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Rheology and Oil–Water Emulsion Stability During Biodegradation of Hydrolyzed Polyacrylamide by Delftia lacustris EPDB-8.

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Title: Rheology and Oil–Water Emulsion Stability During Biodegradation of Hydrolyzed Polyacrylamide by Delftia lacustris EPDB-8.
Authors: Sun, Bingjian1,2 (AUTHOR), Li, Yanshuo1,2 (AUTHOR), Liu, Wei3 (AUTHOR), Hu, Xin1,2 (AUTHOR), Guo, Shichong1,2 (AUTHOR), Li, Yiming1,2,3 (AUTHOR), Lu, Jinren2 (AUTHOR), Li, Haoshuai1,2 (AUTHOR), Bao, Mutai1,2 (AUTHOR) mtbao@ouc.edu.cn
Source: Polymers (20734360). Jun2026, Vol. 18 Issue 11, p1268. 18p.
Subjects: Biodegradation, Demulsification, Rheology, Emulsions, Enhanced oil recovery, Bacteria, Oil field brines, Polyacrylamide
Abstract: Hydrolyzed polyacrylamide stabilized oil-in-water emulsions are highly persistent because the polymer strengthens both continuous-phase rheology and the oil–water interfacial film, making demulsification difficult in polymer-flooding produced liquids. Here, an hydrolyzed polyacrylamide degrading bacterium, Delftia lacustris EPDB-8, was isolated, and its ability to destabilize hydrolyzed polyacrylamide-containing emulsions was investigated from molecular, bulk rheological, and interfacial perspectives. EPDB-8 effectively degraded HPAM, causing marked reductions in total organic carbon, total nitrogen, absolute zeta potential, and polymer molecular weight, with an approximately 63-fold decrease after 7 days. SEM, FT-IR, and GPC analyses showed that biodegradation proceeded through deamidation and random chain scission, collapsing the polymer network and generating low-molecular-weight fragments. Driven by bacterial hydrolyzed polyacrylamide degradation, these structural alterations disrupted the viscoelastic composite interfacial film formed by hydrolyzed polyacrylamide and indigenous surface-active species, directly causing emulsion stabilization to shift from polymer-assisted viscous and steric protection to a less effective asphaltene-dominated interfacial structure and thereby accelerating droplet aggregation, coalescence, and phase separation. Although bacterial cells exerted a transient particle-assisted interfacial effect, long-term emulsion stability remained governed by polymer integrity. This study establishes a mechanistic link between hydrolyzed polyacrylamide biodegradation and the rheological and interfacial evolution governing emulsion breakdown, providing a cost-effective and environmentally benign biological strategy for demulsification and treatment of polymer-flooding produced water. These findings offer practical guidance for the design of microbial-based produced-water treatment systems and contribute to the sustainable management of oilfield wastewater generated during enhanced oil recovery operations. [ABSTRACT FROM AUTHOR]
Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Label: Title
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  Data: Rheology and Oil–Water Emulsion Stability During Biodegradation of Hydrolyzed Polyacrylamide by Delftia lacustris EPDB-8.
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  Data: <searchLink fieldCode="AR" term="%22Sun%2C+Bingjian%22">Sun, Bingjian</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Li%2C+Yanshuo%22">Li, Yanshuo</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Liu%2C+Wei%22">Liu, Wei</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hu%2C+Xin%22">Hu, Xin</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Guo%2C+Shichong%22">Guo, Shichong</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Li%2C+Yiming%22">Li, Yiming</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lu%2C+Jinren%22">Lu, Jinren</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Li%2C+Haoshuai%22">Li, Haoshuai</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bao%2C+Mutai%22">Bao, Mutai</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<i> mtbao@ouc.edu.cn</i>
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  Data: <searchLink fieldCode="JN" term="%22Polymers+%2820734360%29%22">Polymers (20734360)</searchLink>. Jun2026, Vol. 18 Issue 11, p1268. 18p.
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  Data: <searchLink fieldCode="DE" term="%22Biodegradation%22">Biodegradation</searchLink><br /><searchLink fieldCode="DE" term="%22Demulsification%22">Demulsification</searchLink><br /><searchLink fieldCode="DE" term="%22Rheology%22">Rheology</searchLink><br /><searchLink fieldCode="DE" term="%22Emulsions%22">Emulsions</searchLink><br /><searchLink fieldCode="DE" term="%22Enhanced+oil+recovery%22">Enhanced oil recovery</searchLink><br /><searchLink fieldCode="DE" term="%22Bacteria%22">Bacteria</searchLink><br /><searchLink fieldCode="DE" term="%22Oil+field+brines%22">Oil field brines</searchLink><br /><searchLink fieldCode="DE" term="%22Polyacrylamide%22">Polyacrylamide</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Hydrolyzed polyacrylamide stabilized oil-in-water emulsions are highly persistent because the polymer strengthens both continuous-phase rheology and the oil–water interfacial film, making demulsification difficult in polymer-flooding produced liquids. Here, an hydrolyzed polyacrylamide degrading bacterium, Delftia lacustris EPDB-8, was isolated, and its ability to destabilize hydrolyzed polyacrylamide-containing emulsions was investigated from molecular, bulk rheological, and interfacial perspectives. EPDB-8 effectively degraded HPAM, causing marked reductions in total organic carbon, total nitrogen, absolute zeta potential, and polymer molecular weight, with an approximately 63-fold decrease after 7 days. SEM, FT-IR, and GPC analyses showed that biodegradation proceeded through deamidation and random chain scission, collapsing the polymer network and generating low-molecular-weight fragments. Driven by bacterial hydrolyzed polyacrylamide degradation, these structural alterations disrupted the viscoelastic composite interfacial film formed by hydrolyzed polyacrylamide and indigenous surface-active species, directly causing emulsion stabilization to shift from polymer-assisted viscous and steric protection to a less effective asphaltene-dominated interfacial structure and thereby accelerating droplet aggregation, coalescence, and phase separation. Although bacterial cells exerted a transient particle-assisted interfacial effect, long-term emulsion stability remained governed by polymer integrity. This study establishes a mechanistic link between hydrolyzed polyacrylamide biodegradation and the rheological and interfacial evolution governing emulsion breakdown, providing a cost-effective and environmentally benign biological strategy for demulsification and treatment of polymer-flooding produced water. These findings offer practical guidance for the design of microbial-based produced-water treatment systems and contribute to the sustainable management of oilfield wastewater generated during enhanced oil recovery operations. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.3390/polym18111268
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 18
        StartPage: 1268
    Subjects:
      – SubjectFull: Biodegradation
        Type: general
      – SubjectFull: Demulsification
        Type: general
      – SubjectFull: Rheology
        Type: general
      – SubjectFull: Emulsions
        Type: general
      – SubjectFull: Enhanced oil recovery
        Type: general
      – SubjectFull: Bacteria
        Type: general
      – SubjectFull: Oil field brines
        Type: general
      – SubjectFull: Polyacrylamide
        Type: general
    Titles:
      – TitleFull: Rheology and Oil–Water Emulsion Stability During Biodegradation of Hydrolyzed Polyacrylamide by Delftia lacustris EPDB-8.
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              M: 06
              Text: Jun2026
              Type: published
              Y: 2026
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