant effect on the performance. Cumulative H2 production tests showed that the pre-aerated systems (control and HMF inhibited) were the most efficient, while the difference of the lag phase of the pre-acidified control and HMF-added test was negligible. Analyses of the structure of the enriched microbial community in the systems through PCR-denaturing gradient gel electrophoresis (DGGE) followed by band sequencing revealed that the differences in performance were mostly related to shifts in the metabolic pathways rather than in the predominant species. In conclusion, the findings suggest that the use of specific inoculum pre-treatment could contribute to regulate the metabolic activity of the fermentative H2-producing bacteria in order to enhance the bio-energy production.

Critical analysis of hydrogen production from mixed culture fermentation under thermophilic condition (60 °C).

Bio-hydrogen production from mixed culture fermentation (MCF) of glucose was studied by conducting a comprehensive product measurement and detailed mass balance analysis of their contributions to the final H2 yield. The culture used in this study was enriched on glucose at 60 °C through a sequential batch operation consisting of daily glucose feeds, headspace purging and medium replacement every third day in serum bottles for over 2 years. 2-Bromoethanesulfonate (BES) was only required during the first three 3-day cycles to permanently eliminate methanogenic activity. Daily glucose feeds were fully consumed within 24 h, with a persistent H2 yield of 2.7 ± 0.1 mol H2/mol glucose, even when H2 was allowed to accumulate over the 3-day cycle. The measured H2 production exceeded by 14 % the theoretical production of H2 associated with the fermentation products, dominated by acetate and butyrate. Follow-up experiments using acetate with a (13)C-labelled methyl group showed that the excess H2 production was not due to acetate oxidation. Chemical formula analysis of the biomass showed a more reduced form of C5H11.8O2.1N1.1 suggesting that the biomass formation may even consume produced H2 from fermentation.

Isolation and characterization of a new [FeFe]-hydrogenase from Clostridium perfringens.

This paper reports the first characterization of an [FeFe]-hydrogenase from a Clostridium perfringens strain previously isolated in our laboratory from a pilot-scale bio-hydrogen plant that efficiently produces H2 from waste biomasses. On the basis of sequence analysis, the enzyme is a monomer formed by four domains hosting various iron-sulfur centres involved in electron transfer and the catalytic center H-cluster. After recombinant expression in Escherichia coli, the purified protein catalyzes H2 evolution at high rate of 1645 ± 16 s(-1) . The optimal conditions for catalysis are in the pH range 6.5-8.0 and at the temperature of 50 °C. EPR spectroscopy showed that the H-cluster of the oxidized enzyme displays a spectrum coherent with the Hox state, whereas the CO-inhibited enzyme has a spectrum coherent with the Hox -CO state. FTIR spectroscopy showed that the purified enzyme is composed of a mixture of redox states, with a prevalence of the Hox ; upon reduction with H2 , vibrational modes assigned to the Hred state were more abundant, whereas binding of exogenous CO resulted in a spectrum assigned to the Hox -CO state. The spectroscopic features observed are similar to those of the [FeFe]-hydrogenases class, but relevant differences were observed given the different protein environment hosting the H-cluster.

Advances in the biotechnology of hydrogen production with the microalga Chlamydomonas reinhardtii.

Biological hydrogen production is being evaluated for use as a fuel, since it is a promising substitute for carbonaceous fuels owing to its high conversion efficiency and high specific energy content. The basic advantages of biological hydrogen production over other "green" energy sources are that it does not compete for agricultural land use, and it does not pollute, as water is the only by-product of the combustion. These characteristics make hydrogen a suitable fuel for the future. Among several biotechnological approaches, photobiological hydrogen production carried out by green microalgae has been intensively investigated in recent years. A select group of photosynthetic organisms has evolved the ability to harness light energy to drive hydrogen gas production from water. Of these, the microalga Chlamydomonas reinhardtii is considered one of the most promising eukaryotic H2 producers. In this model microorganism, light energy, H2O and H2 are linked by two excellent catalysts, the photosystem 2 (PSII) and the [FeFe]-hydrogenase, in a pathway usually referred to as direct biophotolysis. This review summarizes the main advances made over the past decade as an outcome of the discovery of the sulfur-deprivation process. Both the scientific and technical barriers that need to be overcome before H2 photoproduction can be scaled up to an industrial level are examined. Actual and theoretical limits of the efficiency of the process are also discussed. Particular emphasis is placed on algal biohydrogen production outdoors, and guidelines for an optimal photobioreactor design are suggested.

Mesophilic hydrogen production in acidogenic packed-bed reactors (APBR) using raw sugarcane vinasse as substrate: Influence of support materials.

Bio-hydrogen production from sugarcane vinasse in anaerobic up-flow packed-bed reactors (APBR) was evaluated. Four types of support materials, expanded clay (EC), charcoal (Ch), porous ceramic (PC), and low-density polyethylene (LDP) were tested as support for biomass attachment. APBR (working volume - 2.3 L) were operated in parallel at a hydraulic retention time of 24 h, an organic loading rate of 36.2 kg-COD m(-3) d(-1), at 25 °C. Maximum volumetric hydrogen production values of 509.5, 404, 81.4 and 10.3 mL-H2 d(-1) L(-1)reactor and maximum yields of 3.2, 2.6, 0.4 and 0.05 mol-H2 mol(-1) carbohydrates total, were observed during the monitoring of the reactors filled with LDP, EC, Ch and PC, respectively. Thus, indicating the strong influence of the support material on H2 production. LDP was the most appropriate material for hydrogen production among the materials evaluated. 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and scanning electron microscopy confirmed the selection of different microbial populations. 454-pyrosequencing performed on samples from APBR filled with LDP revealed the presence of hydrogen-producing organisms (Clostridium and Pectinatus), lactic acid bacteria and non-fermentative organisms.

Treatment of industrial wastewaters by algae-bacterial consortium with Bio-H2 production: Recent updates, challenges and future prospects.

Currently, scarcity/security of clean water and energy resources are the most serious problems worldwide. Industries use large volume of ground water and a variety of chemicals to manufacture the products and discharge large volume of wastewater into environment, which causes severe impacts on environment and public health. Fossil fuels are considered as major energy resources for electricity and transportation sectors, which release large amount of CO2 and micro/macro pollutants, leading to cause the global warming and public health hazards. Therefore, algae-bacterial consortium (A-BC) may be eco-friendly, cost-effective and sustainable alternative way to treat the industrial wastewaters (IWWs) with Bio-H2 production. A-BC has potential to reduce the global warming and eutrophication. It also protects environment and public health as it converts toxic IWWs into non or less toxic (biomass). It also reduces 94%, 90% and 50% input costs of nutrients, freshwater and energy, respectively during IWWs treatment and Bio-H2 production. Most importantly, it produce sustainable alternative (Bio-H2) to replace use of fossil fuels and fill the world's energy demand in eco-friendly manner. Thus, this review paper provides a detailed knowledge on industrial wastewaters, their pollutants and toxic effects on water/soil/plant/humans and animals. It also provides an overview on A-BC, IWWs treatment, Bio-H2 production, fermentation process and its enhancement methods. Further, various molecular and analytical techniques are also discussed to characterize the A-BC structure, interactions, metabolites and Bio-H2 yield. The significance of A-BC, recent update, challenges and future prospects are also discussed.

A review on biological biohydrogen production: Outlook on genetic strain enhancements, reactor model and techno-economics analysis.

Modernisation of industrial and transportation sector would have not imaginable without the help of fossil fuels, but constant usage has led to many environmental concerns. As a step forward, for safer next generation living we are forced to look into green fuels like bio­hydrogen and higher alcohols. This review mainly focuses on bio­hydrogen production via biological pathways, genetic improvements, knowledge gap, economics, and future directions. Dark and photo fermentation process with the factor influence the process (pH regulation, temperature, hydraulic retention time, organic loading rate, Maintenance, Nutrient) is studied. Integration of dark fermentation and microbial electrolysis cell is the most trending progression for sustainable bio­hydrogen production. Genetic improvement of microbe for biohydrogen production via inactivation of hydrogenase (H2ase) and improve oxygen tolerant H2ase. In future, bioaugmentation, multidisciplinary integrated process and microbial electrolysis needs to be experimented in industrial level scale for successful commercialization. About 41.47 mmol H2/g DCW h at 40 g/L of optimum biohydrogen production was obtained through glycerol fermentation. From the studies, the cost of biohydrogen production was found to high with respect to the direct bio photolysis it cost around $7.24 kg-1; for indirect bio photolysis it cost around $7.54 kg-1 and for fermentation it cost around $7.61 kg-1.

Bio-hydrogen-producing Potential Evaluation and Capacity Enhancement from Tobacco Processing Leftovers by Photo-fermentation Under Diverse Initial pH.

The use of tobacco growing and processing residues for bio-hydrogen production is an effective exploration to broaden the source of bio-hydrogen production raw materials and realize waste recycling. In this study, bio-hydrogen-producing potential was evaluated and the effect of diverse initial pH on hydrogen production performance was investigated. The cumulative hydrogen yield (CHY) and the properties of fermentation liquid were monitored. The modified Gompertz model was adopted to analyze the kinetic characteristics of photo-fermentation bio-hydrogen production process. Results showed that CHY increased firstly and then decreased with the increase of initial pH. Highest CHY and hydrogen production rate of appeared at the initial pH of 8, which were 257.7 mL and 6.15 mL/h, respectively. The acidic initial pH was found to severely limit the bio-hydrogen production capacity. The correlation coefficients (R2) of hydrogen production kinetics parameters were all greater than 0.99, meaning that the fitting effect was good. The main metabolites of bacteria in the system were acetic acid, butyric acid, and ethanol, and the consumption of acetic acid was promoted with the increase of initial pH.

Two-Stage Bio-Hydrogen and Polyhydroxyalkanoate Production: Upcycling of Spent Coffee Grounds.

Coffee waste is an abundant biomass that can be converted into high value chemical products, and is used in various renewable biological processes. In this study, oil was extracted from spent coffee grounds (SCGs) and used for polyhydroxyalkanoate (PHA) production through Pseudomonas resinovorans. The oil-extracted SCGs (OESCGs) were hydrolyzed and used for biohydrogen production through Clostridium butyricum DSM10702. The oil extraction yield through n-hexane was 14.4%, which accounted for 97% of the oil present in the SCGs. OESCG hydrolysate (OESCGH) had a sugar concentration of 32.26 g/L, which was 15.4% higher than that of the SCG hydrolysate (SCGH) (27.96 g/L). Hydrogen production using these substrates was 181.19 mL and 136.58 mL in OESCGH and SCGH media, respectively. The consumed sugar concentration was 6.77 g/L in OESCGH and 5.09 g/L in SCGH media. VFA production with OESCGH (3.58 g/L) increased by 40.9% compared with SCGH (2.54 g/L). In addition, in a fed-batch culture using the extracted oil, cell dry weight was 5.4 g/L, PHA was 1.6 g/L, and PHA contents were 29.5% at 24 h.

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.

Surfactant induced microwave disintegration for enhanced biohydrogen production from macroalgae biomass: Thermodynamics and energetics.

This research work aimed about the enhanced bio-hydrogen production from marine macro algal biomass (Ulva reticulate) through surfactant induced microwave disintegration (SIMD). Microwave disintegration (MD) was performed by varying the power from 90 to 630 W and time from 0 to 40 min. The maximum chemical oxygen demand (COD) solubilisation of 27.9% was achieved for MD at the optimal power (40%). A surfactant, ammonium dodecyl sulphate (ADS) is introduced in optimal power of MD which enhanced the solubilisation to 34.2% at 0.0035 g ADS/g TS dosage. The combined SIMD pretreatment significantly reduce the treatment time and increases the COD solubilisation when compared to MD. Maximum hydrogen yield of 54.9 mL H2 /g COD was observed for SIMD than other samples. In energy analysis, it was identified that SIMD was energy efficient process compared to others since SIMD achieved energy ratio of 1.04 which is higher than MD (0.38).

Effect of 5-HMF and furfural additives on bio-hydrogen production by photo-fermentation from giant reed.

Substances harmful to photo-fermentative biological hydrogen production (PFHP) were produced during cellulose hydrolysis. This study aimed to evaluate the effect of by-products (5-hydroxymethylfurfural (5-HMF) and furfural) released from lignocellulose during enzymatic hydrolysis process on PFHP. The exist of 5-HMF inhibited the hydrogen production. However, 0.2 g/L furfural improved the hydrogen production by 19 % compared to no addition (511.6 mL) with a maximum concentration of nitrogenase (109.96 IU/L) at 96 h. Furthermore, a 18.7 % enhancement of hydrogen production was also observed when 0.2 g/L 5-HMF and furfural were mixed at a ratio of 1:1, while decrement of hydrogen production at higher addition was observed as well. Through the scatter matrix analysis, it was concluded that 5-HMF and furfural additives had significant effects on PFHP. This study gave an insight into effect of lignocellulosic by-products on biohydrogen production.

Comparison of three ionic liquids pretreatment of Arundo donax L. For enhanced photo-fermentative hydrogen production.

Ionic liquids (ILs) pretreatment has been regarded as a promising green way to treat lignocellulosic biomass. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-Butyl-3-methylimidazolium Hydrogen Sulfate ([Bmim]HSO4) with different loadings (2, 4, 8, and 16 g/L) were adopted to pretreat the Arundo donax L.. 16 g/L [Bmim]HSO4 pretreated Arundo donax L. obtained the highest sugar yield of 7.9 g/L during the enzymatic hydrolysis and hydrogen yield of 106.1 mL/g TS during the photo-fermentation, which were 68.8 % and 35.3 % higher than those of untreated Arundo donax L., respectively. Moreover, volatile fatty acids (VFAs) distribution revealed that acetic acid was the main by-product during hydrogen production process with ILs pretreated Arundo donax L.. Besides, the relationship between sugar yield and hydrogen yield was the closest based on scatter matrix analysis. This study helps to understand of correlation between ILs pretreatment with the behavior of bioenergy production.

Household food waste conversion to biohydrogen via steam gasification over copper and nickel-loaded SBA-15 catalysts.

Household food waste (FW) was converted into biohydrogen-rich gas via steam gasification over Ni and bimetallic Ni (Cu-Ni and Co-Ni) catalysts supported on mesoporous SBA-15. The effect of catalyst method on steam gasification efficiency of each catalyst was investigated using incipient wetness impregnation, deposition precipitation, and ethylenediaminetetraacetic acid metal complex impregnation methods. H2-TPR confirmed the synergistic interaction of the dopants (Co and Cu) and Ni. Furthermore, XRD and HR-TEM revealed that the size of the Ni particle varied depending on the method of catalyst synthesis, confirming the formation of solid solutions in Co- or Cu-doped Ni/SBA-15 catalysts due to dopant insertion into the Ni. Notably, the exceptional activity of the Cu-Ni/SBA-15-EMC catalyst in FW steam gasification was attributed to the fine distribution of the concise Ni nanoparticles (9 nm), which resulted in the highest hydrogen selectivity (62 vol%), gas yield (73.6 wt%). Likewise, Cu-Ni solid solution decreased coke to 0.08 wt%.

Dataset of response characteristics of H2-producing bacteria consortium to ß-lactams, aminoglycosides, macrolides, quinolones antibiotics.

Antibiotics on H2 producing bacteria shall be considered as being one of the critical elements in biological H2 production utilizing livestock manure as raw resources. Despite the fact that the manure stands a significance role in bio-fermentation, the possibility of antibiotics being contained in excreta shall not be eliminated. Findings of whether the above saying might threaten the safety of bio-H2 production needs to be further studied. The experiment subjects include: six single and three combined antibiotics were tested and analyzed by the application of the gradient experiment method. Along with the H2 production rate, CHO content, pH and OD600 were used to analyze the effects of various antibiotics introduction on the hydrolysis, fermentation and H2 production. To a further extent, four typical representative samples were selected for biodiversity analysis from the single antibiotic experiment groups. Amounting more than 6000 pieces of data were obtained in a series of experiments. Data suggested that remarkable measure of antibiotics have various degrees of H2 production inhibition, while some antibiotics, Penicillin G, Streptomycin Sulfate, and their compound antibiotics, could promote the growth of Ethanoligenens sp. and improve H2 yield in the contrary. Correspondent to the transition of key metabolic intermediates and end products, the mechanism of each antibiotic type and dose on H2 production were summarized as follows: the main inhibitory mechanisms were: (1) board-spectrum inhibition, (2) partial inhibition, (3) H2 consumption enhancement; and the enhancement mechanisms were: (1) enhance the growth of H2-producing bacteria, (2) enhanced starch hydrolysis, (3) inhibitory H2 consumption or release of acid inhibition. Meanwhile, data analysis found that the effect of antibiotics on H2 producing was not only related to type, but also to dosage. Even one kind of antibiotic may have completely opposite effects on H2-producing bacteria under different dosage conditions. Inhibition of H2 yield was highest with Levofloxacin at 6.15 mg/L, gas production was reduced by 88.77%; and enhancement of H2 yield was highest with Penicillin G at 7.20 mg/L, the gas production increased by 72.90%.