Dark Fermentation Effluent Research Articles

Continuous dark and photo biohydrogen production in a baffled bioreactor and electrons distribution analysis

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 H2 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.

Polyhydroxybutyrate production from dark-fermentative effluent and composite grafting with bagasse derived α-cellulose in a biorefinery approach

The study evaluated the preparation of a biocomposite using waste-derived polyhydroxybutyrate (PHB) and bagasse cellulose (α-cellulose) in a biorefinery approach. PHB was produced using dark fermentation effluent rich in volatile fatty acids (VFA) derived from vegetable waste and α-cellulose was extracted from sugarcane bagasse (SCB). Nutrient limitation induced microbial PHB accumulation, wherein maximum production of 0.28 ± 0.06 g PHB/g DCW (28%) was observed. Confocal examination showed the deposition of PHB granules in the cell cytoplasm and NMR spectrum exhibited a structural correlation. α-Cellulose (0.22 ± 0.02 g α-cellulose/g SCB) was extracted through SCB pretreatment. Thereafter, grafting α-cellulose with PHB offered intermolecular bonding, which resulted in enhanced thermal stability of the biocomposite than corresponding pristine PHB. FE-SEM morphological examination of biocomposite depicted that α-cellulose functioned as a filler to PHB. XRD profiles showed significant decrement in PHB crystallinity, signifying the functional role of α-cellulose as an effective reinforcing agent. Additionally, ether functional group of α-cellulose and ester group of PHB also appeared in XPS analysis of the composite, thus authorizing the effective blending of α-cellulose and PHB. Utilization of bagasse-derived cellulose for strengthening biologically produced PHB expands its applications, while simultaneously addressing the plastic pollution issues. Additional value from this process was further achieved by incorporating the concept of biorefinery, wherein acidogenic fermentation effluents were used for the production of PHA, which enabled the re-entry of products (VFA) to the production cycle, thus achieving circularity.

A Review of Suitable Substrates for Hydrogen Production in Microbial Electrolysis Cells

Microbial electrolysis cells (MECs) represent a renewable hydrogen production technology that offers the possibility of converting wastewater to hydrogen through a bioelectrochemical process. Particularly, the MEC substrate has a significant effect on the performance of MECs, and in this review, the performances of over 30 substrates examined since 2015 are summarized and compared. It was evident that popular MEC substrates include dark fermentation effluents, pyrolysis products, and raw wastewaters. Additionally, the different MEC substrates investigated yielded different MEC performances, indicating that further studies are required before MECs can become a mature technology for up-scale applications.

Potentiostatic vs galvanostatic operation of a Microbial Electrolysis Cell for ammonium recovery and biogas upgrading

The experimental study reports the performance of a three-chamber Microbial Electrolysis Cell equipped with a two-side cathode, which combines the COD removal in the intermediate anodic chamber, the CO2 removal from a gas mixture in the two-side cathode and the recovery of ammonium as a concentrate solution. The MEC anode was fed by a synthetic dark fermentation effluent with a nitrogen load rate of 1.7 g N/Ld while the two-side cathode was operated with a gas mixture containing CO2. Indeed, the MEC configuration permitted the CO2 removal maximization from a N2/CO2 gaseous mixture simulating a biogas in terms of carbon dioxide composition, while the ammonium migration through the cation exchange membrane allowed for the recovery of a 5 times concentrated solution of ammonium. The +0.20 V vs SHE potentiostatic anodic condition and the two different galvanostatic conditions allowed the removal of 4.21 gCO2/Ld while 700 mg N/Ld were recovered as a concentrated ammonium solution. The current increase set by galvanostatic operation promoted the CO2 removal and ammonium recovery increase by the 113 % and 27 % in comparison with the potentiostatic condition. An increase of the energy consumption was promoted by the galvanostatic condition due to the loss of bioelectrochemical COD oxidation in favour of water oxidation which in turn was caused by the anodic overpotential decrease from 0.85 to 0.52 V.

Single Cell Oil Production by Oleaginous Yeasts Grown in Synthetic and Waste-Derived Volatile Fatty Acids.

Four yeast isolates from the species—Apiotrichum brassicae, Candida tropicalis, Metschnikowia pulcherrima, and Pichia kudriavzevii—previously selected by their oleaginous character and growth flexibility in different carbon sources, were tested for their capacity to convert volatile fatty acids into lipids, in the form of single cell oils. Growth, lipid yields, volatile fatty acids consumption, and long-chain fatty acid profiles were evaluated in media supplemented with seven different volatile fatty acids (acetic, butyric, propionic, isobutyric, valeric, isovaleric, and caproic), and also in a dark fermentation effluent filtrate. Yeasts A. brassicae and P. kudriavzevii attained lipid productivities of more than 40% (w/w), mainly composed of oleic (>40%), palmitic (20%), and stearic (20%) acids, both in synthetic media and in the waste-derived effluent filtrate. These isolates may be potential candidates for single cell oil production in larger scale applications by using alternative carbon sources, combining economic and environmental benefits.

Biohydrogen production in an integrated biosystem using crude glycerol from waste cooking oils

Abstract Biohydrogen production was evaluated in an integrated biosystem, using both dark and photo fermentation, using crude glycerol (CG) derived from the production of biodiesel from waste cooking oils (WCO). The dark fermentation assay was done with 20.0 g COD L−1 of CG by a mixed culture from Clostridiales order at 37 °C, pH 5.5 and generated 24.06 mmol H2 g−1 CODconsumed, with the removal of 45.74% of CG. The dark fermentation effluent (DFE) in concentrations of 1.0, 2.0 and 3.0 g COD L−1 was used in the photo fermentation by a phototrophic bacteria culture of Rhizobiales and Clostridiales order, at 37 °C, pH 7.0 at 18.50 W m−2. The optimum condition was achieved with 1.0 g COD L−1 of DFE and generated 3.94 mmol H2 g−1 CODconsumed, with the removal of 76.10% of COD. The culture was able to consume ethanol (76.86%), acetic acid (95.73%), butyric acid (94.76%) and mainly methanol (99.18%), representing a sustainable alternative for the utilization of CG from WCO.

Role of L-cysteine and iron oxide nanoparticle in affecting hydrogen yield potential and electronic distribution in biohydrogen production from dark fermentation effluents by photo-fermentation

Dark fermentation effluent is a potential substrate for hydrogen production by photosynthetic bacteria(PSB). Influences of adding L-cysteine and Fe3O4 nanoparticles (NPs) on hydrogen production performance and electronic distribution from dark fermentation effluents (DFEs) during photo fermentation hydrogen production(PFHP) process were experimentally studied, as well as the critical kinetic analysis. L-cysteine addition can promote flocculability and cell growth rates of PSB HAU-M1 while addition of 300 mg/L L-cysteine and 100 mg/L Fe3O4 NPs can peak H2 yield from the DFEs, resulting in 29.94% and 29.23% substrate electrons were diverted to H2, respectively. Controlling the adding time interval of L-cysteine and Fe3O4 NPs can improve the activity of nitrogenase without weakening flocculation and increase the hydrogen production, the maximum hydrogen yield of 234.55 ± 7.5 mL was obtained at 12 h interval time, 35.94% substrate electrons diverted towards bio-hydrogen generation, and the corresponding nitrogenase activity increased by 2.12 times as comparing to the control. The modified Gompertz and Han-Levenspiel models were employed to model the effect of the L-cysteine and Fe3O4 NPs on hydrogen production, the predicted critical L-cysteine and Fe3O4 NPs concentrations were 4630.87 and 1969.18 mg/L, respectively.

Photo-fermentation biohydrogen production and electrons distribution from dark fermentation effluents under batch, semi-continuous and continuous modes

In this work, the influence of batch, semi-continuous and continuous mode on biohydrogen production from dark fermentation effluents (DFEs) as substrate and electron distribution was investigated. Results indicated a better H2 production performance was obtained in semi-continuous mode. 50% decanting volume ratio (DVR) and 24 h feeding interval time (FIT) were found to be the best condition. Maximum average H2 production rate (HPR) and H2 yield were obtained of 8.44 mL/h and 1386.22 ± 44.23 mL H2/g TOC, respectively. 37.71% substrate electrons partitioning to hydrogen were detected. For continuous mode, more substrate electrons were diverted toward SMPs with the increasing of HRT due to the fact that longer cell retention, more chances were provided for cell lysis. The bad performance in batch mode ascribed to 56.39% substrate electrons were transferred to cell growth and soluble microbial products (SMPs).

Isolation and characterization of a novel photoheterotrophic strain ‘Rubrivivax benzoatilyticus TERI-CHL1’: Photo fermentative hydrogen production from spent effluent

A novel hydrogen producing photosynthetic bacterial strain identified as ‘Rubrivivax benzoatilyticus TERI-CHL1’ was isolated and purified from ‘TERI-CHL’ consortium’ enriched from the sediment samples of Chilika lagoon in Chilika, Odisha, India. Process parameters; pH & temperature, were optimized to enhance hydrogen production performence strain ‘TERI-CHL1’. Acetate, butyrate, sucrose and the spent effluent (DFE: Dark Fermentation effluent) from dark fermentative hydrogen production, explored to use as feed for monitoring hydrogen production performance of ‘TERI-CHL1’ through photo-heterotrophic growth mode. ‘TERI-CHL1’ produced 86.4 mmol/L of cumulative hydrogen from DFE at pH 7 and 37 °C temperature, with 75% H2 yield efficiency. Hydrogen yield efficiency of ‘TERI-CHL1’ from DFE was 8.74 mol per mole of DFE based fermentable organic acids and sugar. This study is the first report on Rubrivivax benzoatilyticus strain ‘TERI-CHL1’ as a promising microbe for valorisation of organic acid rich spent effluent for photofermentative biohydrogen production from Chilika lagoon.

Lipid Induction in Scenedesmus abundans GH-D11 by Reusing the Volatile Fatty Acids in the Effluent of Dark Anaerobic Fermentation of Biohydrogen.

This study aims to investigate the efficacy of lipid induction in Scenedesmus abundans by adding the effluent from dark fermentation of biohydrogen production. Four sets of experiments were conducted: control (sufficient nitrogen), nitrogen depletion, low concentration (0.3×) effluent addition, and high concentration (0.5×) effluent addition. The addition of low concentration effluent produced the highest biomass and lipid yields of 2.831g/L and 1.238g/L, corresponding to a lipid abundance of 43.72wt%. Furthermore, S. abundans had high removal efficiencies for volatile fatty acids in the effluent (formic acid 100%, acetic acid 100%, propionic acid 98%, lactic acid 84%, and butyric acid 68%), and this is the first study demonstrating the ability of S. abundans in using formic acid and lactic acid to produce biomass and lipids. These results show that S. abundans have great abilities in simultaneous reducing organic acids in the effluent and producing valuable metabolites.

Feasibility of quaternary ammonium and 1,4-diazabicyclo[2.2.2]octane-functionalized anion-exchange membranes for biohydrogen production in microbial electrolysis cells

In this work, two commercialized anion-exchange membranes (AEMs), AMI-7001 and AF49R27, were applied in microbial electrolysis cells (MECs) and compared with a novel AEM (PSEBS CM DBC, functionalized with 1,4-diazabicyclo[2.2.2]octane) to produce biohydrogen. The evaluation regarding the effect of using different AEMs was carried out using simple (acetate) and complex (mixture of acetate, butyrate and propionate to mimic dark fermentation effluent) substrates. The MECs equipped with various AEMs were assessed based on their electrochemical efficiencies, H2 generation capacities and the composition of anodic biofilm communities. pH imbalances, ionic losses and cathodic overpotentials were taken into consideration together with changes to substantial AEM properties (particularly ion-exchange capacity, ionic conductivity, area- and specific resistances) before and after AEMs were applied in the process to describe their potential impact on the behavior of MECs. It was concluded that the MECs which employed the PSEBS CM DBC membrane provided the highest H2 yield and lowest internal losses compared to the two other separators. Therefore, it has the potential to improve MECs.

Sequential dark and photo-fermentative hydrogen gas production from agar embedded molasses

In this study, molasses and dark fermentation effluent were solidified using agar and used for H2 production by dark and photo-fermentation. During dark fermentation, the solid jelly form of molasses enabled a slow release of the substrate to the liquid broth hindering fast pH decreases. The initial total sugar concentration, H2 yield, H2 rate and lag phase in dark fermentation were 36.2 g/L, 226.24 mL H2/g TS, 29.85 mL H2/h and 4.37 h, respectively. Photo-fermentation of 5.77 g TVFA/L embedded dark fermentation effluent did not lead to efficient H2 production. The best performance in photo-fermentation was obtained with 1.55 g TVFA/L containing diluted dark fermentation effluent. The H2 yield, H2 rate and lag phase in photo-fermentation were 870.26 mL H2/g TVFA, 0.913 mL H2/h and 54.07 h, respectively. Embedding concentrated substrate using agar can enhance H2 production performance but only if the release of the substrate does not exceed inhibitory levels and if the rate of diffusion is tolerable for microbial activity.

Optimization of the production of docosahexaenoic fatty acid by the heterotrophic microalga Crypthecodinium cohnii utilizing a dark fermentation effluent

Dark fermentation is an anaerobic digestion process of biowaste, used to produce hydrogen as a fuel, which however releases high amounts of polluting volatile fatty acids in the environment. In order for the process to become more competitive, the acids stream can be utilized through conversion to high added-value docosahexaenoic acid by the microalga Crypthecodinium cohnii. Docosahexaenoic acid is one of the two main omega-3 fatty acids, necessary for human nutrition. The purpose of this work was to optimize the production of omega-3 fatty acids by the cells, utilizing the organic content of a dark fermentation effluent. For that purpose, the effect of different fermentation conditions was examined, such as incubation temperature, nitrogen source and concentration, the addition of chemical modulators, as well as the feeding composition. The volatile fatty acid content of the effluent was totally depleted in a fed-batch culture of the microalga, while the cells accumulated DHA in a percentage of 35.6% of total lipids, when fed with yeast extract or 34.2% when fed with ammonium sulfate. Taking into consideration the economic feasibility of the culture conditions proposed it was concluded that the use of yeast extract could be substituted by the much economic ammonium sulfate.

Enhancement of hydrogen production and energy recovery through electro-fermentation from the dark fermentation effluent of food waste

To enhance hydrogen production efficiency and energy recovery, a sequential dark fermentation and microbial electrochemical cell (MEC) process was evaluated for hydrogen production from food waste. The hydrogen production, electrochemical performance and microbial community dynamics were investigated during startup of the MEC that was inoculated with different sludges. Results suggest that biogas production rates and hydrogen proportions were 0.83 ​L/L d and 92.58%, respectively, using anaerobic digested sludge, which is higher than that of the anaerobic granular sludge (0.55 ​L/L d and 86.21%). The microbial community were predominated by bacterial genus Acetobacterium, Geobacter, Desulfovibrio, and archaeal genus Methanobrevibacter in electrode biofilms and the community structure was relatively stable both in anode and cathode. The sequential system obtained a 53.8% energy recovery rate and enhanced soluble chemical oxygen demand (sCOD) removal rate of 44.3%. This research demonstrated an important approach to utilize dark fermentation effluent to maximize the conversion of fermentation byproducts into hydrogen.

Effects of temperature and dark fermentation effluent on biomethane production in a two-stage up-flow anaerobic sludge fixed-film (UASFF) bioreactor

In a two-stage of up-flow anaerobic sludge fixed-film (UASFF) bioreactor, palm oil mill effluent (POME) wastewater was used as inoculum and substrate to study the biodegradation in association with hydrogen and methane production. During the first stage (H2-UASFF unit), different temperatures (37–70 °C) and hydraulic retention time (HRT) was designed and analyzed using response surface methodology (RSM) for biohydrogen production. In the second stage (CH4-UASFF unit), at 24 h HRT, a continuous experiment was carried out using the same temperature and effluent from H2-UASFF unit (also known as dark fermentation effluent) was used as substrate (12–20 g COD L−1). This study is focusing on the second stage of UASFF bioreactor (i.e. CH4-UASFF) for biomethane production. Studied parameters were designed using Historical Data in RSM. Its effects on methane production rate (MPR), methane yield, biogas percentage and COD removal were analyzed. The relation between initial effluent COD and temperature on biomethane production and overall reactor performance treating POME wastewater were also examined. Results showed that 76% of total COD removal efficiency (TCOD) was achieved using two-stage UASFF bioreactor. The MPR of 15.63 L CH4 d−1, methane yield of 0.803 L CH4 g−1 CODrem.d−1, COD removal efficiency of 66.28% and 93.31% of CH4 at optimum temperature and effluent COD of 54 °C and 12 g COD L−1, respectively were obtained in CH4-UASFF unit. Based on this study, thermophilic temperature and low POME concentration showed a significant impact on biomethane production and more than 70% of TCOD of POME was reduced at 24 h HRT.

Enhancement of bio-hydrogen yield and pH stability in photo fermentation process using dark fermentation effluent as succedaneum

The photo fermentation hydrogen yield from dark fermentation effluents (DFEs) can be promoted by adding corn straw enzymatic hydrolysate adjusts the nutritional composition of DFEs. As compared with the control group (without enzymatic hydrolysate addition), the effect of adding enzymatic hydrolysate make H2 yield increase from 312.54 to 1287.06 mL H2/g TOC, and maximum hydrogen production rate increase 2.14 to 10.23 mL/h. On the other hand, buffer reagents remained in DFEs make which can replace part sodium citrate buffer to maintain pH stability in synchronized saccharification and photosynthetic fermentation process with corn straw as substrate, the best result was observed at the ration of 1:2 (33 mL DFEs, 67 mL sodium citrate buffer) with the hydrogen yield of 436.30 ± 10 mL, and which can cut down the GHG in the life cycle of hydrogen production.

Enhanced hydrogen production by a sequential dark and photo fermentation process: Effects of initial feedstock composition, dilution and microbial population

Two-stage process of dark fermentation (DF) and photo fermentation (PF), using fruit and vegetable waste (FVW) and cheese whey powder (CWP), was used as an approach to enhance the hydrogen (H2) production. FVW and CWP at C/N ratios of 34, 39, 60, 71 and 82 were tested as substrates for DF. Dilution (1:2, 1:5, 1:10) of the DF effluents was used as a coupling strategy. DF effluents with low-butyrate and high lactate concentrations were obtained as a function of an increased C/N ratio, which results in high H2 production during the PF. Maximum overall H2 yields of 793.7 and 695.4 mLH2/gChemical Oxygen Demand (COD) were obtained using a 1:10 dilution, at a C/N ratio of 60 and 70, respectively. These H2 yields were higher than those obtained with the individual processes. The C/N ratio at the DF stage regulate not only H2 production but also the distribution and concentrations of by-products. These metabolites, in turn, control the H2 production during the PF. Predominant microbial population for both processes (DF: C/N = 34 Acetobacter lovaniensis, Clostridium butyricum; C/N = 39 C. butyricum, Enterobacter sp, Bifidobacterium; C/N = 82 Lactobacillus casei; PF: Rhodopseudomonas palustris) were in accordance with the final metabolic products.

Accelerated two-stage bioprocess for hydrogen and methane production from palm oil mill effluent using continuous stirred tank reactor and microbial electrolysis cell

This paper investigates the production of hydrogen (H2) and methane (CH4) from palm oil mill effluent (POME) using an integrated approach of thermophilic continuous stirred tank reactor (CSTR) and mesophilic microbial electrolysis cell (MECs). CSTR reactor was operated at pH 5.5, 80 rpm, 2 days HRT, 60 g COD L-1 d-1 organic loading rate (OLR) and 55 °C temperature with the given hydrogen yield of 205 ml H2 gCOD-1 along with acetic, butyric, propionic, and lactic acid as by-products. Continuous, single-chambered MECs fed with dark fermentation effluents were operated at an applied voltage of 0.5 V at 37 °C to obtain methane yield and production rate (MPR) of 290 ml CH4 gCOD-1 and 2700 ml CH4 L-1 at 8 days of hydraulic retention times (HRT). The overall process led to total energy recovery of 92.72% with 91% COD removal efficiency. Microbial community analysis reveals Thermoanerobacterium sp dominated in CSTR whereas exoelectrogens of Methanobacterium formicicum and Methanobacterium beijingense were found to be the chief dominant microbial species on anodic electrode of MECs.

Dark fermentation effluent as substrate for hydrogen production from Rhodobacter capsulatus highlighting the performance of different fermentation systems.

Hydrogen production by biological route is a potentially sustainable alternative. Nowadays, energy production from sustainable sources has become urgent for several countries as well as for international policies. In this perspective, hydrogen has gained substantial global attention as clean, sustainable, and versatile energy carrier. In the current work, the resulting effluent from dark fermentation, rich in organic acids, was used as substrate for the purple non-sulfur bacteria (PNS) Rhodobacter capsulatus. In the first stage, experiments were carried out in bioreactors of 50mL to check the influence of the composition of the effluent dark fermentation. The results proved that the provision of a sugar source improved bio-H2 production. The lactose and lactic acid concentrations exceeding 4.4 and 12g/L, respectively, resulted in a productivity of up to 37.14mmol H2/Ldays. Based on initial conditions obtained on the previous assays, in the second stage, a photo-fermentation in enlarged scale (1.5L) was performed with the purpose to monitor the production of hydrogen and metabolites, sugar consumption and growth cells during the process. It was observed that the maximum productivity obtained was 98.23mmol H2/Ldays in 26h of process.

Integration of a dark fermentation effluent in a microalgal-based biorefinery for the production of high-added value omega-3 fatty acids

Dark fermentation is an anaerobic digestion process of biowaste, used to produce hydrogen- for generation of energy- that however releases high amounts of polluting volatile fatty acids, such as acetic acid, in the environment. In order for this biohydrogen production process to become more competitive, the volatile fatty acids stream can be utilized through conversion to high added-value metabolites, such as omega-3 fatty acids. The docosahexaenoic acid is one of the two most known omega-3 fatty acids and has been found to be necessary for a healthy brain and proper cardiovascular function. The main source is currently fish, which obtain the fatty acid from the primary producers, microalgae, through the food chain. Crypthecodinium cohnii, a heterotrophic marine microalga, is known for accumulating high amounts of docosahexaenoic acid, while offering the advantage of assimilating various carbon sources, such as glucose, ethanol, glycerol and acetic acid. The purpose of this work was to examine the ability of a C. cohnii strain to grow on different volatile fatty acids, as well as, on a pretreated dark fermentation effluent and accumulate omega-3. The strain was found to grow well on relatively high concentrations of acetic, butyric or propionic acid as main carbon source in a fed-batch pH-auxostat. Most importantly, C. cohnii totally depleted the organic acid content of an ultra-filtrated dark fermentation effluent after 60 h of fed-batch cultivation, therefore offering a bioprocess not only able to mitigate environmental pollutants, but also to provide a solution for a sustainable energy production process. The accumulated docosahexaenoic acid content was as high as 29.8% (w/w) of total fatty acids.