Bioremediation of perfluorooctanoic acid using microalgae with a transcriptomic approach (vol 488, 137508, 2025)

초록

The authors regret that some errors and overinterpretations were introduced in the originally published article. The primary experimental data, including the overall PFOA removal trends and qualitatively identified by-products, remained unchanged. However, to ensure strict scientific accuracy, the quantitative biodegradation yield of 0.58% (22.7 μg/L) was removed from the manuscript text, as the limitations of the analytical method and arithmetic residual calculation did not sufficiently support this quantitative biodegradation result. While these corrections did not alter the key findings regarding microalgal tolerance and PFOA removal performance, they enhanced analytical rigor and refined the interpretation of the research results. The corrigendum clearly presents the modifications by comparing the original (incorrect) text with the revised (corrected) text for each section, including the highlights, graphical abstract, abstract, introduction, materials and methods, results and discussion, conclusion, and environmental implication. The authors would like to apologize for any inconvenience caused.1)Highlights (table presented) 2)Graphical abstract (table presented) 3) (table presented) 4)Introduction (table presented) 5)2.4. Mass balance evaluation for PFOA removal (table presented) 6)2.6. Analytical methods (table presented) 7)3.3. PFOA removal mechanism and proposed biodegradation pathway (table presented) 8)3.4. Transcriptomic analysis of S. quadricauda exposed to PFOA (table presented) 9)ConclusionsHighlights (table presented) PFOA was biodegraded (22.7 μg/L) via biological removal mechanism of algae.Upregulated oxidoreductase activity plays a significant role in PFOA biodegradation.PFOA was biotransformed via biological removal mechanism of algae.Upregulated oxidoreductase activity plays a significant role in PFOA biotransformation.Graphical abstract (table presented) (table presented) Introduction (table presented) A deeper understanding of the mechanisms included, such as biosorption, bioaccumulation, and biodegradation, will be crucial for advancing the use of microalgae in the bioremediation of PFOA.However, the genes significantly involved in the microalgae-mediated biological degradation of PFOA, as well as the metabolites generated during its degradation and the biodegradation pathway, have yet to be reported.To gain deeper insight into the underlying biological pathways facilitating PFOA biodegradation, transcriptomic analysis was conducted to identify major functional genes that were upregulated in the presence of PFOA.A deeper understanding of the mechanisms included, such as biosorption, bioaccumulation, and biotransformation, will be crucial for advancing the use of microalgae in the bioremediation of PFOA.However, the genes significantly involved in the microalgae-mediated biological degradation of PFOA, as well as the metabolites generated during its degradation and the biotransformation pathway, have yet to be reported.To gain deeper insight into the underlying biological pathways facilitating PFOA biotransformation, transcriptomic analysis was conducted to identify major functional genes that were upregulated in the presence of PFOA.2.4. Mass balance evaluation for PFOA removal (table presented) The mass balance for PFOA removal was determined by quantifying the contributions of abiotic process, biosorption, bioaccumulation, and biodegradation.The biodegraded PFOA (Pt) was calculated using Eq. 2: Pt (%) =(Pa−Pb−Pc−Pd−PePa)× 100 (2)Additionally, degradation products of biodegraded PFOA were assessed using liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) (LC-QTOF, 6545XT advancedbio, Agilent technologies, USA).The mass balance for PFOA removal was determined by quantifying the contributions of abiotic process, biosorption, bioaccumulation.The amounts of biosorbed and bioaccumulated PFOA recovered were quantitatively determined using high-performance liquid chromatography (HPLC).Additionally, degradation products of biotransformed PFOA were assessed using liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) (LC-QTOF, 6545XT advancedbio, Agilent technologies, USA).2.6. Analytical methods (table presented) Degradation products of biodegraded PFOA were examined using a LC-MS/MS equipped with a Zorbax RRHD Eclipse Plus C18 column (2.1 ×50 mm, 1.8 μm, Agilent Technologies, USA) and an InfinityLab PFC delay column at a column temperature of 50℃ and a flow rate of 0.4 mL/min.Identification of PFOA by-products was analyzed qualitatively based on Agilent LC-MS/MS library and US EPA Method 537 [33].PFOA and its biotransformed by-products were examined using a LC-MS/MS equipped with a Zorbax RRHD Eclipse Plus C18 column (2.1 ×50 mm, 1.8 μm, Agilent Technologies, USA) and an InfinityLab PFC delay column at a column temperature of 50℃ and a flow rate of 0.4 mL/min.By-product screening of biotransformed PFOA was performed using high-resolution, accurate-mass LC/Q-TOF-MS, with candidate assignment based on accurate-mass matching and spectral library/database comparison (Agilent Personal Compound Database and Library; National Institute of Standards and Technology). This analytical approach was restricted to qualitative, tentative identification at the candidate level rather than absolute quantification. The limit of detection for PFOA under these conditions was 0.01 μg/L, established at a signal-to-noise ratio of 3.3.3. PFOA removal mechanism and proposed biodegradation pathway (table presented) 3.3. PFOA removal mechanism and proposed biodegradation pathwayTo elucidate the removal mechanism of PFOA, the contents of biosorbed, bioaccumulated, and biodegraded PFOA by S. quadricauda were quantified. S. quadricauda achieved a removal efficiency of 58.2% at 5 ppm of PFOA (Fig. 4), with approximately 12.8% of PFOA biosorbed and 44.8% bioaccumulated (Fig. 6 A). LC-MS/MS analysis confirmed that a fraction of the bioaccumulated PFOA (0.58%, 22.7 μg/L) (C8HF15O2) underwent partial defluorination and was subsequently biodegraded into perfluoroheptanoic acid (C7HF13O2), perfluorohexanoic acid (C6HF11O2), perfluoropentanoic acid (C5HF9O2), and perfluorobutyric acid (C4HF7O2) in that order (Fig. 6B). These results suggest that partial biodegradation of PFOA occurs through complex biochemical pathways, potentially involving degradation by redox enzymes and ROS within algal cells [30].Notably, in that previous study, no evidence was found to support the biodegradation of PFOA, the identification of by-products, and the biotransformation pathways. Information on the removal mechanism of PFOA and the biodegradation pathway by S. quadricauda helps in understanding the bioremediation of PFAS using microorganisms.Fig. 6. Biosorption, bioaccumulation, and biodegradation of PFOA (A), along with identified by-products of PFOA by LC-MS/MS and proposed biodegradation pathways (B) by S. quadricauda. RT: retention time (min); m/z: mass to charge ratio.3.3. PFOA removal mechanism and proposed biotransformation pathwayTo elucidate the removal mechanism of PFOA, the contents of biosorbed and bioaccumulated PFOA by S. quadricauda were quantified. S. quadricauda achieved a removal efficiency of 58.2% at 5 ppm of PFOA (Fig. 4), with approximately 12.8% of PFOA biosorbed and 45.4% bioaccumulated (Fig. 6 A). LC-MS/MS analysis confirmed that a fraction of the bioaccumulated PFOA (C8HF15O2) underwent partial defluorination and was subsequently biotransformed into perfluoroheptanoic acid (C7HF13O2), perfluorohexanoic acid (C6HF11O2), perfluoropentanoic acid (C5HF9O2), and perfluorobutyric acid (C4HF7O2) in that order (Fig. 6B). To ensure analytical quality, method blanks and baseline controls were analyzed, confirming that all detected biotransformed by-products were completely absent before the initiation of the experiment. Although evidence of defluorination remained limited due to the lack of fluoride release or total fluorine mass balance data, the biotransformation of PFOA by the microalgae was confirmed by identifying valid by-products via LC-MS/MS. However, this approach yielded only tentative candidate-level identification, underscoring the need for definitive, validated quantitative analysis in future studies. These results suggest that partial biotransformation of PFOA occurs through complex biochemical pathways, potentially involving degradation by redox enzymes and ROS within algal cells [30].Notably, in that previous study, no evidence was found to support the biotransformation of PFOA, the identification of by-products, or their underlying pathways. Information on the removal mechanism of PFOA and the biotransformation pathway by S. quadricauda helps in understanding the bioremediation of PFAS using microorganisms.Fig. 6. Biosorption, bioaccumulation, and residual distribution of PFOA (A), and qualitatively identified PFOA by-products via LC-MS/MS with proposed biotransformation pathways (B) by S. quadricauda. RT: retention time (min); m/z: mass-to-charge ratio.3.4. Transcriptomic analysis of S. quadricauda exposed to PFOA (table presented) Conclusions (table presented) 10)Environmental implication (table presented)