Biogas Fermentation Research Articles

The application of biogas fermentation digestate as soil fertilizer

As organic manure is becoming less available, using different materials as soil fertilizers and the application of the inorganic fertilizers raises many questions. Therefore, it is increasingly important to use compost and biogas digestate to improve soil quality. The activity of the microbial communities ensures the fertility of the soil. One of the most important enzymes is dehydrogenase. This enzyme group catalyses the hydrogen transfer in the process of biological oxidation. Our aim was to examine the effect of biogas digestate on dehydrogenase enzyme activity (DHA) in 3 different types of soil. Hungarian standard method was used to evaluate DHA. The applied biogas digestate was obtained from the Kaposvár Sugar Factory of Hungarian Sugar Ltd. The dose is equal to 16,7 m3ha-1 and 533 kg organic matterha-1. The treatment was performed in three different groups of soil: brown forest soil, calcareous chernozem and carbonate meadow soil. The results showed an increase in DHA in all types of soil. DHA values were the highest in case of the carbonate meadow soil, specifically 0.337 mg formazan/1 g soil/24 h immediately after the treatment and 0.410 after 28 days. A critical aspect to consider during the construction of biogas plants is the soil protection agency’s ban on using soil fertilizers during the winter months. Analysis carried out according to the protocol of sewage sludge examination revealed that biofermentate produced during biogas generation does not contain any environmentally harmful components. After the elaboration of a soil protection plan, the recommended way to apply biogas digestate to arable land is via injectors.

Flow velocities and flow profiles in a thoroughly mixed biogas fermenter

Das Durchmischen von Garsubstrat mittels mechanischer Ruhrwerke ist einer der wichtigsten Prozesse in der Biogasproduktion, jedoch mit hohen Energieeintragen und damit fur den Biogasanlagenbetreiber mit hohen Kosten verbunden. Die Optimierung von Ruhrwerken sowie des Ruhrmanagements gewinnt in den vergangenen Jahren immer mehr an Bedeutung. Zahlreiche wissenschaftliche Studien versuchen mittels Simulationen und Versuchen im Labormasstab Rheologie, Biologie und Stromungsgeschwindigkeiten im Fermenter zu untersuchen und zu beschreiben. Die Ergebnisse zeigen jedoch im Vergleich von Labor- und Praxisuntersuchungen noch erhebliche Abweichungen. Daher wurden mittels magnetisch-induktivem Messsystem die Stromungsgeschwindigkeiten an verschiedenen Stellen des Fermenters bei unterschiedlichen Trockensubstanzgehalten (TS) und Viskositaten des Garsubstrates ermittelt. Bei einem TS-Anstieg von 7,74 auf 10,75 % uber den Versuchszeitraum zeigten die Ergebnisse eine Abnahme der Stromungsgeschwindigkeiten von 8,71 bis 63,77 cm · s-1 auf 0,05 bis 37,36 cm · s-1. Bedingt durch den Anstieg des TS-Gehaltes reduzierten sich die mittleren Stromungsgeschwindigkeiten bei gleicher Ruhrwerkseinstellung um durchschnittlich 70 %. Erganzende Untersuchungen konnten belegen, dass mit einem Anstieg der dynamischen Viskositat die uber die Ruhrwerke induzierten Stromungen am Boden, aber auch an der Oberflache, so gering werden konnen, dass diese messtechnisch nicht mehr erfassbar sind. Diese Arbeit unterstutzt die These, dass es durch Reduktion der Stromungsgeschwindigkeiten zu „Totzonen“ im Fermenter kommen kann.

In-Situ Analysis of Volatile Organic Compounds in Biogas Fermentation Processes Using a Metal Oxide Gas Sensor Array

1. Introduction and Motivation Considering the global climate change, the efficient use of clean and renewable sources of energy is one of the key research areas. In this context, the biological production of methane and other combustible biogas produced by anaerobic fermentation of organic wastes is gaining growing importance. These fermentation processes attract more and more interest mainly due to the possibility to use different types of residues like food waste, dairy wastes and many other organic wastes as feeding substrates. However, efficient biomass conversion to biogas is only possible if the process parameters taking direct influence on the fermentation process are continuously and reliably monitored. This allows efficient process control. One of such key process parameters are the volatile fatty acids (acetic, propionic, butanoic) formed during the biomass conversion process. The reliable monitoring of such organic acids and other volatile organic compounds (VOCs) gives valuable information and their analysis even at low concentrations (<2000 ppm) allows to model the actual microbial state and to adapt the feeding to keep their concentration and their inhibiting influence on the fermentation process low.Conventionally, the analysis of the organic acid composition in anaerobic fermentation processes is done by sophisticated methods like gas chromatography [1], infrared spectroscopy [2], and high pressure liquid chromatography (HPLC) [3]. However, the major disadvantages of these methods are their complicated and time consuming sample pre-treatment routines and high costs.In this paper, an automated measuring system developed by combining a silicon rubber membrane based carrier gas probe (Fig. 1) with a thermo-cyclically operated metal oxide gas sensor array [4] is introduced. This automated system might enable in-situ monitoring of different VOCs developing during the bio-fermentation processes in time periods of about one hour.1. Method of VOC monitoring Metal oxide gas sensors (MOGs) are well established as gas sensing devices for monitoring of VOCs and oxidizable gases like CO, H2 and CH4. Thus, before measurement of dissolved VOCs, CH4 and other to cross-sensitivity contributing gas components present in the biogas fermentation sample must be driven out. In a first step, a small amount of the fermentation liquid (about one liter) is extracted from the main reactor and its pH is shifted to an alkaline value by dosage of potassium hydroxide. This allows transformation of the dissolved organic acids to the dissociated state and enables purging out CH4, H2 and all other non-acidic, physically dissolved gas components contributing to the sensor signal, by a high flow of N2. Then, pH is shifted to a value near or even lower than the pKa value of the organic acids by dosage of phosphorous acid. Now the dissolved organic acids are in the undissociated molecular state and equilibrate with the gas state (Henry´s law). This enables the uptake of molecular dissolved organic acids from the liquid state into the constant flow of synthetic air (carrier gas: 5ml/min) by permeation through the gas permeable silicon rubber membrane of the gas carrier probe. By the help of the carrier gas the organic acids are transported to the metal oxide gas sensor array (Fig 1a) for analysis.1. Results and Discussion Several SnO2/additive gas sensing composites have been prepared and the most interesting candidates with respect to their remarkably high sensitivity and most characteristic conductance vs. time profile (CTP) shapes when operated in thermocyclic mode [4,5] will be reported. When the carrier gas probe is immersed in acetic acid/deionized water admixtures some metal oxides show characteristic CTP-shapes (Fig. 1b) representing the individual surface reaction processes with acetic acid. In addition, some first experiments with real fermentation liquids resulted in some unexpected gas developments with pH and time well indicated by characteristic CTP-changes, which will highlight the presentation.1. Conclusions and outlook By some extended in-situ monitoring experiments of acetic acid in deionized water as a model substance using a gas carrier probe combined with a 4-fold metal oxide sensor array, several metal oxide materials could be identified as good candidates for monitoring of organic acids in biogas fermentation processes.Monitoring experiments in real fermentation samples and analysis of the CTPs yielded gas formation changing with pH and time. These gas formation processes have to be referenced by simultaneous Gas Chromatograph-Mass Spectrometry (GC-MS) analysis and the results will be reported as well in context with the MOG sensitivity data.1. Acknowledgement This work is part of the EBIPREP collaboration project (www.ebiprep.eu/). It is financed by the EU International Programme INTERREG V Oberrhein 2017-2020.

Biogas Fermentation from Vegetable Waste and Horse Rumen Involving Effective Microorganism-4 (EM4)

A vegetable waste is an organic matter that contains cellulose which potential to be processed into biogas with anaerobic fermentation process. The aims of this research are to find out how long time to produce biogas from vegetable waste and horse Rumen by using EM4, what does the effect of the addition of EM4 to the biogas yield and the content of the produced gas. Vegetables waste and Rumen rasio 1:1 (500g:500g). Water Content of 500g. Addition variable of EM4 in each digester are 0 ml, 50 ml, 100 ml, 150 ml dan 200 ml. Fermentation process takes time about 3 to 15 days. This result shows that the average time of fermentation lasts up to 11 days. The addition of 150 ml EM4 generate the highest pressure, come to 322.801 Pa, capable of producing the highest biogas yield of 0.2679 % with CO2content of 5.15 %.

The Analysis Of Biogas Fermentation Time From Cow Manure On Fixed Dome Biodigester Batch Systems

Biogas technology from cow manure in Indonesia has been developing for a long time, but the application of its use as an alternative energy source is not yet widely developed, due to various unknown operations and processes. This research aimed to analyzed of biogas fermentation time in batch system of cow manure. This research used a Fixed Dome type biodigester that had a total volume of 500 litters with its operating system in batches with 80% of the slurry containing cow manure and the rest for the gas chamber. The biogas fermentation time were 5, 10,15,20 25 and 30 days. The raw material from cow manure had an organic COD content of 10.240 mg / l with a pH of 6.7. The C/N feed ratio was set in the condition of 25: 1 and the ratio of slurry of cow manure with water was 1: 1. From the results of the study in batch process, it was found that the longer the fermentation time the higher the methane gas content but the methane gas content decreases on the 30 th day from 59,12% on the 25 th day to 50,04% on the 30 th day of fermentation.

Optimization of an externally mixed biogas plant using a robust CFD method

Biogas plants have to be continuously or periodically mixed to ensure the homogenization of fermenting and fresh substrate. Externally installed mixers provide easier access than submerged mixers but concerns of insufficient mixing deter many operators from using this technology. In this paper, a new approach to improve homogenization of the substrate mixture is proposed by optimizing external mixer configurations across a wide range of rheological properties. Robust optimization of a biogas reactor is coupled with CFD simulations to improve parameters for the angles of inflow and the position of the substrate outlet in a large-scale fermenter. The optimization objective is to minimize the area in the tank which is poorly mixed. We propose to define this ‘‘dead volume zone'' as the region in which the velocity magnitude during mixing falls below a certain threshold. Different dry substance contents are being investigated to account for the varying rheological properties of different substrate compositions. The velocity thresholds are calculated for each dry substance content from the mixer-tank configuration of a real biogas reactor in Brandenburg, Germany (BGA Warsow GmbH & Co. KG). The robust optimization results comprising the whole range of rheological properties are compared to simulations of the original configuration and to optimization results for each individual dry substance content. The robust CFD-based optimized configurations reduce the dead volume zones significantly across all dry substance contents compared to the original configuration. The outcomes of this paper can be particularly useful for plant manufacturers and operators for optimal mixer placement in industrial size biogas fermenters.

An analysis of farmers' resource disposal methods for livestock and poultry waste and their determinants

Based on field research data on farmers in 30 counties (districts) of six cities in Shandong Province, this study systematically examines the methods of disposal of livestock and poultry waste and the factors that influence them, that is, the determinants of farmers’ waste disposal behaviors, using the UTAUT theoretical framework and a disordered multi-class logit model. The results show that, first, economic performance expectancy, subjective norms, farming population, and poultry and livestock breeding numbers have significant effects on the four waste recycling methods considered: direct return, compost fermentation, biogas fermentation, and fresh-packed sale. Second, annual family income has a positive effect on the direct return method. Third, compost fermentation is positively affected by farmers' knowledge, distance from sources of water, and farming scale, and negatively affected by gender and marital status. Fourth, biogas fermentation is negatively affected by the age of farmers and positively affected by the farming income ratio and environmental convenience. Finally, the most important factors affecting the four methods are subjective norms, farming scale, economic performance expectancy, and farming population. Therefore, this study proposes that policies to promote resource utilization of livestock and poultry waste must prioritize raising awareness among the farmers of the advantages of resource disposal of waste; provide reasonable subsidies for waste recycling and enhance policy applicability, pertinence, and motivation; strengthen the promotion of waste recycling technology and improve the practicality of lectures or training content; and improve relevant laws and regulations and enhance authority and usability.

Characteristics and Optimization of Anaerobic Digestion of Tea Waste for Biogas Production

The tea residue from the production of beverage tea is used as anaerobic fermentation biogas production material. The anaerobic fermentation biogas-production experiment is conducted at an intermediate temperature of 35°C, and the biogas potential of the tea residue is reviewed. Using orthogonal experiment method, the effects of temperature, moisture and inoculation rate on the degradation property of tea residue are studied by designing L9 (33) experiment with 3 factors and 3 levels. The primary and secondary review factors and the optimum process conditions are determined. The experimental results show that: the cumulative biogas production after tea residue’s anaerobic fermentation for 40 days is 5270 ml, and the biogas production rate is 658 ml.g-1TS; methane production rate is 227.7 CH4-ml/g-ts. Orthogonal experimental results show that the optimum process conditions are 85% moisture content, 55°C for temperature, and inoculation rate is 20%. The highest TS degradation rate is 45.3%, the VS degradation rate is 61.52%.

Evaluation of methane emission flux from a typical biogas fermentation ecosystem in China

To reduce greenhouse gas emissions and promote sustainable agricultural practices in China, this study used conventional method to examine methane (CH4) production from hydraulic biogas digesters in Jiuxi Town, Yunnan Province, China. The static chamber technique was utilized to measure CH4 emission fluxes from the inlet and outlet of the biogas digesters. For the 100 m3 biogas digester, CH4 emission fluxes from the inlet, outlet, and the biogas digester were 1.043 g/(m2·h), 2.328 g/(m2·h), and 52.669 g/(m3·d); while those for the 8 m3 biogas digester were 0.156 g/(m2·h), 0.083 g/(m2·h), and 23.580 g/(m3·d), respectively. The diurnal and monthly variation of CH4 emission fluxes were further analyzed from the 100 m3 biogas digester. Among the environmental factors, the fermentation temperature and feeding quantity had significant effects on the CH4 emission fluxes. Especially, CH4 leakage from the digesters was evaluated, which would help identify and adjust the methane conversion factor for the typical biogas fermentation ecosystem used in China. For the hydraulic biogas digesters of 8 m3 and 100 m3, the respective leakage ratios were 3.01% and 14.56%. Therefore, it is very important for rural farmers in China to improve the management of household biogas digesters for reducing greenhouse gas emissions.

Effects of magnesium ions in microbial cells adhesion of attached growth system for the enhancement of biogas production

This research aims to improve the biogas production by employing cell immobilisation technique under thermophilic conditions. The thermophilic fermentative biogas production was carried out by immobilising the anaerobic sludge obtained from palm oil mill treatment plant on granular activated carbon (GAC) in repeated batch mode. Different concentration of magnesium ions (Mg2+) (0.25, 0.5, 0.75, 1.0 and 1.5 g/l) on biogas production was investigated at 60°C with an initial sucrose concentration of 5 g/l as feedstock. The effect of Mg2+ supplementation at the initial stage of immobilisation process is important to increase the formation of biofilm in the attached growth system. This study had found that Mg2+ could enhance the biogas production capacity with optimum Mg2+ concentration of 0.75 g/l.

The fertilising potential of manure-based biogas fermentation residues: pelleted vs. liquid digestate

Spreading of manure on agricultural soils is a main source of ammonia emissions and/or nitrate leaching. It has been addressed by the European Union with the Directives 2001/81/EC and 91/676/EEC to protect the environment and the human health. The disposal of manure has therefore become an economic and environmental challenge for farmers. Thus, the conversion of manure via anaerobic digestion in a biogas plant could be a sustainable solution, having the byproducts (solid and liquid digestates) the potential to be used as fertilizers for crops.This work aimed at characterizing and assessing the effect of digestates obtained from a local biogas plant (Biogas Wipptal, Gmbh), either in the form of liquid fraction or as a solid pellet on: (i) the fertility of the soils during an incubation experiment; (ii) the plant growth and nutritional status of different species (maize and cucumber). Moreover, an extensive characterization of the pellet was performed via X-ray microanalytical techniques.The data obtained showed that both digestates exhibit a fertilizing potential for crops, depending on the plant species and the fertilizer dose: the liquid fraction increases the shoot fresh weight at low dose in cucumber, conversely, the solid pellet increases the shoot fresh weight at high dose in maize. The liquid digestate may have the advantage to release nutrients (i.e. nitrogen) more rapidly to plants, but its storage represents the main constraint (i.e. ammonia volatilization). Indeed, pelleting the digestates could improve the storability of the fertilizer besides enhancing plant nutrient availability (i.e. phosphate and potassium), plant biomass and soil biochemical quality (i.e. microbial biomass and activity). The physical structure and chemical composition of pellet digestates allow nutrients to be easily mobilized over time, representing a possible source of mineral nutrients also in long-term applications.

Effect of Fe2+ adding period on the biogas production and microbial community distribution during the dry anaerobic digestion process

Fe2+ is essential for the improvement of biogas production and the growth of anaerobic microorganisms; however, it is often excessively added to anaerobic digesters, leading to the inhibition of biogas production. In this study, the dosing frequency of Fe2+ for the mesophilic and thermophilic biogas fermentation of high-solid swine manure was optimized. The most significant enhancing effect (13.44 %–33.22 %) induced by Fe2+ addition was observed with dosing frequency of 400mg/L for every 5 d, and the maximum efficiency for unit concentration of Fe2+ occurred when the dosing frequency was 400mg/L for every 15 d. Maximum biogas production was obtained in the group with dosing frequency of 400mg/L for every 5 d, and biogas production potential was 465.24mL/(g volatile solid (VS)) based on modified Gompertz predicted model with a maximum rate of 16.72mL/(gVS·d), which was higher than that of the control group (6.78mL/(gVS·d)). In addition, Fe2+ dosing displayed a stimulatory effect on SCOD removal, the SCOD removal with dosing frequency of 400mg/L for every 5 d were highest in all reactors. The optimum dosing frequency of Fe2+ positively affected the microbial community structure. 16S rRNA gene sequencing revealed that the abundances of Firmicutes and Euryarchaeota were increased, which could enhance the hydrolysis-acidification and methanogenesis process during anaerobic digestion process.

Effects of Different Pre-processing Methods on Dry Anaerobic Fermentation of Sugarcane Leaves and Pig Manure

Using agricultural wastes for anaerobic fermentation to produce biogas can not only realize the resource utilization of the wastes, but also prevent the environmental issues caused by straw burning. Sugarcane leaves contain waxy layer, which will cause problems such as difficulty in degradation, long-time fermentation and low biogas production. This paper studies the effects on three pre-processing methods of adding rush rot agent, natural retting for 7 days and water moisture for 24 hours of dry anaerobic fermentation of sugarcane leaves and pig manure. The results show that natural retting for 7 days has the advantage of daily biogas production when the fermentation period is less than 20 days, but this method is not obviously different from that of water moisture for 24 hours. When taking total biogas production volume and volume loading rate as the indicators, water moisture for 24 hours is the best pre-processing method for dry anaerobic fermentation of sugarcane leaves and pig manure when the fermentation period is more than 20 days.

Genome Analyses and Genome-Centered Metatranscriptomics of Methanothermobacter wolfeii Strain SIV6, Isolated from a Thermophilic Production-Scale Biogas Fermenter.

In the thermophilic biogas-producing microbial community, the genus Methanothermobacter was previously described to be frequently abundant. The aim of this study was to establish and analyze the genome sequence of the archaeal strain Methanothermobacter wolfeii SIV6 originating from a thermophilic industrial-scale biogas fermenter and compare it to related reference genomes. The circular chromosome has a size of 1,686,891 bases, featuring a GC content of 48.89%. Comparative analyses considering three completely sequenced Methanothermobacter strains revealed a core genome of 1494 coding sequences and 16 strain specific genes for M. wolfeii SIV6, which include glycosyltransferases and CRISPR/cas associated genes. Moreover, M. wolfeii SIV6 harbors all genes for the hydrogenotrophic methanogenesis pathway and genome-centered metatranscriptomics indicates the high metabolic activity of this strain, with 25.18% of all transcripts per million (TPM) belong to the hydrogenotrophic methanogenesis pathway and 18.02% of these TPM exclusively belonging to the mcr operon. This operon encodes the different subunits of the enzyme methyl-coenzyme M reductase (EC: 2.8.4.1), which catalyzes the final and rate-limiting step during methanogenesis. Finally, fragment recruitment of metagenomic reads from the thermophilic biogas fermenter on the SIV6 genome showed that the strain is abundant (1.2%) within the indigenous microbial community. Detailed analysis of the archaeal isolate M. wolfeii SIV6 indicates its role and function within the microbial community of the thermophilic biogas fermenter, towards a better understanding of the biogas production process and a microbial-based management of this complex process.

Anaerosphaera multitolerans sp. nov., a salt-tolerant member of the family Peptoniphilaceae isolated from a mesophilically operated biogas fermenter fed with maize silage.

In this work, we succeeded in the isolation of a novel species out of a mesophilically operated biogas fermenter fed with maize silage. Strains GS7-6-2T, GS-7K2 and GS-0K3 were isolated from three individual enrichment cultures. 16S rRNA gene sequence comparisons indicated that the isolates had 100 % sequence identity and were most closely related to Anaerosphaera amininiphila WN036T, with which they shared a 16S rRNA gene sequence similarity of 93.1 %. As a representative, strain GS7-6-2T was further characterized. Strain GS7-6-2T was mesophilic with its growth optimum at 30 °C and a pH range from pH 5.5 to 9.5 (optimum, pH 6.0-8.5). Cells were spherical and sometimes arranged into short chains. Growth was possible with up to 3.6 % (w/v) NaCl, but best without additional NaCl. Strain GS7-6-2T produced butyric acid and acetic acid as main fermentation products while growing on GS2 medium. The major cellular fatty acids were C18 : 1ω7c, C16 : 0 and C16 : 1ω9c. The Gram-stain result was negative. The DNA G+C content was 32.8 mol%. Strain GS7-6-2T was able to ferment 16 (comprising four carbohydrates, five amino acids, four organic acids and three nucleotides) out of the 95 tested substrates. Due to the ecological, genetic and phenotypic differences from the most closely affiliated and validly named organism, A. amininiphila WN036T, the isolates represent a novel species within the genus Anaerosphaera, family Peptoniphilaceae, for which the name Anaerosphaera multitolerans sp. nov. is proposed. The type strain is GS7-6-2T (=DSM 107952T=CECT 9705T).

The effect of temperature fluctuation on the microbial diversity and community structure of rural household biogas digesters at Qinghai Plateau.

Seasonal temperature-fluctuation has been regarded as a key environmental factor affecting rural biogas fermentation yields. The present study investigated the impact of seasonal temperature-fluctuation on operating-temperatures and biogas production in rural household digesters at Qinghai Plateau and revealed the related changes in microbial diversity and community structure by 16S rRNA gene high-throughput sequencing (HTS) analysis. Our results showed closely positive correlation between operating-temperatures and biogas production. HTS analysis indicated the highest diversity for bacteria community in autumn (at highest operating-temperatures) and late winter (at lowest operating-temperatures) and for archaea community only in autumn. HTS analysis classified bacteria into 21 phyla and 346 genera with the most predominant phyla Firmicutes, Bacteroidetes and Proteobacteria (> 72.4% in total) and the most predominant genera Proteiniphilum, Clostridium sensustricto 1, Petrimonas, Pseudomonas and Fastidiosipila (37.09-38.61% in total). HTS analysis also revealed two main archaea orders (Methanomicrobiales and Methanobacteriales) and one predominant genus Methanogenium to support plateau biogas fermentation. Especially, a remarkable impact of temperature on the community abundances of bacteria phyla Synergistetes and archaea genera Methanogenium and Thermogymnomonas was observed, and such microbial community structure changes were positively consistent with the biogas production. The present work provided the first set of evidences to link temperature-controlled modulation of microbial community structure with rural household biogas production at Qinghai Plateau.

Hungateiclostridium mesophilum sp. nov., a mesophilic, cellulolytic and spore-forming bacterium isolated from a biogas fermenter fed with maize silage.

In this work, the isolation and characterization of a novel anaerobic, mesophilic and cellulolytic bacterium is described. Comparative analysis of the almost-complete sequence of the 16S rRNA gene showed that the closest relatives were Hungateiclostridium straminisolvens CSK1T (97.53 %) and Hungateiclostridium thermocellum DSM 2360T (95.42 %). Due to physiological and phylogenetic differences from its closest relatives, a new species is proposed. Cells of N2K1T were observed to be rod-shaped, non-motile, spore-forming, Gram-stain-positive and able to adhere directly to cellulose fibre. Cellulolytic activity and optimal growth were observed at 45 °C and neutral pH (optimum, pH 7.5). Of all tested substrates, only filter paper (cellulose) and cellobiose were used for growth. Arabinose, fructose, glucose, lactose, mannitol, mannose, ribose, starch, sucrose, trehalose, xylan and xylose did not support growth. The main fermentation products were acetic acid and isopropanol. The major cellular fatty acids (>5 %) were C16 : 0iso, C16 : 0 DMA and C16 : 0. The type strain, N2K1T, was isolated from a mesophilically operated, lab-scale biogas fermenter fed with maize silage in Freising, Germany in 2017. The genome assembly of strain N2K1T is 4.04 Mbp with a DNA G+C content of 38.36 mol%. The name Hungateiclostridiummesophilum sp. nov. is proposed for the novel organism. Strain N2K1T (=DSM 107956T; =CECT 9704T) represents the type strain of Hungateiclostridiummesophilum sp. nov.

METHODOLOGICAL ASPECTS OF ASSESSING THE STEEL FRAMES RELIABILITY

The peculiarities of biogas technology application in the falling leaves utilization plants are analyzed and the application ofsoil cement is proposed to create the basic elements of such plants. A new schematic and constructive solution of biogasfermenter (bioreactor) with application of soil-cement technology with a blending method for efficient functioning oftechnological chain of biogas fermentation of fallen leaves and other plant residues for energy supply systems has beendeveloped. The possibility of reliable isolation of the space of the bioreactor to the excavation of the pit from the surroundingarray with soil cement screen is substantiated. The corrosion resistance of the soil cement waterproof screen has been proved.

A LAPS-Based Differential Sensor for Parallelized Metabolism Monitoring of Various Bacteria.

Monitoring the cellular metabolism of bacteria in (bio)fermentation processes is crucial to control and steer them, and to prevent undesired disturbances linked to metabolically inactive microorganisms. In this context, cell-based biosensors can play an important role to improve the quality and increase the yield of such processes. This work describes the simultaneous analysis of the metabolic behavior of three different types of bacteria by means of a differential light-addressable potentiometric sensor (LAPS) set-up. The study includes Lactobacillus brevis, Corynebacterium glutamicum, and Escherichia coli, which are often applied in fermentation processes in bioreactors. Differential measurements were carried out to compensate undesirable influences such as sensor signal drift, and pH value variation during the measurements. Furthermore, calibration curves of the cellular metabolism were established as a function of the glucose concentration or cell number variation with all three model microorganisms. In this context, simultaneous (bio)sensing with the multi-organism LAPS-based set-up can open new possibilities for a cost-effective, rapid detection of the extracellular acidification of bacteria on a single sensor chip. It can be applied to evaluate the metabolic response of bacteria populations in a (bio)fermentation process, for instance, in the biogas fermentation process.

Shedding light on biogas: Phototrophic biofilms in anaerobic digesters hold potential for improved biogas production

Conventional anaerobic digesters intended for the production of biogas usually operate in complete darkness. Therefore, little is known about the effect of light on their microbial communities. In the present work, 16S rRNA gene amplicon Nanopore sequencing and shotgun metagenomic sequencing were used to study the taxonomic and functional structure of the microbial community forming a biofilm on the inner wall of a laboratory-scale transparent anaerobic biodigester illuminated with natural sunlight. The biofilm was composed of microorganisms involved in the four metabolic processes needed for biogas production, and it was surprisingly rich in Rhodopseudomonas faecalis, a versatile bacterium able to carry out photoautotrophic metabolism when grown under anaerobic conditions. The results suggested that this bacterium, which is able to fix carbon dioxide, could be considered for use in transparent biogas fermenters in order to contribute to the production of optimized biogas with a higher CH4:CO2 ratio than the biogas produced in regular, opaque digesters. To the best of our knowledge, this is the first study characterising the phototrophic biofilm associated with illuminated bioreactors.