Detection of active, potentially acetate-oxidizing syntrophs in an anaerobic digester by flux measurement and formyltetrahydrofolate synthetase (FTHFS) expression profiling

Syntrophic oxidation of acetate, so-called reversed reductive acetogenesis, is one of the most important degradation steps in anaerobic digesters. However, little is known about the genetic diversity of the micro-organisms involved. Here we investigated the activity and composition of potentially acetate-oxidizing syntrophs using a combinatorial approach of flux measurement and transcriptional profiling of the formyltetrahydrofolate synthetase (FTHFS) gene, an ecological biomarker for reductive acetogenesis. During the operation of a thermophilic anaerobic digester, volatile fatty acids were mostly depleted, suggesting a high turnover rate for dissolved H2, and hydrogenotrophic methanogens were the dominant archaeal members. Batch cultivation of the digester microbiota with 13C-labelled acetate indicated that syntrophic oxidation accounted for 13.1–21.3 % of methane production from acetate. FTHFS genes were transcribed in the absence of carbon monoxide, methoxylated compounds and inorganic electron acceptors other than CO2, which is implicated in the activity of reversed reductive acetogenesis; however, expression itself does not distinguish whether biosynthesis or biodegradation is functioning. The mRNA- and DNA-based terminal RFLP and clone library analyses indicated that, out of nine FTHFS phylotypes detected, the FTHFS genes from the novel phylotypes I–IV in addition to the known syntroph Thermacetogenium phaeum (i.e. phylotype V) were specifically expressed. These transcripts arose from phylogenetically presumed homoacetogens. The results of this study demonstrate that hitherto unidentified phylotypes of homoacetogens are responsible for syntrophic acetate oxidation in an anaerobic digester.

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A Simple and Accurate Approach for Determining the VFA Concentration in Anaerobic Digestion Liquors, Relying on Two Titration Points and an External Inorganic Carbon Analysis

ChemEngineering ◽

10.3390/chemengineering5020015 ◽

2021 ◽

Vol 5 (2) ◽

pp. 15

Author(s):

Paz Nativ ◽

Yonatan Gräber ◽

Yaron Aviezer ◽

Ori Lahav

Keyword(s):

Partial Pressure ◽

Volatile Fatty Acids ◽

Inorganic Carbon ◽

Strong Acid ◽

Direct Analysis ◽

Anaerobic Digesters ◽

Acid Titration ◽

Partial Pressure Of Co2 ◽

Ph Range

A new analytic approach is presented for determining the total volatile fatty acids (VFAT) concentration in anaerobic digesters. The approach relies on external determination of the inorganic carbon concentration (CT) in the analyzed solution, along with two strong-acid titration points. The CT concentration can be determined by either a direct analysis (e.g., by using a TOC device) or by estimating it from the recorded partial pressure of CO2(g) in the biogas (often a routine analysis in anaerobic digesters). The titration is carried out to pH 5.25 and then to pH 4.25. The two titration results are plugged into an alkalinity-mass-based equation and then the two terms are subtracted from each other to yield an equation in which VFAT is the sole unknown (since CT is known and the effect of the total orthophosphate and ammonia concentrations is shown to be small at this pH range). The development of the algorithm and its verification on four anaerobic reactor liquors is presented, on both the raw water and on acetic acid-spiked samples. The results show the method to be both accurate (up to 2.5% of the expected value for VFAT/Alkalinity >0.2) and repetitive when the total orthophosphate and ammonia concentrations are known, and fairly accurate (±5% for VFAT >5 mM) when these are completely neglected. PHREEQC-assisted computation of CT from the knowledge of the partial pressure of CO2(g) in the biogas (and pH, EC and temperature in the liquor) resulted in a very good estimation of the CT value (±3%), indicating that this technique is adequate for the purpose of determining VFAT for alarming operators in case of process deterioration and imminent failure.

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Enhanced lipid accumulation in Metschnikowia pulcherrima using volatile fatty acids under non-sterile repeated batch cultivation

International Biodeterioration & Biodegradation ◽

10.1016/j.ibiod.2021.105256 ◽

2021 ◽

Vol 163 ◽

pp. 105256

Author(s):

Qian Li ◽

Danyang Wang ◽

Xiaolei Liu ◽

Anjie Li ◽

Kartik Chandran

Keyword(s):

Fatty Acids ◽

Lipid Accumulation ◽

Volatile Fatty Acids ◽

Batch Cultivation ◽

Metschnikowia Pulcherrima ◽

Repeated Batch

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Abrogating the inhibitory effects of volatile fatty acids and ammonia in overloaded food waste anaerobic digesters via the supplementation of nano-zero valent iron modified biochar

The Science of The Total Environment ◽

10.1016/j.scitotenv.2022.152968 ◽

2022 ◽

pp. 152968

Author(s):

Ee Yang Lim ◽

Jonathan Tian En Lee ◽

Le Zhang ◽

Hailin Tian ◽

Kok Chung Ong ◽

...

Keyword(s):

Fatty Acids ◽

Food Waste ◽

Volatile Fatty Acids ◽

Zero Valent Iron ◽

Inhibitory Effects ◽

Anaerobic Digesters ◽

Modified Biochar ◽

Nano Zero Valent Iron

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Application of Methanobrevibacter acididurans in anaerobic digestion

Water Science & Technology ◽

10.2166/wst.2004.0366 ◽

2004 ◽

Vol 50 (6) ◽

pp. 109-114 ◽

Cited By ~ 9

Author(s):

D.V. Savant ◽

D.R. Ranade

Keyword(s):

Fatty Acids ◽

Anaerobic Digestion ◽

Methane Production ◽

Volatile Fatty Acids ◽

Low Ph ◽

Anaerobic Digesters ◽

Hydrogenotrophic Methanogen ◽

Distillery Wastewater ◽

Acid Tolerant ◽

Acidic Conditions

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.

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Nocardia effects in waste activated sludge

Water Science & Technology ◽

10.2166/wst.1998.0102 ◽

1998 ◽

Vol 38 (2) ◽

pp. 49-54 ◽

Cited By ~ 7

Author(s):

Krishna R. Pagilla ◽

David Jenkins ◽

Wendell Kido

Keyword(s):

Activated Sludge ◽

Foam Stability ◽

Anaerobic Digester ◽

Waste Activated Sludge ◽

Dissolved Air Flotation ◽

Anaerobic Digesters ◽

Primary Sludge ◽

Mixed Liquor ◽

Dissolved Air ◽

Batch Foaming

Two effects of Nocardia in waste activated sludge (WAS) were investigated: (i) the influence of WAS in the solids treatment recycle streams on Nocardia persistence in the activated sludge, and (ii) the effect of Nocardia in WAS on anaerobic digester foaming. About 4% of the Nocardia present in the mixed liquor was due to seeding from the WAS solids in the dissolved air flotation thickener recycle stream recycle. Nocardia filaments in WAS at levels of between 104 to 106 intersections/g VSS resulted in Nocardia levels of approximately 104 to 105 intersections/g VSS in anaerobic digesters that treated both WAS and primary sludge. The effect of disinfecting these Nocardia filaments in the WAS with Cl2 was investigated at Cl2 dose ranges of 20-60 mg Cl2/l WAS and 100-200 mg Cl2/l WAS on a lab scale using batch foaming tests to assess success. Chlorination with 20 - 60 mg Cl2/l WAS approximately doubled both sludge foaming potential and foam stability. At Cl2 doses of 100-200 mg Cl2/l WAS, foaming potential was increased almost 10-fold, and foam stability was increased by 2.5 times. These results indicate that chlorination of WAS feed to an anaerobic digester for inactivation of Nocardia should not be practiced.

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Recovery of volatile fatty acids (VFA) from complex waste effluents using membranes

Water Science & Technology ◽

10.2166/wst.2013.717 ◽

2013 ◽

Vol 69 (3) ◽

pp. 495-503 ◽

Cited By ~ 32

Author(s):

M.-P. Zacharof ◽

R. W. Lovitt

Keyword(s):

Fatty Acids ◽

Acetic Acid ◽

Butyric Acid ◽

Volatile Fatty Acids ◽

Agricultural Waste ◽

Permeate Flux ◽

Anaerobic Digesters ◽

Waste Effluents

Waste effluents from anaerobic digesters of agricultural waste were treated with a range of membranes, including microfiltration and nanofiltration (NF), to concentrate volatile fatty acids (VFA). Microfiltration was applied successfully to produce sterile, particle-free solutions with a VFA concentration of 21.08 mM of acetic acid and 15.81 mM of butyric acid. These were further treated using a variety of NF membranes: NF270 (Dow Chemicals, USA), HL, DL, DK (Osmonics, USA) and LF10 (Nitto Denko, Japan), achieving retention ratios of up to 75%, and giving retentates of up to 53.94 mM of acetate and 28.38 mM of butyrate. DK and NF270 membranes were identified as the best candidates for VFA separation and concentration from these multicomponent effluents, both in terms of retention and permeate flux. When the effluents are adjusted to alkali conditions, the highest productivity, retention and flux were achieved at pH 7. At higher pH there was a significant reduction in flux.

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Plantwide modelling – anaerobic digestion of waste sludge from parent nutrient (N and P) removal systems

Water SA ◽

10.17159/wsa/2019.v45.i3.6698 ◽

2019 ◽

Vol 45 (3 July) ◽

Author(s):

DS Ikumi ◽

GA Ekama

Keyword(s):

Anaerobic Digestion ◽

Activated Sludge ◽

Volatile Fatty Acids ◽

Treatment Plant ◽

Anaerobic Digester ◽

Hydrolysis Rate ◽

Biological Nutrient Removal ◽

Biomass Hydrolysis ◽

Behavioural Patterns ◽

Anaerobic Zone

Wastewater treatment plant (WWTP) mathematical models are based on the behavioural patterns of microorganisms involved in the treatment process. These microorganisms are assumed incapable of thinking or planning but simply act according to the capabilities afforded to them by their surrounding conditions – hence different microorganisms pre-dominate different WWTP zones according to how well the conditions suit them. When waste activated sludge (WAS) from biological nutrient removal (BNR) activated sludge (AS) systems, containing phosphorus-accumulating organisms (PAOs), is fed to an anaerobic digester, there is a release of high quantities of metals, phosphorus (P) and nitrogen (N). The manner in which we model the release of these metals and nutrients significantly affects the accuracy of predicted anaerobic digestion (AD) outcomes. Previous studies of PAOs show that in the anaerobic zone of the AS system, they can form energy-rich poly3-hydroxybutyrate (PHB) at the expense of their aerobically generated polyphosphate (PP). Thus, it is expected that the PAOs containing PP sent into an anaerobic digester with volatile fatty acids (VFAs) present, would utilize their PP reserves as they would in the anaerobic zone of an AS process ending up with formation and storage of some PHB. Ultimately, all the stored products of the PAO get released, since there is no alternating aerobic environment to cater for their growth. Since it has been established that the PP release in the AD occurs much faster than the PAO biomass hydrolysis rate, it is modelled as a separate process. Steps are presented in the development of this PP release mass-balanced stoichiometries that occur with AD of PAOs. By comparing outcomes from these proposed stoichiometries against measured experimental data, it is noticed that better predictions are obtained with acetate uptake for PHB formation than when modelling the AD PP release to occur with PAO death and hydrolysis.

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Magnetite nanoparticles enhance the bioelectrochemical treatment of municipal sewage by facilitating the syntrophic oxidation of volatile fatty acids

Journal of Chemical Technology & Biotechnology ◽

10.1002/jctb.6120 ◽

2019 ◽

Vol 94 (10) ◽

pp. 3134-3146 ◽

Cited By ~ 4

Author(s):

Carolina Cruz Viggi ◽

Stefania Casale ◽

Habib Chouchane ◽

Refka Askri ◽

Stefano Fazi ◽

...

Keyword(s):

Fatty Acids ◽

Magnetite Nanoparticles ◽

Volatile Fatty Acids ◽

Municipal Sewage ◽

Syntrophic Oxidation

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Studies of the Production of Volatile Fatty Acids in the Anaerobic Digestion of Municipal Sludge

Water Quality Research Journal ◽

10.2166/wqrj.1986.006 ◽

1986 ◽

Vol 21 (1) ◽

pp. 58-70 ◽

Cited By ~ 1

Author(s):

P.H. Jones ◽

J. Szekely

Keyword(s):

Fatty Acids ◽

Anaerobic Digestion ◽

Volatile Fatty Acids ◽

Gas Production ◽

Municipal Sludge ◽

Anaerobic Digesters ◽

Effect Of Ph ◽

Commercial Value

Abstract Volatile fatty acids (VFA’s) produced during anaerobic digestion of sludge have higher commercial value than methane produced subsequently. Therefore it was decided to determine conditions necessary to maximise production of VFA’s. Five anaerobic digesters were operated in parallel in the laboratory to investigate the effect of pH on the formation of VFA’s. Concentrations of individual fatty acids were measured. Both VFA production as well as gas production was favoured by pH approaching neutrality.

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