Thermophilic Dark Fermentation Research Articles

Enhanced thermophilic dark fermentation of hydrogen production from food waste by Fe-modified biochar

The industrialization of hydrogen production through dark fermentation of food waste faces challenges, such as low yields and unpredictable fermentation processes. Biochar has emerged as a promising green additive to enhance hydrogen production in dark fermentation. Our study demonstrated that the introduction of Fe-modified biochar (Fe-L600) significantly boosted hydrogen production during thermophilic dark fermentation of food waste. The addition of Fe-L600 led to a remarkable 31.19% increase in hydrogen yield and shortened the time needed for achieving stabilization of hydrogen production from 18 h to 12 h. The metabolite analysis revealed an enhancement in the butyric acid pathway as the molar ratio of acetic acid to butyric acid decreased from 3.09 to 2.69 but hydrogen yield increased from 57.12 ± 1.48 to 76.78 ± 2.77 mL/g, indicating Fe-L600 improved hydrogen yield by regulating crucial metabolic pathways of hydrogen production. The addition of Fe-L600 also promoted the release of Fe2+ and Fe3+ and increased the concentrations of Fe2+ and Fe3+ in the fermentation system, which might promote the activity of hydrogenase and ferredoxin. Microbial community analysis indicated a substantial increase in the relative abundance of Thermoanaerobacterium after thermophilic dark fermentation. The relative abundances of microorganisms responsible for hydrolysis and acidogenesis were also observed to be improved in the system with Fe-L600 addition. This research provides a feasible strategy for improving hydrogen production of food waste and deepens the understanding of the mechanisms of biochar.

Comparison analysis on biohydrogen production of mesophilic and thermophilic dark fermentation using nickel doped lanthanum-iron oxide nanoparticles as supplementation

In this work, perovskite-structured LaNi0.5Fe0.5O3 nanoparticles (NPs) are successfully synthesized to explore influence of addition amounts on biohydrogen yield. The great potential advantages to improve the biohydrogen production under mesophilic and thermophilic dark fermentation are systematically investigated by a series of experiments. The characterization of physicochemical properties of LaNi0.5Fe0.5O3 NPs are summarized and analyzed. The highest biohydrogen yield 262.55 mL/g of mesophilic dark fermentation is obtained at 100 mg/L LaNi0.5Fe0.5O3 NPs group while under thermophilic condition, the maximum of biohydrogen production is only 182.13 mL/g with 200 mg/L LaNi0.5Fe0.5O3 supplementation, which are higher 50.7% and 91.0% than that of corresponding control groups, respectively. The analysis of soluble microbial products (SMPs) suggests that LaNi0.5Fe0.5O3 NPs can observably enhance the butyrate-type metabolic pathway, being consistent with the raising abundance of Clostridium butyricum in mesophilic fermentation. The extracellular polymer content is significantly increased with appropriate addition of LaNi0.5Fe0.5O3 NPs. The results reveal that the moderate amount of LaNi0.5Fe0.5O3 NPs can even optimize the microbial community structure by increasing the abundance of Clostridium sensu stricto 1 under mesophilic fermentation and Clostridium sensu stricto 7 as well as Longonea under thermophilic fermentation. Eventually, it can be affirmatively concluded that the application of LaNi0.5Fe0.5O3 NPs to dark fermentation contributes to more biohydrogen yield with moderate amounts under both mesophilic and thermophilic conditions. The innovative work of nickel doped lanthanum-iron oxide nanoparticles provides an effective strategy to take the fully advantage of Fe and Ni element for biohydrogen yield.

Maximization of Energy Recovery from Starch Processing Wastewater by Thermophilic Dark Fermentation Coupled with Microbial fuel Cell Technology

Utilization of organic wastewater for hydrogen production has dual advantages of clean energy generation and bioremediation, which is sustainable for a longer period. To maximize the energy recovery from starch rich wastewater, a two stage system comprising of thermophilic dark fermentation coupled with microbial fuel cell was employed. A single parameter optimization strategy was implemented for the operation of the batch system. The maximum cumulative hydrogen production obtained was 2.56 L L−1 with a 48% reduction in COD under the optimal conditions of 35 g L−1 initial substrate concentration (COD), temperature 60 °C, and pH 6.5. The H2 yield and H2 production rate were 6.8 mol H2/kg CODreduced and 731.3 mL L−1 h−1, respectively. The effect of the organic loading rate (OLR) on H2 production rate was studied in a continuous stirred tank reactor (CSTR). A maximum hydrogen production rate of 913 mL L−1 h−1 was observed at an OLR of 5.6 g L−1 h−1. Effluent recycle played an important role in the improvement of H2 production. A maximum H2 production rate of 1224 mL L−1 h−1 was observed at a recycle ratio of 0.6. Power density of 4.2 W m−3 was observed with MFC using the dark fermentative spent media neutralized with carbonate buffer at an optimal pH of 7. A total COD reduction of 86% was observed.

Enhanced fermentative biohydrogen production from milk processing wastewater by magnetic spinel ferrites nanoparticles

ABSTRACT In the present study, metal ferrites nanoparticles (MFNPs), comprising nickel ferrite (NiFe2O4), cobalt ferrite (CoFe2O4), and copper ferrite (CuFe2O4) nanoparticles (NPs), were synthesized and characterized for investigating their effect on biohydrogen production by thermophilic dark fermentation of milk processing wastewater (MPWW). The MFNPs were synthesized using the chemical coprecipitation method and were characterized using XRD, SEM-EDS, and VSM analysis. According to the characterization results, the average nanocrystallite sizes of NiFe2O4, CoFe2O4 and CuFe2O4 spinels were 25.8 nm, 33 nm, and 20.7 nm, respectively. The NPs prepared were pure and showed a ferromagnetic behavior. Dark fermentation tests revealed that the MFNPs had a promoting effect on biohydrogen production. In comparison with the control assay, biohydrogen yield was enhanced by 2.71, 2.58, and 2 folds higher for optimal concentrations of CuFe2O4, NiFe2O4, and CoFe2O4, respectively. The maximum biohydrogen yield of 246.13 ± 3.69 mL/g VS was obtained by adding 2 mg/L of CuFe2O4 NPs. The experimental data of MFNPs-assisted dark fermentation were well predicted by the Gompertz kinetic model.

Volatile fatty acids and ammonia recovery, simultaneously cathodic hydrogen production and increasing thermophilic dark fermentation of food waste efficiency

A combined thermophilic anaerobic bioreactor of food waste and bioelectrodialysis system was used to recover volatile fatty acids and ammonia as renewable materials and also to remove the inhibitory effect of biohydrogen production byproducts. Different configurations of bioelectrodialysis system under various amounts of inlet food waste and external electrical currents were examined were investigated to find out the best conditions for system performance. When the two anion exchange membranes (AEM) were installed on the anode and cathode sides of separation chamber, 12 mL min-1 of mixed liquid was circulated between fermenter and separation chamber, while the external energy of 2.7 V and 0.2 M NaCl as electrolyte were used in the electrodialysis chambers. As long as the food waste with 70000 mg COD L-1 was used in the fermenter, the concertation of organic acids in the recovery chamber was the highest, 507.3 mg L-1 after 24th h. As a result, 0.63 L L-1 biohydrogen and 50 mL cathodic hydrogen were produced. When a cation exchange membrane was embedded on the cathode side of the separation chamber, the ammonia concertation in the recovery chamber was the highest, 518 mg L-1, at 36th h. At the same time, the chemical oxygen demand of the anode solution was decreased by about 3600 mg L-1. This sustainable and bioelectrical system can recover organic acids and ammonia, cathodic hydrogen production, while simultaneously increase biohydrogen production and efficient even when substrate concentration was higher.

Thermophilic dark fermentation fast start-up of hydrogen production with substrate concentration regulation and moderate pretreatment inoculum

Accelerating start-up of thermophilic dark fermentation would improve hydrogen production efficiency was investigated. To find an efficient method for accelerating start-up and explore the effect of inoculum type for hydrogen production system, three thermophilic hydrogen production EGSB (expanded granular sludge bed) reactors equipped with flocculent or granular sludge using different startup modes were constructed in this study. Among three reactors under butyric acid type of fermentation, EGSB3 (startup mode: pretreated granular sludge as inoculum and regulated substrate concentration) was the most efficient one with shortest start-up time (13 days) and maximum hydrogen production (1.64 mol H2/mol glucose). EGSB1 (startup mode: pretreated flocculent sludge as inoculum and regulated substrate concentration) was started up in 27 days at 1.27 mol H2/mol glucose in maximum. While EGSB2 (startup mode: original granular sludge as inoculum and without regulating substrate concentration) took 46 days for start-up and the 1.6 mol H2/mol glucose hydrogen producing rate was obtained. After start-up, the dominant hydrogen production bacteria were Thermoanaerobacterium thermosaccharolyticum strain TG57 in three reactors. EGSB3 reactor owned the most proportion with 53.21 % than others. In all, mild pretreatment and regulating substrate concentration for granular sludge would be benefit for fast startup of thermophilic dark fermentation hydrogen production leading to shortest startup time, high hydrogen production efficiency and most functional microorganism.

A combined system for asbestos-cement waste degradation by dark fermentation and resulting supernatant valorization in anaerobic digestion

The use of biological processes for the treatment of asbestos cement waste (ACW) has gained interest in recent years. Nevertheless, this methodology is not yet consolidated because of the incomplete ACW conversion during the biological treatment and the consequent need for further treatments that generally require a high amount of energy and chemicals. In this study, the efficiency of both mesophilic and thermophilic dark fermentation (DF) fed with glucose in fed-batch conditions was assessed for ACW biological treatment. Both thermophilic and mesophilic DF of glucose resulted in a partial conversion of glucose into organic acids that successfully degraded all the asbestos fibers contained in an ACW sample. A hydrogen-rich biogas was produced as well: at the end of the mesophilic DF treatment 0.14 LH2 gglucose−1 were obtained. In addition, the anaerobic digestion (AD) of the DF supernatants led to the production of 0.38 LCH4 gCOD−1.

Thermophilic Dark Fermentation of Olive Mill Wastewater in Batch Reactors: Effect of pH and Organic Loading

In recent decades, olive oil consumption has almost tripled worldwide. Olive oil production is linked with the production of enormous amounts of olive mill wastewater, the main by-product derived from three-phase olive mills. Due to the environmental risks of olive mill wastewater disposal, the management and valorization of the specific waste stream is of great importance. This work focuses on the thermophilic dark fermentation of olive mill wastewater in batch reactors, targeting pH optimization and the organic loading effect. A series of experiments were performed, during which the organic load of the substrate remained at 40 g/L after dilution with tap water, and the pH was tested in the range of 4.5 to 7.5. The maximum yield in terms of produced hydrogen was obtained at pH 6.0, and the yields were 0.7 mol H2/mol glucose or 0.5 L H2/Lreactor. At the same conditions, a reduction of 62% of the waste’s phenols was achieved. However, concerning the effect of organic loading at the optimized pH value (6.0), a further increase in the organic load minimized the hydrogen production, and the overall process was strongly inhibited.

Manganese ferrite nanoparticles enhanced biohydrogen production from mesophilic and thermophilic dark fermentation

In this work, Manganese ferrite nanoparticles (MnFe 2O4 NPs) were synthesized, and their potential to increase the biohydrogen (bio-H2) yield of glucose in mesophilic and thermophilic fermentations was evaluated. Material characterization showed that the MnFe 2O4 NPs were perfectly synthesized, with a specific surface area of 43.97 m2g−1. Both mesophilic and thermophilic fermentation obtained the highest bio-H2 yields of 272.7 and 183.4 mL H2/g glucose in the 400 mg/L MnFe 2O4 NPs group, which values were increased by 40.1% and 131.9% (37 °C and 55 °C), respectively, compared to their control groups. Soluble microbial products (SMPs) showed that MnFe 2O4 NPs enhanced the butyrate pathway. Three-dimensional fluorescence spectroscopy analysis showed that MnFe 2O4 NPs increased the extracellular polymer content of anaerobic sludge. The results showed that MnFe 2O4 NPs distinctly increased the abundance of Clostridium_sensu_stricto 1 (39.49%) in the microbial community during mesophilic fermentation and improved the abundance of the dominant bacteria Clostridium_sensu_stricto_7 (25.59%) and Longlinea (21.36%) during thermophilic fermentation. Real-time PCR analysis showed that hydrogenase gene (hycl) expression increased exponentially after the addition of MnFe 2O4 NPs, and increasing the fermentation temperature improved the hydrogenase activity. We found that MnFe 2O4 NPs promoted to bio-H2 production in both mesophilic and thermophilic fermentation, and it contributed more significantly to thermophilic fermentation than mesophilic fermentation.

Reactor start-up strategy as key for high and stable hydrogen production from cheese whey thermophilic dark fermentation

Using the right start-up strategy can be vital for successful hydrogen production from thermophilic dark fermentation (55 °C), but it needs to be affordable. Hence, three start-up strategies modifying only influent concentration and temperature were assessed in a reactor fed with cheese whey: (i) high temperature (55 °C) and a high organic loading rate (OLRA - 15 kgCOD m−3 d−1) right at the beginning of the operation; (ii) slowly increasing temperature up to 55 °C using a high OLRA and (iii) slowly increasing temperature and OLRA up to the desired condition. Strategy (iii) increased hydrogen productivity in 39% compared to the others. The combination of high temperature and low pH thermodynamically favored H2 producing routes. Synergy between Thermoanaerobacterium and Clostridium might have boosted hydrogen production. Three reactors of 41 m³ each would be needed to treat 3.4 × 103 m3 year−1 of whey (small-size dairy industry) and the energy produced could reach 14 MWh month−1.

Dynamics of sulfate reduction in the thermophilic dark fermentation of sugarcane vinasse: A biohydrogen-independent approach targeting enhanced bioenergy production

Dark fermentation (DF) systems usually exploit bioH2 production aiming to improve the energetic potential (EP) of anaerobic digestion (AD) schemes. In the case of sulfate-rich substrates, the versatility of fermentative consortia may favor the establishment of sulfidogenic conditions, minimizing/eliminating the competition between sulfate-reducing bacteria (SRB) and methanogens in the sequential stage and providing sulfide-free biogas. This study details the establishment of sulfidogenesis on the thermophilic DF of sugarcane vinasse in a continuous polyurethane-filled fixed-film reactor, also estimating the EP for vinasses according to different AD-related approaches. High sodium levels naturally stimulated SRB by maintaining high pH values (> 6.0), whilst NaHCO3 dosing was required when natural buffering conditions were not maintained. High acetate (~ 3 g-COD L−1) and COD/sulfate ratio (> 25.0) levels indicated a high-quality substrate for further methanogenesis. High butyrate concentrations (~11 g-COD L−1) coupled to caproate detection indicated the occurrence of chain elongation processes, leading to low bioH2 production levels (<400 NmL-H2 L−1 d−1). However, estimates indicated 12.2%- and 51.7%-increases in the methane-based EP (MJ m−3) of sulfate-free fermented vinasse (216.72) relative to sulfate-rich fermented (193.10) and fresh (142.88) vinasses. Hence, the ultimate approach for maximizing bioenergy production from sugarcane vinasse is detailed in this study.

Comparison of mesophilic and thermophilic dark fermentation with nickel ferrite nanoparticles supplementation for biohydrogen production

In this work, nickel ferrite nanoparticles (NiFe2O4 NPs) was prepared to improve hydrogen (H2) production by dark fermentation. Moderate amounts (50–200 mg/L) promoted H2 generation, while excess NiFe2O4 NPs (over 400 mg/L) lowered H2 productivity. The highest H2 yields of 222 and 130 mL/g glucose were obtained in the 100 mg/L (37 °C) and 200 mg/L NiFe2O4 NPs (55 °C) groups, respectively, and the values were 38.6% and 28.3% higher than those in the control groups (37 °C and 55 °C). Soluble metabolites showed that NiFe2O4 NPs enhanced the butyrate pathway, corresponding to the increased abundance of Clostridium butyricum in mesophilic fermentation. The endocytosis of NiFe2O4 NPs indicated that the released iron and nickel favored ferredoxin and hydrogenase synthesis and activity and that NiFe2O4 NPs could act as carriers in intracellular electron transfer. The NPs also optimized microbial community structure and increased the levels of extracellular polymeric substances, leading to increased H2 production.

Biohythane production from food waste in a two-stage process: assessing the energy recovery potential

ABSTRACT Biohythane (hydrogen + methane) production in a two stage dark fermentation (DF) and anaerobic digestion (AD) process from food waste (FW) has been studied. This paper investigated the effect of operation temperature, i.e. mesophilic (34 °C) and thermophilic (55 °C) , on biohythane yield and total energy recovery carried out at the initial culture pH 5.5 and pH 7, respectively for DF and AD batch tests. The mesophilic DF tests gave a higher hydrogen yield of 53.5 (4) mL H2/g VS added compared to thermophilic DF tests, i.e. 37.6 (1) mL H2/g VS added. However, higher methane yields, i.e. 307.5 ( 10) mL CH4/g VS, were obtained at thermophilic AD tests compared to mesophilic AD, i.e. 276.5 (4.3) mL CH4/g VS. The total energy recovery from thermophilic DF + AD was higher (11.4 MJ/kg VS) than the mesophilic (10.4 MJ/kg VS) combined process. Interestingly, the analysis of kinetic parameters of mesophilic tests, determined from the Modified Gompertz equation, showed that mesophilic DF had faster H2 production kinetics, which can be attributed to a faster adaptation of the heat-shocked inoculum used in the tests to the incubation temperature. However, thermophilic AD tests exhibited faster kinetics for methane production.

Molasses vs. juice: Maximizing biohydrogen production in sugarcane biorefineries to diversify renewable energy generation

Diversifying the portfolio of bioenergy-related products in sugarcane biorefineries is required to increase substrate conversion efficiency and market reach. The suitability of producing biohydrogen (bioH2) through the thermophilic dark fermentation of juice and molasses was assessed as an alternative to conventional sugarcane processing. The energetic potential of applying anaerobic digestion with phase separation to process molasses was also investigated. Molasses outperformed juice as substrate for continuous bioH2 production due to a more balanced nutrient content, whilst nitrogen deficiency directly hindered juice fermentation. An optimal COD/N ratio (∼100) could maximize bioH2 production from both juice and molasses. Continuous bioH2 production from molasses fermentation was optimized at pH and organic loading rate values of 5.38 and 86 kg-COD m−3 d-1, which are consistent with acidogenic systems inoculated with sugarcane vinasse-derived consortia. Metabolite profiles suggested that capnophilic lactic fermentation coupled to lactate-based butyrate production were the primary conversion pathways. Bioenergy generation from molasses (bioH2 + methane) exceeded that of vinasse by over 600 %, highlighting the relevance of anaerobic digestion as an efficient core processing step in the sucroenergetic industry. In particular, phase separation enhanced the total energy production by 13.1 % (604.30 vs. 683.76 MJ per ton of sugarcane) by maximizing the methane yield up to theoretical values.

Thermoanaerobacterium sp. Strain RBIITD as a dominant species in accelerating thermophilic dark fermentation start up through pH and substrate concentration regulation

In this work, accelerated start-up of biological hydrogen production system fed with glucose and molasses at 55 °C by regulating pH and COD concentration was investigated in two groups. Then three reactors in each group were compared: controlling pH, controlling pH with COD, and controlling the COD. The reactors in group A presented best hydrogen yield of 1.84 mol H2/mol glucose·day and worked stably at the 8th day. The highest hydrogen yield in group B was 2.13 mol H2/mol molasses·day and steadily at the 11th day. It proved that controlling two key parameters of the inflow pH (8.0) and substrate concentration (4000 mg COD/L) could realize fast start-up of hydrogen production reactor. This study demonstrated that Thermoanaerobacterium sp. strain RBIITD could produce hydrogen and provide a new avenue for biological hydrogen production by dark fermentation using cheap substrate towards a more sustainable and feasible technology.

Mesophilic and thermophilic dark fermentation course analysis using sensor matrices and chromatographic techniques

Production of biofuels from biomass is expected to benefit the society and the environment. At present, bio waste residues processing includes hydrolysis, dark fermentation, photofermentation, pyrolysis, gasification, and chemical synthesis. As the composition and the chemical structure of organic substances affect the efficiency of mentioned processes, it is believed that the glucose concentration is a crucial parameter for the evaluation of the efficiency of biological processes. Also, the control of by-products formulated during each stage of biomass processing affects the course of dark fermentation. Therefore, model processes regarding mesophilic and thermophilic dark fermentation were carried out. Glucose as a sole carbon source was applied as the fermentation broth and Faloye-pretreated activated municipal wastewater sludge was introduced as the source of sporulating microorganisms. Production of hydrogen and methane was controlled by means of sensor matrices. Obtained results are comparable to those obtained using the standard method based on gas chromatography and indicate the suitability of their application for online routine analyses of hydrogen and methane during fermentation processes. In addition, the fermentation broth was also examined by means of gas and liquid chromatography in the scope of glucose reduction, and generation of volatile fatty acids and phenols.

Early warning indicators and microbial community dynamics during unstable stages of continuous hydrogen production from food wastes by thermophilic dark fermentation

Early warning indicators (EWIs) and microbial community dynamics during thermophilic dark fermentation-based hydrogen production (TFHP) from food wastes were investigated during stable and fluctuating operations in continuous systems. Difference and redundancy analyses revealed the linkage between dominant genera, metabolites and process parameters and characterized the EWIs and mechanism of instability of the TFHP. Besides biogas production rate (GPR), hydrogen proportion and volatile fatty acids (VFAs) concentrations, the potential warning function of the microbial community were observed. Thermoanaerobacterium was the dominant genus which decreased during the unstable stages. Bacillus is another EWI in unstable stages when the value of pH is lower. Lactobacillus and Weissella appeared as OLR increased to 9 g VS L−1 d−1 in the OLR-9 unstable stage. This study demonstrates the key EWIs for monitoring and controlling continuous hydrogen production and its stability.

Novel insights on the versatility of biohydrogen production from sugarcane vinasse via thermophilic dark fermentation: Impacts of pH-driven operating strategies on acidogenesis metabolite profiles

An innovative application of the anaerobic structured-bed reactor (AnSTBR) in thermophilic dark fermentation of sugarcane vinasse targeting biohydrogen (bioH2) production was assessed. A detailed metabolite monitoring program identified the major substrates and primary metabolic pathways within the system. Increasing the applied organic loading rate positively affected bioH2 production, reaching 2074 N mL-H2 L−1 d−1 and indicating an optimal load of approximately 70 kg-COD m−3 d−1. Controlling the fermentation pH (5.0–5.5) was the primary strategy to maintain bioH2-producing conditions, offsetting negative impacts associated with the compositional variability of vinasse. Metabolic correlations pointed out lactate as the primary substrate for bioH2 production, indicating its accumulation as evidence of impaired reactors. The versatility of the acidogenic system was confirmed by identifying three major metabolic pathways according to the pH, i.e., lactate-producing (pH <5.0), bioH2-/butyrate-producing (pH = 5.0–5.5) and bioH2-producing/sulfate-reducing (pH >6.0) systems, which enables managing the operation of the reactors for diversified purposes in practical aspects.

Thermophilic biohydrogen recovery from palm oil mill effluent

Enhancement of biological H2 production efficiency with pre-ozonation process of palm oil mill effluent (POME) prior to thermophilic dark fermentation (55 °C) was investigated. H2 fermentation experiments were conducted using varying concentrations of raw and ozonated POME. Results revealed that H2 can be produced from both raw and ozonated POME under thermophilic fermentation. Maximum H2 production yield of 77 mL.g−1CODremoved was obtained from ozonated POME, which was higher than that of 51 mL·g−1 CODremoved obtained from raw POME at the highest concentration of 35,000 mg COD.L−1. Meanwhile, the specific H2 production rate (R'max) of 1.9 and 1.5 mL·h−1·g−1 TVS were observed in raw and ozonated POME at the concentration of 25,000 mg COD.L−1, respectively. The main metabolic products during POME fermentation were acetic and butyric acids and trace amount of valeric acid. Propionic acid and ethanol have contributed, which could be reduced H2 production in all batch experiments for both POME. The highest efficiency of total and soluble COD removal of 24 and 25% was obtained from the raw POME, and those of 19 and 25% was obtained from the ozonated POME. The present study demonstrates that the POME loading was greatly influenced on the H2 production yields and rates. The comparative results showed that the ozonated POME gave higher H2 yields than the raw POME. Thus, demonstrating that the ozonation process significantly improved the POME biodegradability, which is able to enhance H2 production yields. However, the ozone pre-treatment was not improved in the specific H2 production rates.

Inoculum pretreatment differentially affects the active microbial community performing mesophilic and thermophilic dark fermentation of xylose

The influence of different inoculum pretreatments (pH and temperature shocks) on mesophilic (37 °C) and thermophilic (55 °C) dark fermentative H2 production from xylose (50 mM) and, for the first time, on the composition of the active microbial community was evaluated. At 37 °C, an acidic shock (pH 3, 24 h) resulted in the highest yield of 0.8 mol H2 mol−1 xylose. The H2 and butyrate yield correlated with the relative abundance of Clostridiaceae in the mesophilic active microbial community, whereas Lactobacillaceae were the most abundant non-hydrogenic competitors according to RNA-based analysis. At 55 °C, Clostridium and Thermoanaerobacterium were linked to H2 production, but only an alkaline shock (pH 10, 24 h) repressed lactate production, resulting in the highest yield of 1.2 mol H2 mol−1 xylose. This study showed that pretreatments differentially affect the structure and productivity of the active mesophilic and thermophilic microbial community developed from an inoculum.