Frank R. Bengelsdorf | Universität Ulm (original) (raw)

Papers by Frank R. Bengelsdorf

Organic waste such as food leftovers and kitchen waste have high energy potential but are low in ... more Organic waste such as food leftovers and kitchen waste have high energy potential but are low in sustaining structures. Due to fast acidification in these substrates, the biogas-forming process can be easily impaired by accumulation of volatile organic acids. The effect of additional biofilm carriers was investigated in four experimental digesters of 10L volume operated in parallel. The objective was to test the effect of additional supply of natural biofilm carriers to waste substrates low in structural material. Already a very low amendment of plant structures for biofilm formation significantly stabilised methane production compared to control digesters. Application in a full-scale biogas plant utilising food leftovers together with pig manure enabled to increase the organic load and energy output. INTRODUCTION

The resident microbiota was analyzed in a mesophilic, agricultural biogas plant supplied with foo... more The resident microbiota was analyzed in a mesophilic, agricultural biogas plant supplied with food left-overs, stale bread, pig slurry, potato peelings, and wastes from corn in variable compositions. The dominating bacterial, archaeal, and fungal community members were characterized by a 16S rDNA and 18S rDNA clone library approach. The bacterial microbiota in the biogas plant was quite diverse and dominated by the phylum Firmicutes with representatives from families such as Clostridiaceae , Erysipelotrichaceae , and Ruminococcaceae . Also, the phyla Chloroflexi and Bacteroidetes were present represented by the families Anaerolinaceae and Porphyromonadaceae . The diversity of methanogenic archaea was low, with Methanoculleus and Methanosarcina as dominating genera. Dominating fungi present in the biogas plant were Saccharomyces and Mucor. Denaturating gradient gel electrophoresis was used to compare the molecular 16S- or 18S rDNA fingerprints of the bacterial, archaeal, and fungal c...

Genome Announcements, 2015

Here, we report the draft genome sequence of Clostridium cylindrosporum HC-1, a purine-and glycin... more Here, we report the draft genome sequence of Clostridium cylindrosporum HC-1, a purine-and glycine-fermenting anaerobe, which uses selenoprotein glycine reductase for substrate degradation. The genome consists of a single chromosome (2.72 Mb) and a circular plasmid (14.4 kb).

The effect of additional biofilm carriers on process stability and biogas yield was investigated ... more The effect of additional biofilm carriers on process stability and biogas yield was investigated in different studies (Bengelsdorf et al., submitted; Kazda et al., 2013; Langer et al., 2013). The main focus of these studies was the improvement of the anaerobic digestion process supplied with food leftovers or organic waste as substrate. Food leftovers or dissolved air flotation (DAF) sludge have high energy potential but are low in structural compounds and if supplied, the biogas-forming process is often impaired by accumulation of volatile organic acids. The biofilm mode of life offers advantages as syntrophic interactions due to the physical vicinity of microorganisms within biofilms. Syntrophism is a special case of cooperation between two metabolically different types of microorganisms, which depend on each other for degradation of a certain substrate, typically through transferal of one or more metabolic intermediate(s) between the partners. Due to syntrophic interactions, the ...

Here, we report the complete genome sequence of Moorella thermoacetica DSM 2955T, an acetogenic b... more Here, we report the complete genome sequence of Moorella thermoacetica DSM 2955T, an acetogenic bacterium, which uses the Wood–LjungdahlpathwayforreductionofH2CO2orCO.Thegenomeconsistsofasinglecircularchromosome(2.62Mb).

Biogas from biowaste can be an important source of renewable energy, but the fermentation process... more Biogas from biowaste can be an important source of renewable energy, but the fermentation
process of low-structure waste is often unstable. The present study uses a full-scale biogas reactor to
test the hypothesis that straw as an additional biofilm carrier will increase methane yield; and this
effect is mirrored in a specific microbial community attached to the straw. Better reactor performance
after addition of straw, at simultaneously higher organic loading rate and specific methane yield
confirmed the hypothesis. The microbial communities on straw as a biofilm carrier and of the liquid
reactor content were investigated using 16S rDNA amplicon sequencing by means of 454
pyrosequencing technology. The results revealed high diversity of the bacterial communities in the
liquid reactor content as well as the biofilms on the straw. The most abundant archaea in all samples
belonged to the genera Methanoculleus and Methanosarcina. Addition of straw resulted in a
significantly different microbial community attached to the biofilm carrier. The bacterium Candidatus
Cloacamonas acidaminovorans and methanogenic archaea of the genus Methanoculleus dominated the
biofilm on straw. Syntrophic interactions between the hydrogenotrophic Methanoculleus sp. and
members of the hydrogen-producing bacterial community within biofilms may explain the improved
methane yield. Thus, straw addition can be used to improve and to stabilize the anaerobic process in
substrates lacking biofilm-supporting structures.

Here, we report the closed genome sequence of Clostridium aceticum, an Rnf- and cytochrome-contai... more Here, we report the closed genome sequence of Clostridium aceticum, an Rnf- and cytochrome-containing autotrophic acetogen that is able to convert CO2 and H2 to acetate using the Wood-Ljungdahl pathway. The genome consists of a circular chromosome (4.2 Mbp) and a small circular plasmid (5.7 kbp).

Numerous observations indicate a high flexibility of microbial communities in different biogas re... more Numerous observations indicate a high flexibility of microbial communities in different biogas reactors during anaerobic digestion. Here, we describe the functional redundancy and structural changes of involved microbial communities in four lab-scale continuously stirred tank reactors (CSTRs, 39°C, 12 L volume) supplied with different mixtures of maize silage (MS) and sugar beet silage (SBS) over 80 days. Continuously stirred tank reactors were fed with mixtures of MS and SBS in volatile solid ratios of 1:0 (Continuous Fermenter (CF) 1), 6:1 (CF2), 3:1 (CF3), 1:3 (CF4) with equal organic loading rates (OLR 1.25 kgVS m−3 d−1) and showed similar biogas production rates in all reactors. The compositions of bacterial and archaeal communities were analysed by 454 amplicon sequencing approach based on 16S rRNA genes. Both bacterial and archaeal communities shifted with increasing amounts of SBS. Especially pronounced were changes in the archaeal composition towards Methanosarcina with increasing proportion of SBS, while Methanosaeta declined simultaneously. Compositional shifts within the microbial communities did not influence the respective biogas production rates indicating that these communities adapted to environmental conditions induced by different feedstock mixtures. The diverse microbial communities optimized their metabolism in a way that ensured efficient biogas production.

This study aimed at the investigation of the mechanisms of acidogenesis, which is a key process d... more This study aimed at the investigation of the mechanisms of acidogenesis, which is a key process during anaerobic digestion. To expose possible bottlenecks, specific activities of the key enzymes of acidification, such as acetate kinase (Ack, 0.23–0.99 U mg−1 protein), butyrate kinase (Buk, < 0.03 U mg−1 protein) and butyryl-CoA:acetate-CoA transferase (But, 3.247.64 U mg−1 protein), were determined in cell free extracts of biogas reactor content from three different biogas reactors. Furthermore, the detection of Ack was successful via Western blot analysis. Quantification of corresponding functional genes encoding Buk (buk) and But (but) was not feasible, although an amplification was possible. Thus, phylogenetic trees were constructed based on respective gene fragments. Four new clades of possible butyrateproducing bacteria were postulated, as well as bacteria of the genera Roseburia or Clostridium identified. The low Buk activity was in contrast to the high specific But activity in the analysed samples. Butyrate formation via Buk activity does barely occur in the investigated biogas reactor. Specific enzyme activities (Ack, Buk and But) in samples drawn from three different biogas reactors correlated with ammonia and ammoniumconcentrations (NH3 and NH4+-N), and a negative dependency can be postulated. Thus, high concentrations of NH3 and NH4+-N may lead to a bottleneck in acidogenesis due to decreased specific acidogenic enzyme activities.

Background Large amounts of fibre-rich organic waste material from public green and private gard... more Background
Large amounts of fibre-rich organic waste material from public green and private gardens have to be treated environmentally friendly; however, this fibre-rich biomass has low biogas yields. This study investigated the presence of fungi in full-scale biogas plants as well as in laboratory reactors and elucidated the importance of fungi for the biogas process.

Methods
The dominating members of the eukaryotic community were identified by analyzing 18S rRNA gene and internal transcribed spacer 1 (ITS1) region fragments of clone libraries. These identifications were accompanied by diverse microscopic techniques such as fluorescence microscopy and conventional scanning electron microscopy.

Results
Cells of presumably fungal origin were characterized by intensive fluorescence and were about 1 order of magnitude larger than prokaryotic cells. Molecular techniques enabled to identify fungi from the subphyla Agaricomycotina, Mucoromycotina, Pezizomycotina, Pucciniomycotina and Saccharomycotina and from the class Neocallimastigomycetes. Members of these groups can be important for microbial degradation of complex compounds, due to the ability to penetrate cell walls, and thus open the cells for the influx of bacteria, further enhancing degradation.

Conclusions
Optimal treatment of biowaste depends on the amount of lignocelluloses. Targeted application of fungi to the biogas process will open wider possibilities for anaerobic treatment of fibre-rich biomass and can result in better biomass utilization as a renewable energy resource. Due to higher temperature optima of fungal cellulolytic enzymes, the thermophilic process is suggested for anaerobic degradation of fibre-rich biomass.

""The resident microbiota was analyzed in a mesophilic, continuously operating biogas plant pred... more ""The resident microbiota was analyzed in a mesophilic, continuously operating
biogas plant predominantly utilizing food residues, stale bread, and other waste
cosubstrates together with pig manure and maize silage. The dominating bacterial,
archaeal, and eukaryotic community members were characterized by two
different 16S/18S rRNA gene culture-independent approaches. Prokaryotic 16S
rRNA gene and eukaryotic 18S rRNA gene clone libraries were constructed and
further analyzed by restriction fragment length polymorphism (RFLP), 16S/18S
rRNA gene sequencing, and phylogenetic tree reconstruction. The most dominant
bacteria belonged to the phyla Bacteriodetes, Chloroflexus, and Firmicutes.
On the family level, the bacterial composition confirmed high differences
among biogas plants studied so fare. In contrast, the methanogenic archaeal
community was similar to that of other studied biogas plants. Furthermore, it
was possible to identify fungi at the genus level, namely Saccharomyces and
Mucor. Both genera, which are important for microbial degradation of complex
compounds, were up to now not found in biogas plants. The results revealed
their long-term presence as indicated by denaturating gradient gel electrophoresis
(DGGE). The DGGE method confirmed that the main members of the
microbial community were constantly present over more than one-year period.""

"Acetogenic bacteria employing the Wood–Ljungdahl pathway can be used as biocatalysts in syngas f... more "Acetogenic bacteria employing the Wood–Ljungdahl pathway can be used as biocatalysts in syngas fermentation for the
production of biofuels such as ethanol or butanol as well as biocommodities such as acetate, lactate, butyrate, 2,3 butanediol,
and acetone. The potential of such processes can be projected by the global syngas output, which was 70,817 megawatts
thermal in 2010 and is expected to increase up to 72% in 2016. To date, different acetogens are used as commercial production
strains for industrial syngas fermentations in pilot or demonstration plants (Coskata, INEOS Bio, LanzaTech) and first
commercial units are expected to launch operation in the near future (INEOS Bio, LanzaTech). Considerations on potential
yields are quite promising for fermentative production. New methods for metabolic engineering were established to construct
novel recombinant acetogenic biocatalysts. Synthetic biology will certainly play a major role in constructing strains for
commercial operations. This way, a cheap and abundant carbon source most probably replace, processes based on crude oil
or sugar in the near future."

Biofilm-based reactors are effectively used for wastewater treatment but are not common in biogas... more Biofilm-based reactors are effectively used for wastewater treatment but are not common in biogas
production. This study investigated biofilm dynamics on biofilm carriers incubated in batch biogas reactors
at high and low organic loading rates for sludge from meat industry dissolved air flotation units.
Biofilm formation and dynamics were studied using various microscopic techniques. Resulting micrographs
were analysed for total cell numbers, thickness of biofilms, biofilm-covered surface area, and the
area covered by extracellular polymeric substances (EPS).
Cell numbers within biofilms (1011 cells ml1) were up to one order of magnitude higher compared to
the numbers of cells in the fluid reactor content. Further, biofilm formation and structure mainly
correlated with the numbers of microorganisms present in the fluid reactor content and the organic
loading. At high organic loading (45 kg VS m3), the thickness of the continuous biofilm layer ranged
from 5 to 160 mm with an average of 51 mm and a median of 26 mm. Conversely, at lower organic loading
(15 kg VS m3), only microcolonies were detectable. Those microcolonies increased in their frequency of
occurrence during ongoing fermentation. Independently from the organic loading rate, biofilms were
embedded completely in EPS within seven days. The maturation and maintenance of biofilms changed
during the batch fermentation due to decreasing substrate availability. Concomitant, detachment of
microorganisms within biofilms was observed simultaneously with the decrease of biogas formation.
This study demonstrates that biofilms of high cell densities can enhance digestion of organic waste and
have positive effects on biogas production.

"Organic waste accrues as liquid and solid material which requires different treatment in anaero... more "Organic waste accrues as liquid and solid material
which requires different treatment in anaerobic digestion
plants. Food leftovers, such as kitchen waste have high
energy potential but are low in structural compounds and
the biogas-forming process is often impaired by accumulation
of volatile organic acids. The effect of additional
biofilm carriers on process stability and biogas yield was
tested in two of four parallel operating experimental digesters
of 9L volume. It has been found that slight amendment
of plant structures for biofilm formation significantly
stabilised methane production compared to control digesters.
Anaerobic treatment of municipal solid waste (MSW)
can be done in garage-shaped fermentation containers.
The efficiency of the degradation of volatile solids (VS)
and potential methane yield was evaluated using fermentation
bags in a full-scale biogas plant. The results showed
levels of VS degradation of the studied MSW above
50 %. Both experimental approaches have demonstrated
that organic waste can be a valuable source of regenerative
energy when appropriate technology is applied."

PhD Thesis by Frank R. Bengelsdorf

A mesophilic, continually operating, agricultural biogas plant utilizing predominantly biowaste w... more A mesophilic, continually operating, agricultural biogas plant utilizing predominantly biowaste was analyzed with respect to the composition and diversity of the microbial community as well as the stability of the microbial community over time by molecular methods. Therefore, different clone libraries containing specific DNA fragments were constructed. The bacterial community was dominated by the phyla Bacteroidetes, Firmicutes and Chloroflexi, and was composed of the bacterial families Clostridiaceae, Caldilineaceae, and Porphyromonadaceae. Methylotrophic bacteria were detected by the functional gene mxaF. Remarkably, the genus Methylocaldum is in the literature described as methantroph. The methanogenic archaeal community was dominated by the genus Methanoculleus. The current study provides the first report of the detection of fungal 18S rDNA sequences in biogas reactor content. Genera such as Saccharomyces and Mucor could be described.
DGGE was used to monitor the bacterial and archaeal 16S rDNA as well as the eukaryotic 18S rDNA composition and showed a stable microbial community over a 15-months period.
Fluorescence microscopy analyses were done to determine the total cell count (1.46 (± 0.3)× 1010 cells ml-1) using stained cells and to detect methanogenic archaeal cells (3.5 (± 0.78)× 108 cells ml-1) using their native coenzyme F420 autofluorescence.
Substrates such as biowaste possess low structure and provide a high energy potential if supplied to a biogas reactor. To stabilize a biogas-forming process at higher organic loading rates, straw was added to the biogas reactor to provide surfaces for microorganisms to form biofilms. With respect to the hypothesis, evidence was found for a higher abundance of a syntrophic bacterium, Candidatus Cloacamonas acidaminovorans, living in the biofilm on straw. It seems that this organism undergoes some kind of syntrophic interaction with the predominating hydrogenotrophic methanogenic archaea of the genus Methanocullus.

Genome Announcements, 2015