Two-phase Anaerobic Fermentation Research Articles

Regulation of hydraulic retention time on caproic acid production via two-phase anaerobic fermentation of Chinese cabbage waste with autopoietic electron donors

The effects of hydraulic retention time (HRT) on the performance of two-phase anaerobic fermentation for caproic acid production from Chinese cabbage waste (CCW) were investigated. In the electron donor phase, yeast was inoculated to achieve efficient autopoietic ethanol, providing electron donors for the chain elongation process. Shorter HRT led to drastic fluctuations in microorganisms, thus resulting in lower acid yields at HRT of 6 days. At HRT of 10 days, the balanced collaboration of various key bacteria avoided the accumulation of intermediate by-products, and the caproic acid production reached 4660 mg COD/L, which was 119.5% and 154.8% higher than that at HRTs of 6 and 14 days, respectively. At HRT of 14 days, the low ethanol loading rate resulted in ethanol excessive-oxidation to acetic acid. Acetic acid accounted for 41.5% of the total product, while the selectivity of caproic acid was only 15.3%. The main contributor to the production process of caproic acid was Caproiciproducens, while the Ruminalococcaceae also played a role in the process. This study provided a theoretical basis for the efficient production of caproic acid through continuous fermentation with autopoietic electron donors.

The colon microcosm: a novel in vitro model to study Candida albicans colonisation of the human colon

Candida albicans colonises the gastro-intestinal (GI) tract of over 60% of the population. In severely ill or immune compromised patients, this fungus can escape the gut, disseminate through the body and cause systemic disease. Most research in the field has focused on defining traits that contribute directly to virulence; there are comparatively few studies which have addressed how C. albicans colonises and persists in the gut. Furthermore, such studies have typically been performed mouse models devoid of resident GI bacteria, completely neglecting the major impact of the local microbiota on GI colonisation. How, then, does C. albicans persist in the GI tract in the presence of the normal gut microbiota? To address this question, a novel in vitro two-phase anaerobic fermentation system that simulates the human colon microenvironment has been developed. This “colon microcosm” supports the growth of human faecal microbiota in liquid anaerobic colon medium (phase 1) and C. albicans growth on agar plugs which are added to the medium to mimic the epithelial surface (phase 2). The impact of C. albicans upon the faecal microbiota is monitored by examining the planktonic phase (phase 1), whilst the effect of the microbiota on the growth of C. albicans is monitored after extracting C. albicans cells from the agar plugs (phase 2). The results of assays carried out to validate the model will be presented, as will data from pilot studies which illustrate the potentially exploitable impact of the human GI microbiota from healthy individuals on C. albicans growth.

Enhancement of enzyme activities and VFA conversion by adding Fe/C in two-phase high-solid digestion of food waste: Performance and microbial community structure

Two-phase high-solid digestion is conducive to the degradation of food waste. In this study, Fe/C was added in high-solid digestion in different acidification and/or methanogenic phase. The experimental results indicated that it significantly increased the cumulative yield of biomethane. When Fe/C was added to the acidification phase only and both the acidification and methanogenic phases, the biomethane yield reached 474.07 ± 7.03 and 475.47 ± 4.68 mL·g VS −1, respectively, and the biodegradation rate reached 87.30% and 87.58%, respectively, indicating that Fe/C had mainly effect on the performance of acidification phase. In a two-phase anaerobic fermentation system, the activity of dehydrogenases and the concentration of coenzyme F420 were 2.23–2.95 mg·g−1·h−1 and 0.0063–0.0294 mol·g−1 volatile solids, respectively. Additionally, the archaeal communities production pathway of methane from using acetic acid to using hydrogen as the reactant.

Study on the effect of stepwise warming on two-phase anaerobic fermentation of cow manure

In order to explore the influence of different stepwise heating methods for the acid-producing phase on the gas production of the methane-producing phase, the stepwise heating method with the best acidification, the highest gas production and the best energy-saving effect was obtained. Using cow dung as the raw material, the acid-producing phase is used for stepwise warming, the temperature increase range is 20–35 °C, set three different step-by-step heating methods respectively: the first group is heated by 5 °C/2 d, and the second group is heated by 2.5 °C/d; the third group was heated by 2 °C, 8 °C and 5 °C respectively once every other day; constant temperature fermentation after heating to 35 °C; and a set of acid-producing phase constant temperature 35 °C fermentation; the methane-producing phase is always fermented at a constant temperature of 38 °C; analyze the changes of different parameters. The results show that, in the first group, the total mass concentration of volatile fatty acids is 9372.46 mg/L; the proportion of the total concentration of acetic acid butyric acid to the mass concentration of volatile fatty acids is 77 %; the cumulative gas production volume is 6253 mL, and the cumulative methane production volume is 3741 mL, the total energy consumption is 638.32 kJ, and the heat generated by biogas combustion is 156.33 kJ; the difference between system energy consumption and production capacity is 481.99 kJ. As for the second group, the total mass concentration of volatile fatty acids is 7810.49 mg/L, and the proportion of the total concentration of acetic acid butyric acid to the mass concentration of volatile fatty acids is 74 %. The cumulative gas production volume is 4583 mL, and the cumulative methane production volume is 2521 mL. The total energy consumption is 629.46 kJ, and the heat generated by biogas combustion is 114.58 kJ. Moreover, the difference between system energy consumption and production capacity is 514.88 kJ. In the third group, the total mass concentration of volatile fatty acids is 7664.71 mg/L, the proportion of the total concentration of acetic acid butyric acid to the mass concentration of volatile fatty acids is 75 %; the cumulative gas production volume is 4606 mL, the cumulative methane production volume is 2579 mL. The total energy consumption is 624.18 kJ, and the heat generated by biogas combustion is 115.15 kJ. The difference between system energy consumption and production capacity is 509.03 kJ. In the constant temperature 35 °C group, by contrast, the cumulative gas production volume is 6565 mL, the cumulative methane production volume is 3939 mL. The total energy consumption is 765.74 kJ, and the heat generated by biogas combustion is 164.13 kJ. The difference between system energy consumption and production capacity is 601.61 kJ. According to the comparative analysis of the three groups, the first group has the best acidification effect and highest gas production, and the difference in energy consumption compared with the constant temperature group is also lower, which is more economical. Therefore, the step-by-step heating method of 5 °C/2 d is the best.

Efficiency of Two-Phase Anaerobic Fermentation and the Physicochemical Properties of the Organic Fraction of Municipal Solid Waste Processed in a Vortex-Layer Apparatus

Pretreatment of the organic fraction of municipal solid waste (OFMSW) is a necessary step to accelerate the process of anaerobic digestion in order to avoid rapid acidification and inhibition of methanogenesis. This work shows for the first time the effect of pretreatment in a vortex-layer apparatus (VLA) on the physicochemical properties and characteristics of the anaerobic thermophilic, two-phase fermentation of OFMSW. Pretreatment in a VLA led to a decrease in the amount of fat, an increase in pH, a slight increase in the amount of protein in dry matter, and a change in the density and dry matter content. OFMSW processing in a VLA for 2 min increased the specific yield of biogas and methane by 11.6 and 15.8%, respectively.

Comparison of bio-hydrogen and bio-methane production performance in continuous two-phase anaerobic fermentation system between co-digestion and digestate recirculation

The effect of co-digestion of food waste (FW) and cow dung (CD) with different ratios, and digestate recirculation with different recirculation ratios (RR) on the substrate degradation and energy production in continuous two-stage anaerobic fermentation system was investigated. Results from experiments indicated that co-digestion and digestate recirculation could promote the hydrogen production rate (HPR) and the methane production rate (MPR). Maximum HPR and MPR of 3.3 and 3.1 L/L/d were achieved for two-stage fermentation with recirculation system at RR of 0.4. Meanwhile, both co-digestion and digestate recirculation technology could reduce the amount of alkali addition to maintain pH in the hydrogen-reactor. Compared to digestate recirculation, co-digestion of FW and CD promote much more energy production, 654.9 and 4854.8 kJ/kgVSr were obtained from the co-digestion of FW and CD with the ratio of 2:1 in the hydrogen reactor and the methane reactor.

Anaerobic hydrogen and methane production from low-strength beverage wastewater

In this study, the low-strength effluent from an equalization tank of the wastewater treatment plant in a beverage factory was used for the production of hydrogen and methane. The COD concentration of this low-strength wastewater was 2.9 ± 2.0 g COD/L. In a two-phase anaerobic fermentation system, the hydrogen-producing bioreactor was operated at HRT 8 h, while the methane-producing reactor operated at HRT 24 h. The maximum MPR, methane yield (MY), methane content and COD removal were 72 ± 31 mL/L-d, 58 ± 12 mL/g COD, 92 ± 2% and 78%, respectively. Energy efficiency in this study was calculated as follows, the maximum heating value was 2.2 × 108 kcal/y. The annual carbon-emission reduction was 8.8 × 104 kg CO2/y, 5.2 × 104 kg CO2/y, 7.2 × 104 kg CO2/y when energy-equivalent coal, natural gas or fuel was used, respectively.

Volatile fatty acid (VFA) and methane generation from sewage sludge and banana straw: influence of pH and two-phase anaerobic fermentation

Volatile fatty acid (VFA) and methane generation from sewage sludge and banana straw: influence of pH and two-phase anaerobic fermentation

Microorganism population in two-phase anaerobic fermentation of separated liquid of dairy manure

In order to reduce incomplete fermentation caused by high substrate viscosity and low mass transfer efficiency during fermentation process, batch and two-phase anaerobic fermentation experiments were conducted in this study. Dairy manure was separated by using solid-liquid separator firstly. Separated liquid (SL) and diluted dairy manure (DDM) as raw materials were evaluated in terms of gas production performance for both batch and two-phase anaerobic fermentation. The microorganism population was characterized by scanning electron microscope (SEM) and Denaturing Gradient Gel Electrophoresis (DGGE). The results showed that Volatile Solid (VS) methane yield of SL was 124.51 L/kg VS, which was 2.09 times higher than that of DDM (59.50 L/kg VS) in batch anaerobic fermentation. The Bacteroides and Veillonella with higher activity were the majority microorganism population in acidogenic phase, whereas the Firmicutes and Corynebacterium with methanogenic properties became the predominant microorganism population in methanogenic phase. This study achieved the phase separation and improved the gas production performance. Keywords: separated liquid, diluted dairy manure, two-phase anaerobic fermentation, microorganism, scanning electron microscope (SEM), Denaturing Gradient Gel Electrophoresis (DGGE) DOI: 10.25165/j.ijabe.20181101.3206 Citation: Li Q, Guan Z J, Zheng G X. Microorganism population in two-phase anaerobic fermentation of separated liquid of dairy manure. Int J Agric & Biol Eng, 2018; 11(1): 206–211.

Microorganism population in two-phase anaerobic fermentation of separated liquid of dairy manure

Microorganism population in two-phase anaerobic fermentation of separated liquid of dairy manure

Improvement in energy recovery by dark fermentative biohydrogen followed by biobutanol production process using obligate anaerobes

Bioenergy generation processes are getting importance due to the utilization of fossil fuels which are exhaustible. The aim of the present study was to enhance the overall energy recovery from substrates through two-phase anaerobic dark fermentation process with obligate anaerobes, Clostridium acetobutylicum MTCC 11274 and Clostridium saccharoperbutylacetonicum DSM 14923. The two-phase (biohydrogen and biobutanol) batch process was carried out under mesophilic condition. Maximum cumulative hydrogen and butanol contents of 3.110 L L−1 (2.48 moL H2 mol−1 glucose) and 4.26 g L−1, respectively were obtained after anaerobic fermentation with C. saccharoperbutylacetonicum. This process resulted in a significant increase in energy recovery (75.50%) as compared to the single stage dark fermentation process. Starchy wastewater supplemented with distiller's dried grains with soluble (DDGS) was found to be a more potential feedstock than starchy wastewater alone for this process and a maximum cumulative hydrogen and butanol contents of 3.003 L L−1 and 4.17 g L−1 respectively were obtained with C. saccharoperbutylacetonicum.

Enhancement of Biogas Production in Two-Phase Anaerobic Fermentation System for Lower-Temperature Applications

For the purpose of enhancing the biogas production and operation stability of system at low temperature, a two-phase anaerobic fermentation facility for rural household energy generation was proposed. In this facility, the quantity of the fermented materials could be balanced by controlling the hydraulic retention time, which based on pH of the acidification tank and the fermentation tank. In addition, a portion of the biogas generated could be used to heat the acidification tank and the fermentation tank. Results shows that the optimal daily production rate of biogas for 1 m3 fermentation liquid was about 1.47 L/L d-1 at a mixing ratio of cow: swine: chicken manure was 3: 1: 0.5. The production rate obtained in this study was more than four times higher than that from traditional single-phase processes (0.35 L/L d-1). About 5.43 m3 biogas can be produced daily per household with an average CH4 content of 76.8%. The two-phase process developed in this work will also reduce environmental pollution and increase energy production efficiencies.

Research on the Efficiency of Acid-Producing and Gas-Producing Based on the Enhancement of High-Performance Composite Strains

A batch test was carried out to investigate the effect of acid-producing fermentative characteristic of a new complex strains LZF-12 with high lignocellulose-degradation ability, which straw was the only carbon source in acidogenic phase. Simultaneity, the biogas-producing performance was also researched by shifting the liquid end products from acidongenic phase to methane phase, which fermentative substrate was the mixture of cow dung and kitchen waste. The results indicated that major fermentation products of acidogenic phase was acetic acid accounted for 70% of total volatile acid, which would be in favor of microorganisms growth of methanogenic phase. In two-phase anaerobic fermentation system, the straw degradation rate of composite strains LZF-12 reached the maximum at 72 hour, among which the degradation rate of cellulose, hemicellulose and lignin reached 55%, 67% and 13% respectively. The methane percentage of biogas-producing phase was more than 50% and 134.7mL/g VS of methane production rate was obtained.

Simultaneous coproduction of hydrogen and methane from sugary wastewater by an “ACSTRH–UASBMet” system

A two-phase “ACSTRH–UASBMet” system has been investigated at the stepwise decreased HRT for the simultaneous production of hydrogen and methane in this study. Hydrogen could be continuously produced from the two-phase hydrogen fermentation of sugary wastewater in ACSTR and effluents from hydrogen fermentation were converted into methane in UASB reactor. At optimum conditions (HRTH: 5 h, HRTMet: 15 h), the highest hydrogen production rate of 5.69 (±0.06) mmol L−1 h−1 was obtained from sugary wastewater and methane was continuously produced from effluents of hydrogen fermentation with a production rate of 3.74 (±0.13) mmol L−1 h−1. The total bioenergy recovery by coproduction of hydrogen and methane from sugary wastewater reached 19.37 W and a total of 92.41% of substrate was converted to the biogas (hydrogen and methane) with two-phase anaerobic fermentation.

Parameters Optimization of Two-Phase United Anaerobic Fermentation Hydrogen-Methane Production

The two-phase united anaerobic fermentation has been paid more and more attention in recent years. But how to increase the biogas production yield and the degradation rate of organic matter needs more research. The batch anaerobic fermentation studies demonstrated the feasibility of H2 and CH4 generation utilizing kitchen wastewater as substrate, and the vaccination rate, dilution rate, substrate concentration were optimized. The conclusion showed that dilution rate is the most important factor, following by kitchen wastewater concentration and inoculum volume. The most excellent program of the organic load, the inoculation volume and the dilution volume are 150 +300 ml, 135 ml, 225 ml, respectively. Under these conditions the hydrogen and methane production rate were the highest of 4.15 ml/ml，2.55 ml/ml (calculated as the wastewater volume), respectively. The acid-forming pathways of kitchen wastewater was typical butyric- propionic acid mixed fermentation type. The appropriate dilution could decrease the concentration of the total acids and increase the biogas production yield.

Cogeneration of hydrogen and methane from protein-mixed food waste by two-phase anaerobic process

The cogeneration of hydrogen and methane from protein-mixed food waste by two-phase anaerobic fermentation was investigated for the first time in this paper. The hydrogen-producing bacteria derived from activated sludge were used to produce hydrogen from defatted milk powder (DMP) in the first stage, and Saccharomyces cerevisiae was used to promote the hydrogen production. The hydrogen yield from DMP with S. cerevisiae is promoted from 171.9 ml/g-TVS to 186.1 ml/g-TVS, while the peak hydrogen rate is promoted from 47.9 ml/h to 81.3 ml/h. The residual solutions from the first H 2-producing stage were reutilized by methanogen community to further produce methane in the second stage. Over 96 wt % of acetic acid and butyric acid in the residual solution from DMP with S. cerevisiae are reutilized to give a methane yield of 209.7 ml/g-TVS and peak methane rate of 411.7 ml/d. The cogeneration of hydrogen and methane from DMP markedly increases the energy conversion efficiency from 10.85–11.75% in only hydrogen production to 55.58–61.96%. Because lactose in DMP cogenerates hydrogen yield of 236.5 ml/g-TVS and methane yield of 263.7 ml/g-TVS, it is concluded that lactoprotein in DMP cogenerates hydrogen yield of 136.5 ml/g-TVS and methane yield of 157.8 ml/g-TVS by two-phase fermentation.

Cogeneration of hydrogen and methane from glucose to improve energy conversion efficiency

In order to reutilize the residual solutions derived from hydrogen production and increase the energy conversion efficiency, a novel process of cogenerating hydrogen and methane from glucose using a two-phase anaerobic fermentation process was proposed and investigated. The effects of substrate concentration, weight ratio of inoculation to substrate, pH value and nutrient medium on hydrogen production were studied. The maximum specific hydrogen yield is 2.75 mol H 2/mol glucose when the initial glucose concentration is 1%, the weight ratio of inoculation to substrate is 2:1 and the pH value is 6. The residual solutions derived from hydrogen production were reused to produce methane by methanogen in another reactor. The maximum specific methane yield is 2.13 mol CH 4/mol glucose when the reutilization rates of ethanol, acetic acid, butyric acid, valeric acid, and caproic acid are all above 90%. The cogeneration process can dramatically increase the energy conversion efficiency from 23% (hydrogen only production) to 82%.

Production of hydrogen and methane from potatoes by two-phase anaerobic fermentation

A two-phase anaerobic process to produce hydrogen and methane from potatoes was investigated. In the first phase, hydrogen was produced using heat-shocked sludge. About 12 h lag-phase vanished, hydrogen yield increased from 200.4 ml/g-TVS to 217.5 ml/g-TVS and the maximum specific hydrogen production rate also increased from 703.4 ml/g-VSS d to 800.5 ml/g-VSS d when improved substrate was used, in which Cl − was substituted for SO 4 2 - . Better performances of 271.2 ml-H 2/g-TVS and 944.7 ml-H 2/g-VSS d were achieved when potatoes were pretreated by α amylase and glucoamylase. In the second phase, methane was produced from the residual of the first phase using methanogens. The maximum additional methane yield was 157.9 ml/g-TVS and the maximum specific methane production rate was 102.7 ml/g-VSS d. The results showed that the energy efficiency increased from about 20% (hydrogen production process) to about 60%, which indicated the energy efficiency can be improved by combined hydrogen and methane production process.

00/00304 Biogasification of solid wastes by two-phase anaerobic fermentation

00/00304 Biogasification of solid wastes by two-phase anaerobic fermentation

Biogasification of solid wastes by two-phase anaerobic fermentation

Municipal, industrial and agricultural solid wastes, and biomass deposits cause large-scale pollution of land and water. Gaseous products of waste decomposition pollute the air and contribute to global warming. This paper describes the development of a two-phase fermentation system that alleviates methanogenic inhibition encountered with high-solids feeds, accelerates methane fermentation of solid bed, and captures methane (renewable energy) for captive use to reduce global warming. The innovative system consisted of a solid-bed reactor packed with simulated solid waste at a density of 160 kg/m 3 and operated with recirculation of the percolated culture (bioleachate) through the bed. A rapid onset of solids hydrolysis, acidification, denitrification and hydrogen gas formation was observed under these operating conditions. However, these fermentative reactions stopped after about 2.5 months of solid-bed fermentation at which time total volatile fatty acids (VFA) concentration accumulated to 13,000 mg/l (as acetic) at pH 5, and the reactor head-gas consisted of 75% carbon dioxide, 20% nitrogen, 2% hydrogen and 3% methane. The VFA concentration and gas composition remained virtually constant for an additional 2.5 months of solid-bed fermentation indicating inhibition of the hydrolysis–acidification process. Inhibition of acidogenic fermentation was alleviated by moving the bioleachate to a separate methane-phase fermenter, and recycling methanogenic effluents at pH 7.5 to the solid bed. Coupled operation of the two reactors during the following 4.5 months of two-phase fermentation achieved methanogenic conversion of about 30% of the volatile solids (VS) content of the high-solids feed. Process operation was continuing.