Butyrate is a common fatty acid produced in important fermentative systems, such as the human/animal gut and other H
production systems. Despite its importance, there is little information on the ...partnerships between butyrate producers and other bacteria. The objective of this work was to uncover butyrate-producing microbial communities and possible metabolic routes in a controlled fermentation system aimed at butyrate production. The butyrogenic reactor was operated at 37°C and pH 5.5 with a hydraulic retention time of 31 h and a low hydrogen partial pressure (PH
). High-throughput sequencing and metagenome functional prediction from 16S rRNA data showed that butyrate production pathways and microbial communities were different during batch (closed) and continuous-mode operation.
,
, and
were the most abundant phylotypes in the closed system without PH
control, whereas
,
, and
were the most abundant phylotypes under continuous operation at low PH
. Putative butyrate producers identified in our system were from
,
,
, and
. Metagenome prediction analysis suggests that nonbutyrogenic microorganisms influenced butyrate production by generating butyrate precursors such as acetate, lactate, and succinate. 16S rRNA gene analysis suggested that, in the reactor, a partnership between identified butyrogenic microorganisms and succinate (i.e.,
), acetate (i.e.,
and
), and lactate producers (i.e.,
and
) took place under continuous-flow operation at low PH
.
This study demonstrates how bioinformatics tools, such as metagenome functional prediction from 16S rRNA genes, can help understand biological systems and reveal microbial interactions in controlled systems (e.g., bioreactors). Results obtained from controlled systems are easier to interpret than those from human/animal studies because observed changes may be specifically attributed to the design conditions imposed on the system. Bioinformatics analysis allowed us to identify potential butyrogenic phylotypes and associated butyrate metabolism pathways when we systematically varied the PH
in a carefully controlled fermentation system. Our insights may be adapted to butyrate production studies in biohydrogen systems and gut models, since butyrate is a main product and a crucial fatty acid in human/animal colon health.
Dark fermentation for bio-hydrogen (bio-H₂) production is an easily operated and environmentally friendly technology. However, low bio-H₂ production yield has been reported as its main drawback. Two ...strategies have been followed in the past to improve this fact: genetic modifications and adjusting the reaction conditions. In this paper, the second one is followed to regulate the bio-H₂ release from the reactor. This operating condition alters the metabolic pathways and increased the bio-H₂ production twice. Gas release was forced in the continuous culture to study the equilibrium in the mass transfer between the gaseous and liquid phases. This equilibrium depends on the H₂, CO₂, and volatile fatty acids production. The effect of reducing the bio-H₂ partial pressure (bio-H₂ pp) to enhance bio-H₂ production was evaluated in a 30 L continuous stirred tank reactor. Three bio-H₂ release strategies were followed: uncontrolled, intermittent, and constant. In the so called uncontrolled fermentation, without bio-H₂ pp control, a bio-H₂ molar yield of 1.2 mol/mol glucose was obtained. A sustained low bio-H₂ pp of 0.06 atm increased the bio-H₂ production rate from 16.1 to 108 mL/L/h with a stable bio-H₂ percentage of 55 % (v/v) and a molar yield of 1.9 mol/mol glucose. Biogas release enhanced bio-H₂ production because lower bio-H₂ pp, CO₂ concentration, and reduced volatile fatty acids accumulation prevented the associated inhibitions and bio-H₂ consumption.
Butyrate is a common fatty acid produced in important fermentative systems, such as the human/animal gut and other H 2 production systems. Despite its importance, there is little information on the ...partnerships between butyrate producers and other bacteria. The objective of this work was to uncover butyrateproducing microbial communities and possible metabolic routes in a controlled fermentation system aimed at butyrate production. The butyrogenic reactor was operated at 37°C and pH 5.5 with a hydraulic retention time of 31 h and a low hydrogen partial pressure (PH 2). High-throughput sequencing and metagenome functional prediction from 16S rRNA data showed that butyrate production pathways and microbial communities were different during batch (closed) and continuousmode operation. Lactobacillaceae, Lachnospiraceae, and Enterococcaceae were the most abundant phylotypes in the closed system without PH 2 control, whereas Prevotellaceae, Ruminococcaceae, and Actinomycetaceae were the most abundant phylotypes under continuous operation at low PH 2. Putative butyrate producers identified in our system were from Prevotellaceae, Clostridiaceae, Ruminococcaceae, and Lactobacillaceae. Metagenome prediction analysis suggests that nonbutyrogenic microorganisms influenced butyrate production by generating butyrate precursors such as acetate, lactate, and succinate. 16S rRNA gene analysis suggested that, in the reactor, a partnership between identified butyrogenic microorganisms and succinate (i.e., Actinomycetaceae), acetate (i.e., Ruminococcaceae and Actinomycetaceae), and lactate producers (i.e., Ruminococcaceae and Lactobacillaceae) took place under continuousflow operation at low PH 2. IMPORTANCE This study demonstrates how bioinformatics tools, such as metagenome functional prediction from 16S rRNA genes, can help understand biological systems and reveal microbial interactions in controlled systems (e.g., bioreactors). Results obtained from controlled systems are easier to interpret than those from human/animal studies because observed changes may be specifically attributed to the design conditions imposed on the system. Bioinformatics analysis allowed us to identify potential butyrogenic phylotypes and associated butyrate metabolism pathways when we systematically varied the PH 2 in a carefully controlled fermentation system. Our insights may be adapted to butyrate production studies in biohydrogen systems and gut models, since butyrate is a main product and a crucial fatty acid in human/animal colon health. KEYWORDS butyrate production pathways, PICRUSt, Prevotellaceae, hydrogen partial pressure, interconversion reactions, predicted metagenome functional content F ermentation involves the degradation of organic material by anaerobic microorganisms in an environment with low dissolved oxygen and produces short-chain fatty acids (SCFA) (e.g., butyrate and acetate) and gases, including methane (CH 4),
Dielectric Properties and Relaxation of Bi2Ti2O7 Turner, Christopher G.; Esquivel-Elizondo, J. Roberto; Nino, Juan C.
Journal of the American Ceramic Society,
June 2014, Volume:
97, Issue:
6
Journal Article
Peer reviewed
The dielectric properties of Bi2Ti2O7 were explored as a function of temperature and frequency. A comparison between the dielectric response of the well‐known Bi1.5Zn0.92Nb1.5O6.92 (BZN) pyrochlore ...and the recently available Bi2Ti2O7 sintered ceramic revealed considerable differences, which indicate that chemical disorder, and not atomic displacement on its own, is chiefly responsible for the dielectric relaxation in bismuth pyrochlores. A low‐frequency (<10 kHz) and relatively high‐temperature (~125 K) dielectric relaxation was observed in Bi2Ti2O7. An Arrhenius function was used to model the relaxation behavior and yielded an activation energy of 0.162 eV and an attempt jump frequency of ~1 MHz. This response is consistent with space charge polarization and not the result of dipolar or ionic disorder.
Display omitted
•Microorganisms-based methods for harmful algal blooms (HABs) are discussed.•The use of microbial aggregates shows potential for the control of HABs.•The prospect of genetic ...engineering for controlling HABs is discussed.•An integrative processing of “flocculation-lysis-degradation-nutrients regulation” is proposed to control HABs.
Harmful algal blooms (HABs) are a worldwide problem with numerous negative effects on water systems, which have prompted researchers to study applicable measures to inhibit and control them. This review summarized the current microorganisms-based methods or technologies aimed at controlling HABs. Based on their characteristics, these methods can be divided into two categories: methods based on single-species microorganisms and methods based on microbial aggregates, and four types: methods for rapid decrease of algal cells density (e.g., alga-bacterium and alga-fungus bioflocculation), inhibition of harmful algal growth, lysis of harmful algae (e.g. algicidal bacteria, fungi, and actinomycete), and methods based on microbial aggregates (periphytons and biofilms). An integrative process of “flocculation-lysis-degradation-nutrients regulation” is proposed to control HABs. This review not only offers a systematic understanding of HABs control technologies based on microorganisms but also elicits a re-thinking of HABs control based on microbial aggregates.
•The periphytic EPS were mainly composed of polysaccharides and proteins.•The periphytic EPS showed high turbidity removal capacity.•The periphytic EPS showed efficient aniline blue (AB) removal ...capacity.•The AB removal mechanism was a combined technique of “adsorption-flocculation”.•Periphytic biofilms were good sources for bioflocculants preparation.
The aim of this work was to study the characteristics and flocculating properties of extracellular polymeric substances (EPS) extracted from periphytic biofilms. The periphytic EPS, with an extracted yield of 491.8mg/g, were mainly composed of hetero-polysaccharides and proteins, and the elements C1s, N1s, and O1s. Polysaccharides represented 53.28% of the periphytic EPS. Proteins constituted 20.26% of the EPS, and contributed to at least 34.65% of the total flocculating activity. The periphytic EPS showed high turbidity removal capacity (86.76±1.52%, 10min) and efficient aniline blue (AB) removal capacity (56.46±1.41%, 30min). The mechanism of AB removal by the periphytic EPS seemed to be a combined technique of “adsorption-flocculation”. This study reveals the flocculating capability of periphytic EPS, and suggests that periphytic biofilms are novel sources for bioflocculants preparation.
Using Microbial Aggregates to Entrap Aqueous Phosphorus Xu, Ying; Wu, Yonghong; Esquivel-Elizondo, Sofia ...
Trends in biotechnology (Regular ed.),
November 2020, 2020-11-00, 20201101, Volume:
38, Issue:
11
Journal Article
Peer reviewed
The increasing use and associated loss of phosphorus to the environment pose risks to aquatic ecosystems. Technology for phosphorus removal based on microbial aggregates is a natural, ecologically ...widespread, and sustainable reclamation strategy. Two main processes dominate phosphorus removal by microbial aggregates: extra- and intra-cellular entrapment. Extracellular phosphorus entrapment relies on extracellular polymeric substances, while intracellular entrapment uses a wider variety of phosphorus-entrapping mechanisms. In microbial aggregates, microalgae–bacteria interactions, quorum sensing, and acclimation can enhance phosphorus removal. Based on these insights, we propose novel avenues for entrapping phosphorus using ecological and genetic engineering, manipulated interactions, and integrated processes to create phosphorus removal technology mediated by microbial aggregates.
Phosphorus (P) entrapment by microbial aggregates is a natural process that requires relatively small amounts of operational inputs and is eco-friendly; it offers an effective means to remove P from eutrophic surface waters.Extracellular polymeric substances in microbial aggregates play an important role in extracellular P entrapment due to their inherent characteristics, chemical composition, and role in aggregation.Multiple mechanisms allow intracellular P entrapment by microalgae and polyphosphate-accumulating microorganisms in microbial aggregates.In microbial aggregates, microalgae–bacteria interactions, quorum sensing, and adaption can enhance the community’s ability to remove P.Ecological and genetic engineering, regulation of interactions, and integrated processes (microbial aggregates with enhanced biological P removal and bioelectrochemical system), can help to design P removal technology based on microbial aggregates.
Abstract
Carbon monoxide (CO)-metabolism and phenotypic and phylogenetic characterization of a novel anaerobic, mesophilic and hydrogenogenic carboxydotroph are reported. Strain SVCO-16 was isolated ...from anaerobic sludge and grows autotrophically and mixotrophically with CO. The genes cooS and cooF, coding for a CO dehydrogenase complex, and genes similar to hycE2, encoding a CO-induced hydrogenase, were present in its genome. The isolate produces H2 and CO2 from CO, and acetate and formate from organic substrates. Based on the 16S rRNA sequence, it is an Alphaproteobacterium most closely related to the genus Pleomorphomonas (98.9%–99.2% sequence identity). Comparison with other previously characterized Pleomorphomonas showed that P. diazotrophica and P. oryzae do not metabolize CO, and P. diazotrophica does not grow anaerobically with organic substrates. Average nucleotide identity values between strain SVCO-16 and P. diazotrophica, P. oryzae or P. koreensis were 86.66 ± 0.21%. These values are below the boundary to define species (95%–96%). Digital DNA-DNA hybridization estimates between strain SVCO-16 and reference strains were also below the 70% threshold for species delineation: 29.1%–34.5%. Based on the differences in CO metabolism, genome analyses and cellular fatty acid composition, the isolate should be classified into the genus Pleomorphomonas as a representative of a novel species, Pleomorphomonas carboxyditropha. The type strain of Pleomorphomonas carboxyditropha is SVCO-16T (strain deposit numbers, DSM 106132T and TSD-119T).
The anaerobic metabolism and phenotypic characterization of a novel mesophilic Alphaproteobacterium that produces H2 and CO2 from CO is described and compared to closely related bacteria.
Medium‐chain fatty acids (MCFA) are important biofuel precursors. Carbon monoxide (CO) is a sustainable electron and carbon donor for fatty acid elongation, since it is metabolized to MCFA ...precursors, it is toxic to most methanogens, and it is a waste product generated in the gasification of waste biomass. The main objective of this work was to determine if the inhibition of methanogenesis through the continuous addition of CO would lead to increased acetate or MCFA production during fermentation of ethanol. The effects of CO partial pressures (PCO; 0.08–0.3 atm) on methanogenesis, fatty acids production, and the associated microbial communities were studied in batch cultures fed with CO and ethanol. Methanogenesis was partially inhibited at PCO ≥ 0.11 atm. This inhibition led to increased acetate production during the first phase of fermentation (0–19 days). However, a second addition of ethanol (day 19) triggered MCFA production only at PCO ≥ 0.11 atm, which probably occurred through the elongation of acetate with CO‐derived ethanol and H2:CO2. Accordingly, during the second phase of fermentation (days 20–36), the distribution of electrons to acetate decreased at higher PCO, while electrons channeled to MCFA increased. Most probably, Acetobacterium, Clostridium, Pleomorphomonas, Oscillospira, and Blautia metabolized CO to H2:CO2, ethanol and/or fatty acids, while Peptostreptococcaceae, Lachnospiraceae, and other Clostridiales utilized these metabolites, along with the provided ethanol, for MCFA production. These results are important for biotechnological systems where fatty acids production are preferred over methanogenesis, such as in chain elongation systems and microbial fuel cells.
Continuous addition of carbon monoxide (CO) (140–428 mmol/L) at CO partial pressures ≥0.11 atm to fermentation with small amounts of ethanol (22 mmol/L) inhibited methanogenesis and led to elongation of acetate (produced from ethanol) to propionate, butyrate and medium‐chain fatty acids (MCFA) with CO‐derived H2:CO2 and ethanol. Clostridium, Peptostreptococcaceae, Lachnospiraceae, and other Clostridiales most likely partnered with carboxidotrophs, potentially Acetobacterium, Pleomorphomonas, Oscillospira, and Blautia species, for valerate, caproate, and heptanoate production.
The dielectric properties of
Bi
2
Ti
2
O
7
were explored as a function of temperature and frequency. A comparison between the dielectric response of the well‐known
Bi
1.5
Zn
0.92
Nb
1.5
O
6.92
(
BZN
...) pyrochlore and the recently available
Bi
2
Ti
2
O
7
sintered ceramic revealed considerable differences, which indicate that chemical disorder, and not atomic displacement on its own, is chiefly responsible for the dielectric relaxation in bismuth pyrochlores. A low‐frequency (<10 kHz) and relatively high‐temperature (~125 K) dielectric relaxation was observed in
Bi
2
Ti
2
O
7
. An Arrhenius function was used to model the relaxation behavior and yielded an activation energy of 0.162 eV and an attempt jump frequency of ~1 MHz. This response is consistent with space charge polarization and not the result of dipolar or ionic disorder.
PDF
