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Cited by 163Anaerobic Digestion and Biogas ProductionEnvironmental Chemistry and AnalysisMicrobial Fuel Cells and Bioremediation

The DOI matches its Crossref record; 17 of the 17 references it cites were found in a registry or an index; none of the 17 sources its claims cite is checked for support yet.

Effects of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part II: Oleic acid toxicity and biodegradability

Open access
Alves, M.M, Mota Vieira, J.A, Álvares Pereira, R.M, Pereira, M.A, Mota, M·2001·Water Research
DOI 10.1016/s0043-1354(00)00242-6
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Abstract

Oleic acid toxicity and biodegradability were followed during long-term operation of two similar anaerobic fixed-bed units. When treating an oleate based effluent, the sludge from the bioreactor that was acclimated with lipids during the first operation period, showed a higher tolerance to oleic acid toxicity (IC50 = 137 mg/l) compared with the sludge fed with a non-fat substrate (IC50 = 80 mg/l). This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methane production rates between 33 and 46 mlCH4(STP)/gVS.day and maximum percentages of methanization between 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l. When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter, possibly oleate or an intermediate of its degradation, e.g. stearate that was degraded at a maximum rate of 99 mlCH4(STP)/gVS.day. This suggests the possibility of using adsorption-degradation cycles for the treatment of LCFA based effluents. Both tolerance to toxicity and biodegradability of oleic acid were improved by acclimatization with lipids or oleate below a threshold concentration.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Long-term operation of two anaerobic fixed-bed units showed that sludge pre-exposed to lipids developed greater tolerance to oleic acid toxicity and higher oleate biodegradation capacity than sludge fed a non-fat substrate. When oleate became the sole carbon source, biomass became encapsulated with adsorbed organic matter, suggesting possible adsorption–degradation cycles for lipid-rich effluents.

Key findings

  • Sludge acclimated with lipids had higher tolerance to oleic acid toxicity (IC50 = 137 mg/l) than sludge fed a non-fat substrate (IC50 = 80 mg/l); across the work, IC50 values ranged from 30 to 295 mg/l.
  • The lipid-acclimated sludge achieved maximum methane production rates between 33 and 46 mlCH4(STP)/gVS.day and maximum methanization percentages between 85 and 98% for oleate concentrations of 500–900 mg/l.
  • When oleate was the sole carbon source, biomass became encapsulated with organic matter, possibly oleate or an intermediate such as stearate, which was degraded at a maximum rate of 99 mlCH4(STP)/gVS.day.
  • Blank-vial background methane production from adsorbed matter reached 99 and 84 mlCH4(STP)/gVS.day for reactors RI and RII, respectively—two-fold higher than the maximum oleate degradation rate measured in biodegradability tests.

Methods

  • Two similar anaerobic fixed-bed units were operated long-term: start-up on skim milk; Period I had RI shifted to whole milk while RII continued skim milk for 246 days; Period II fed increasing oleate with skim milk as co-substrate; Period III fed oleate as the sole carbon source.
  • Toxicity and biodegradability batch tests used a pressure transducer technique under strict anaerobic conditions, with basal medium at pH 7.0–7.2 and no added calcium or trace nutrients.
  • Toxicity tests added 30 mM acetate plus oleate at 100, 300, 500, 700, and 900 mg/l in triplicate; biodegradability tests added the same oleate concentrations in duplicate and measured maximum methane production rate, percentage of methanization, and lag phases, with specific values divided by vial VS content.

Limitations

  • The paper states that the hypothesis that oleate was reduced to stearate prior to adsorption needs experimental validation.
  • Evident from the text: toxicity and biodegradability were assessed in batch assays with suspended sludge at 37°C without added calcium or magnesium, so results may not directly translate to continuous high-rate digesters and are sensitive to temperature, cations, and sludge characteristics.
  • Evident from the text: at the end of operation, extremely high background methane production from adsorbed organic matter complicated interpretation, although background methane was discounted in reported MMPR and PM values.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/s0043-1354(00)00242-6

Cites

17 of 17 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 17 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The methane production rate from adsorbed matter was two-fold higher than the maximum oleate degradation rate measured in the biodegradability tests.

    “The methane production rate from this adsorbed matter (99 and 84 mlCH 4(STP) /gVS.day, for RI and RII, respectively) was two-fold higher than the maximum oleate degradation rate measured in the biodegradability tests.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The adsorbed organic matter responsible for background methane production is oleate or an intermediate of its degradation.
  • Findingown data

    Sludge from the bioreactor acclimated with lipids during the first operation period showed higher tolerance to oleic acid toxicity (IC50 = 137 mg/l) than sludge fed a non-fat substrate (IC50 = 80 mg/l).

    “the sludge from the bioreactor that was acclimated with lipids during the ®rst operation period, showed a higher tolerance to oleic acid toxicity (IC 50 =137 mg/l) compared with the sludge fed with a non-fat substrate (IC 50 =80 mg/l).”
    • Also stated in: § CONCLUSIONS · plain
      “When treating an oleate based euent, the sludge that had been pre-exposed to lipids showed higher tolerance to oleic acid toxicity than the sludge that had been fed with a non-fat substrate.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The two anaerobic fixed-bed units (RI and RII) were similar enough that differences in sludge behavior can be attributed to substrate composition (lipids vs non-fat).
  • Findingown data

    When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter.

    “When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter, possibly oleate or an intermediate of its degradation, e.g.stearate that was degraded at a maximum rate of 99 mlCH 4(STP) /gVS.day.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The adsorbed organic matter responsible for background methane production is oleate or an intermediate of its degradation.
  • Findingown data

    Acetoclastic bacteria are more susceptible to oleic acid than hydrogenophilic bacteria.

    “which con®rms the higher susceptibility of acetoclastic bacteria to oleic acid, relative to hydrogenophilic bacteria, as reported by Hanaki et al. (1981).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hanaki et al., 1981 source
  • Findingnone given

    The highest background methane production rate was obtained for the highest concentration of background substrate.

    “It was also observed that the highest background methane production rate was obtained for the highest concentration of background substrate.”
    Quote in the paperNot a substantial claim
  • It may state two separate claims as one. 22
  • Probably not a substantial claim. 12

  • It may state two separate claims as one.

    Findingown data

    The methane production rate from adsorbed matter was 99 mlCH4(STP)/gVS.day for RI and 84 mlCH4(STP)/gVS.day for RII.

    “The methane production rate from this adsorbed matter (99 and 84 mlCH 4(STP) /gVS.day, for RI and RII, respectively) was two-fold higher than the maximum oleate degradation rate measured in the biodegradability tests.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The adsorbed organic matter responsible for background methane production is oleate or an intermediate of its degradation.

  • It may state two separate claims as one.

    Findingown data

    The sludge acclimatized with lipids showed increasing biodegradation capacity of oleic acid along the trial period, with maximum methane production rates between 33 and 46 mlCH4(STP)/gVS.day and maximum percentages of methanization between 85 and 98% for oleate concentrations between 500 and 900 mg/l.

    “This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methane production rates between 33 and 46 mlCH 4(STP) /gVS.day and maximum percentages of methanization between 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l.”
    • Also stated in: § CONCLUSIONS · plain
      “The sludge that had been acclimatized with lipids showed an increasing biodegradation capacity of oleic acid along the trial period.Maximum methane production rates between 33 and 46 mlCH 4(STP) /gVS.day and maximum percentages of methanization between 85 and 98% were obtained for the range of concentrations between 500 and 900 mg/l.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    When feeding changed to a blend of skim milk and sodium oleate (Period II), sludge RII lost its resistance whereas sludge from RI achieved a maximum of tolerance to oleate during this period.

    “However, when the feeding was changed to a blend of skim milk and sodium oleate (Period II) the sludge RII lost its resistance whereas sludge from RI achieved a maximum of tolerance to oleate during this period.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The sludge from RI exhibited the highest capacity of oleate biodegradation, evidenced by the highest methane production rates, the highest percentages of methanization and the lowest lag phases.

    “This sludge exhibited the highest capacity of oleate biodegradation evidenced by the highest methane production rates, the highest percentages of methanization and the lowest lag phases.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Although no effect was evident in the specific acetoclastic activity, which was enhanced for both sludges during Period I, the precontact with lipids delayed acetate degradation when in the presence of sodium oleate.

    “Although no eect was evident in the speci®c acetoclastic activity which was enhanced for both sludges during this period (see Part I), it was clear that the precontact with lipids delayed the acetate degradation, when in the presence of sodium oleate.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    During Period II, when oleate was fed with a co-substrate, no significant background methane production was detected, and it was reduced compared with values of Period I.

    “During Period II, when oleate was fed with a co-substrate, no signi®cant background methane production was detected, and was reduced by comparison with the values of Period I (Table 3).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingnone given

    This behaviour was typical during Period I, but the differences between the two sludges became more pronounced towards the end of this operation period.

    “This behaviour was typical during Period I, but the dierences between the two sludges became more pronounced towards the end of this operation period.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The sludge collected at the end of the experiment, when oleate was the sole carbon source, exhibited percentages of methanization higher than 80% for concentrations of 700 and 900 mg/l, but methane production rates decreased significantly and lag phases increased.

    “The sludge collected at the end of the experiment, when oleate was the sole carbon source fed to the reactor, exhibited percentages of methanization higher than 80% for the concentrations of 700 and 900 mg/l, but methane production rates decreased signi®cantly and lag phases increased.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The potential specific acetoclastic activity followed the same decreasing trend observed during Period II, and resistance to sodium oleate decreased for both sludges.

    “The potential speci®c acetoclastic activity followed the same decreasing trend observed during Period II (see Part I), and the resistance to sodium oleate decreased for both sludges.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    During Period I, tolerance to oleate increased for both sludges, but particularly for sludge RII.

    “During Period I, the tolerance to oleate increased for both sludges, but particularly for sludge RII.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    There was an increase in methane production rate and percentage of methanization for all concentrations of oleate until Period II, when oleate was fed with a co-substrate.

    “In general, it was shown that there was an increase in the methane production rate and in the percentage of methanization for all concentrations of oleate until Period II, when oleate was fed with a co-substrate.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Acetate and oleate degradation by sludge from RII followed a diauxic behavior and no lag phase was observed over the range of concentrations under study.

    “However, acetate and oleate degradation by sludge from RII followed a diauxic behavior and no lag phase was observed over the range of concentrations under study.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    In the inoculum, the IC50 of sodium oleate was 50 mg/l for acetoclastic bacteria and 200 mg/l for hydrogenophilic bacteria.

    “The values obtained for IC 50 were 50 mg/l for acetoclastic bacteria and 200 mg/l for the hydrogenophilic bacteria, which con®rms the higher susceptibility of acetoclastic bacteria to oleic acid, relative to hydrogenophilic bacteria, as reported by Hanaki et al. (1981).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationown data

    Long term contact with lipids, or oleate below a threshold concentration, induced adaptation to biodegradation of oleic acid.

    “The long term contact with lipids, or oleate below a threshold concentration, induced adaptation to biodegradation of oleic acid.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The threshold concentration of oleate below which adaptation occurs is a real and relevant phenomenon.

  • It may state two separate claims as one.

    Interpretationreasoning

    The addition of oleate above a threshold concentration affected the acetoclastic activity and the tolerance of these bacteria to oleate.

    “Therefore, the addition of oleate above a threshold concentration aected the acetoclastic activity as well as the tolerance of these bacteria to oleate.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may state two separate claims as one.

    Premisecitation

    Most previous works report on results from batch assays and the general conclusion is that no adaptation of methanogenic bacteria to LCFA occurs.

    “Adaptation of methanogenic bacteria to LCFA is discussed in the literature, but most of the previous works report on results from batch assays (Hanaki et al., 1981;Koster and Cramer, 1987;Angelidaki and Ahring, 1992) and the general conclusion is that no adaptation of methanogenic bacteria to LCFA occurs.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Hanaki et al., 1981 source
    • cites Koster and Cramer, 1987 source
    • cites Angelidaki and Ahring, 1992 source

  • It may state two separate claims as one.

    Premisecitation

    The first step in oleate degradation is the reduction of oleate to stearate, which is a saturated LCFA, less toxic than oleic acid.

    “According to the degradation pathways of oleic acid described by Weng and Jeris (1976), the ®rst step in oleate degradation is the reduction of oleate to stearate, which is a saturated LCFA, less toxic than oleic acid.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Weng and Jeris, 1976 source

  • It may state two separate claims as one.

    Interpretationown data

    The degradation of adsorbed organic matter was delayed by added oleic acid, suggesting that this LCFA exerted a toxic effect on the degradation of the adsorbed matter.

    “This indicates that the degradation of the adsorbed organic matter was delayed by the added oleic acid, suggesting that this LCFA exerted a toxic eect on the degradation of the adsorbed matter.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The adsorbed organic matter responsible for background methane production is oleate or an intermediate of its degradation.

  • It may state two separate claims as one.

    Interpretationown data

    The pre-contact with lipids affected the type of tolerance developed by the sludge, and pre-exposition to lipids seemed beneficial to the development of resistance to oleic acid in the treatment of an effluent containing this LCFA.

    “In other words, it seems that the pre-contact with lipids aected the type of tolerance developed by the sludge, the pre-exposition to lipids seeming to be bene®cial to the development of resistance to oleic acid in the treatment of an euent containing this LCFA.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The two anaerobic fixed-bed units (RI and RII) were similar enough that differences in sludge behavior can be attributed to substrate composition (lipids vs non-fat).

  • Probably not a substantial claim.

    Study design and conductnone given

    The specific values of degradation rate and percentage of methanization were obtained by dividing the methane production rates by the VS content of each vial determined at the end of the experiment.

    “The speci®c values of degradation rate and percentage of methanization were obtained by dividing the methane production rates by the VS content of each vial determined at the end of the experiment.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may state two separate claims as one.

    Premisecitation

    The existing literature suggests that LCFA exert a bactericidal effect on methanogenic bacteria and no adaptation was observed.

    “The existing literature suggests that LCFA exert a bactericidal eect on methanogenic bacteria and no adaptation was observed.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Rinzema et al., 1994 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductcitation

    The fixed-bed reactors were specially designed to allow the biomass to be periodically withdrawn.

    “The ®xed-bed reactors were specially designed to allow the biomass to be periodically withdrawn (Alves et al., 1998).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Alves et al., 1998 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Hanaki et al. (1981) concluded that oleate adsorbed to the biomass within 24 h.

    “Hanaki et al. (1981) concluded that oleate adsorbed to be biomass within 24 h.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hanaki et al., 1981 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Toxicity batch experiments were performed in triplicate assays.

    “Toxicity batch experiments were performed in triplicate assays.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisenone given

    In none of the previous works was it proven that the adsorbed product was effectively oleic acid.

    “However, in none of these works was it proven that the adsorbed product was eectively oleic acid.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductnone given

    Strict anaerobic conditions were maintained.

    “Strict anaerobic conditions were maintained.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Study design and conductcitation

    Methanogenic toxicity and biodegradability tests were performed using a pressure transducer technique.

    “Methanogenic toxicity and biodegradability tests were performed using a pressure transducer technique (Colleran et al., 1992;Colleran and Pistilli, 1994).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Colleran et al., 1992 source
    • cites Colleran and Pistilli, 1994

  • Probably not a substantial claim.

    Study design and conductnone given

    Background methane production due to residual substrate was discounted in the values of MMPR and PM.

    “Background methane production due to residual substrate was discounted in the values of MMPR and PM.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    Sodium oleate was used as a model for LCFA because it is generally the most abundant LCFA in wastewater, has good solubility, is the most important LCFA produced by whole milk degradation, and is one of the more toxic LCFA.

    “Sodium oleate was used as a model for LCFA because it is, in general, the most abundant of all LCFA present in wastewater (Komatsu et al., 1991), has a good solubility, it is the most important LCFA produced by whole milk degradation (Hanaki et al., 1981) and is one of the more toxic LCFA (Galbraith et al., 1971).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Komatsu et al., 1991 source
    • cites Hanaki et al., 1981 source
    • cites Galbraith et al., 1971 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Biodegradability tests were performed in duplicate assays.

    “Biodegradability tests were performed in duplicate assays.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. It may state two separate claims as one.

    Premisecitation

    Oleate adsorption is highly concentration-dependent in batch experiments and induces inhibition of methanogenic bacteria by increasing lag phases before initial methane production.

    “Oleate adsorption was found to be highly concentration-dependent in batch experiments and induced the inhibition of methanogenic bacteria by increasing the lag-phases before initial methane production, whereas in UASB reactors sludge ¯otation was related to LCFA/sludge loading rates.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hwu et al., 1998 source
31 of 31

  • The authors state this as an assumption.

    The adsorbed organic matter responsible for background methane production is oleate or an intermediate of its degradation.

    “possibly oleate or an intermediate of its degradation, e.g.stearate that was degraded at a maximum rate of 99 mlCH 4(STP) /gVS.day.”
    “The high values of background methane production obtained for both sludges at the end of the operation indicate that adsorbed organic mat-ter, possibly oleate or an intermediate of its degradation is still available for degradation.”

  • The paper relies on this without support.

    The two anaerobic fixed-bed units (RI and RII) were similar enough that differences in sludge behavior can be attributed to substrate composition (lipids vs non-fat).

    “Oleic acid toxicity and biodegradability were followed during long-term operation of two similar anaerobic ®xed-bed units.”

  • The paper relies on this without support.

    The batch toxicity and biodegradability assays reflect the behavior of the sludge in the continuous fixed-bed reactors.

    “Methanogenic toxicity and biodegradability tests were performed using a pressure transducer technique (Colleran et al., 1992;Colleran and Pistilli, 1994).”

  • The paper relies on this without support.

    The threshold concentration of oleate below which adaptation occurs is a real and relevant phenomenon.

    “Both tolerance to toxicity and biodegradability of oleic acid were improved by acclimatization with lipids or oleate below a threshold concentration.”

  • The paper relies on this without support.

    The sludge samples taken from the reactors are representative of the reactor biomass at the time of sampling.

    “The ®xed-bed reactors were specially designed to allow the biomass to be periodically withdrawn (Alves et al., 1998).”
5 of 5

Citations

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Hanaki, 1983, Inhibitory and stimulative effects of oleate on methanogenesis from acetate in anaerobic digestion, Technological Report Tohoku University, 48, 123

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Metadata

Authors
Alves, M. M., Mota Vieira, J. A., Álvares Pereira, R. M., Pereira, M. A., & Mota, M.
Affiliations
Universidade do Minho Centro de Engenharia Biológica (PT)
Corresponding author
Mota, M
ORCID
Venue
Water Research
Publisher
Elsevier BV
Published
2001-01
Volume
35
Issue
1
Pages
264-270
ISSN
0043-1354 (ISSN-L)
DOI
10.1016/s0043-1354(00)00242-6
OpenAlex
W2151644418
Cited by
163
References
17
Citations by year
2026: 4 · 2025: 2 · 2024: 1 · 2023: 3 · 2022: 5 · 2021: 7 · 2020: 8 · 2019: 6 · 2018: 7 · 2017: 7 · 2016: 13 · 2015: 7 · 2014: 8 · 2013: 8 · 2012: 12
FWCI
4.79
Type
journal article
Language
en
Open access
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Water Research (publishedVersion)
  • PubMed (publishedVersion)
  • RepositóriUM (Universidade do Minho) (submittedVersion, other-oa)
  • Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) (submittedVersion, cc-by-nc-nd)
Topics
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › Anaerobic Digestion and Biogas Production
  • Physical Sciences › Environmental Science › Environmental Chemistry › Environmental Chemistry and Analysis
  • Physical Sciences › Environmental Science › Environmental Engineering › Microbial Fuel Cells and Bioremediation
Keywords
oleic acid, lipotoxicity, anaerobic fixed-bed reactor, biodegradability, sludge acclimatization, long-chain fatty acids, methane production, anaerobic digestion
MeSH terms
Biodegradation, Environmental, Kinetics, Methane, Sewage, Stearic Acids, Biomass, Bioreactors, Oleic Acid, Euryarchaeota

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