Tandem biocatalysis in synthetic microbial consortium: efficient polybutylene adipate terephthalate degradation coupled to polyhydroxybutyrate synthesis.
Polybutylene adipate terephthalate (PBAT) is prone to incomplete degradation, leading to environmental pollution and carbon resource waste. Biodegradation and valorization of waste plastics are essential for addressing plastic pollution and promoting a circular economy. Enzymatic degradation offers advantages, but free enzymes suffer from low stability and poor recyclability. Here, surface display technology was used to construct a cutinase Tfcut-DM display system in Escherichia coli BL21(DE3). The results showed that surface display significantly enhanced the stability and reusability of Tfcut-DM. Compared with free enzymes, its thermostability and pH stability increased by 11.9-fold and 42.1-fold, respectively, and approximately 80% of initial activity was retained after seven reuse cycles. Under optimized conditions, the surface-displayed strain released 255.9 µM of terephthalic acid (TPA) from PBAT films over 5 days, with near-complete degradation. To enable TPA valorization , the tph operon was introduced to C. necator H16 (CnH16-tph) for TPA-to-PHB conversion. A co-culture system comprising the surface-displayed strain and CnH16-tph was established for proof-of-concept one-pot conversion of PBAT to PHB. PHB accumulation is indirectly attributed to the TPA derived from PBAT degradation. Under optimized conditions, the maximum PHB yield reached 0.91 g/L. While isotopic tracing would be required for definitive carbon flux assignment, this indirect evidence strongly suggests the successful conversion of PBAT-derived TPA to PHB. This study provides a novel approach for the green degradation and resource utilization of waste PBAT, facilitating the recycling of discarded resources.
Polybutylene adipate terephthalate (PBAT) is a widely used biodegradable plastic, but its microbial degradation mechanisms and environmental responses remain poorly understood. In this study, two compost inocula (K and I) were used to establish PBAT enrichment cultures under mesophilic (35 °C, M) and thermophilic (58 °C, T) conditions, and the effects of temperature and inoculum source on bacterial community structure and PICRUSt2-derived predicted functional profiles were investigated. Surface analyses revealed cracking, erosion, and structural collapse of PBAT under all conditions, with more pronounced degradation in compost I-derived cultures. Microbial diversity decreased during enrichment, accompanied by dominance of specific genera. Under mesophilic conditions, Pseudoxanthomonas dominated (72.6%–91.0%) and showed strong positive correlations with predicted ester bond hydrolysis-related KOs (p < 0.05), suggesting a potential association with initial hydrolysis. Under thermophilic conditions, compost K cultures were dominated by Thermoflavifilum and Rhodothermus, which were mainly associated with predicted hydrolysis-related KOs, whereas compost I cultures were dominated by Thermoflavifilum and Thermopolyspora and showed stronger associations with predicted KOs related to adipate and terephthalic acid metabolism. Predicted aromatic intermediate metabolism-related KOs, including K04101, K01055, and K01607, were also higher in compost I-derived thermophilic cultures. Overall, temperature and inoculum composition jointly shaped bacterial community assembly and predicted PBAT degradation-related functional potential. Thermophilic conditions combined with compost I were associated with functionally differentiated bacterial communities and higher predicted potential for downstream PBAT-derived intermediate metabolism. These findings provide a microbial ecological basis for temperature- and inoculum-guided enrichment strategies to improve PBAT biodegradation and biodegradable plastic waste treatment.
Subin Hwang, Soo-Ye-On Lee, K. Cho· Journal of Polymers and the...· 0 citations
Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable plastic with enhanced mechanical properties, which can serve as a substitute for conventional plastics. However, the monomers released during its biodegradation, such as adipic acid (AA), 1,4-butanediol (1,4-BDO), and terephthalic acid (TPA), accumulate into the environment or are not simply consumed through central metabolism, limiting their resource value. Therefore, designing a single strain that can efficiently consume all monomers is challenging. Here, a consortium comprising Pseudomonas putida KT2440 harboring tpaK, tphA, and tphB which metabolizes 1,4-BDO and TPA and Cupriavidus necator H16, which converts AA into polyhydroxybutyate (PHB) via β-oxidation was constructed to convert all PBAT-derived monomers into PHB. To enhance polyhydroxyalkanoate production, a levulinic acid (LA)-producing strain GP101 was added to the consortium, resulting in 0.75 g/L PHB and 0.20 g/L 4-hydroxybutyrate (4HB) production and representing a 6.25-fold increase in PHB production compared to that by the consortium containing P. putida KT2440 that could not produce LA. Optimizing the strain ratio of P. putida KT2440 GP101 to C. necator H16 to 2:1 resulted in maximum production of 0.98 g/L PHB and 0.52 g/L 4HB, and all PBAT-derived monomers were completely disappeared within 30 h. This is the first study to demonstrate complete utilization of PBAT monomers and valorization into PHB by an LA-mediated microbial consortium. This approach reveals controllable and reproducible consortia beyond the complex design of a single strain and simple treatment of each monomer, demonstrating the feasibility of converting PBAT-derived monomers into value-added products.
Gaeun Lim, Yunhee Jeong, Seung Hun Lee et al.· ACS Synthetic Biology· 0 citations
γ-Hexachlorocyclohexane (γ-HCH), a typical persistent organic pollutant, exhibits strong soil adsorption and low bioaccessibility, which limit its microbial degradation efficiency. Cyclodextrins (CDs) are environmentally friendly, biodegradable compounds with hydrophobic cavities that show potential for pollution remediation; However, their multiple roles in anaerobic γ-HCH degradation remain unclear. This study investigated the effects of α-CD and β-CD as solubilizers, carbon sources, and potential electron donors on the anaerobic biodegradation of γ-HCH in liquid and soil-liquid mixed culture systems. Results indicated that in soil-containing system, CDs, especially β-CD, significantly enhanced the bioaccessibility of γ-HCH through inclusion complexation, promoting the accumulation of benzene and chlorobenzene during early degradation stages. Simultaneously, CDs served as utilizable carbon sources, supporting the growth and metabolism of dechlorinating functional bacteria (e.g., Clostridium). However, CDs could not replace direct electron donors such as hydrogen in driving reductive dechlorination. Structural differences between CDs influenced their efficacy: β-CD, with its larger cavity, showed superior solubilization of γ-HCH, while α-CD exhibited stronger inclusion affinity for degradation intermediates (benzene and chlorobenzene), altering their accumulation profiles. This study systematically clarifies the dual mechanisms and structure-dependent effects of CDs in anaerobic bioremediation of γ-HCH, providing a theoretical basis for developing targeted and green CD-based remediation strategies.
Microbial polyhydroxyalkanoates (PHAs) have drawn increasing attention as sustainable alternatives to conventional plastics. However, PHA market growth remains limited because of their elevated production costs. To address this challenge, this study investigated the valorization of food waste as a low-cost feedstock and the combination of yeast extract and nitrogen-rich waste as a co-nitrogen source for sustainable poly(3-hydroxybutyrate) (PHB) production by extremely halophilic archaeon Haloarcula sp. PLQ. Implementation of this strategy resulted in the production of 1.099 ± 0.205 g L-1 of biomass with a PHB concentration of 0.634 ± 0.0063 g L-1, corresponding to a gravimetric PHB content of approximately 60 ± 11.755% of its cell dry weight (CDW). However, the strain achieved a lower PHB content as determined by gas chromatography analysis (GC) of approximately 27.87 ± 0.067% of its CDW, which may be related to the co-extraction of non-PHB cellular components during gravimetric determination. Regarding the characterization of PHB film, the SEM-EDS analysis revealed a porous and heterogeneous surface morphology that was composed of approximately 56.38 wt% carbon and 35.27 wt% oxygen with minor amounts of sodium, chlorine, and magnesium. Regarding FTIR and Raman spectroscopy analyses, the functional groups were found to be similar to those of commercial PHB. The XRD pattern was also similar to that of pure PHB. TGA and DSC results confirmed that the film is a semi-crystalline polymer-based material, with a degree of crystallinity of 61.3%, as determined from the first DSC heating scan. The melting point and the maximum degradation temperature of PHB were found to be 157.3 and 293.35 °C, respectively. This present study demonstrates the potential of the haloarchaeal strain for converting carbon- and nitrogen-rich waste streams into biodegradable PHB, aligning with circular bioeconomy principles.
Manel Ben Abdallah, K. K. Sadasivuni, M. Cherif et al.· Journal of Environmental Man...· 0 citations
Overall, ZY1 and G1B exhibited overlapping functions with relative functional differences and potential complementarity, supporting the use of synthetic microbial consortia to enhance PET depolymerization and downstream product conversion.
Jiarong Qiu, Yufeng Jin, Liang-Qing Zhang et al.· Journal of Environmental Man...· 0 citations
Reframing plastic degradation as a multi-scale, designable system rather than a single-enzyme process highlights opportunities for coupling protein engineering with controlled deployment, including biofilm-based localization and metabolic pathway integration, to enable more effective and environmentally relevant microplastic remediation.
Debashrita Majumder, Anushree Dutta, D. Lahiri et al.· Preparative Biochemistry & B...· 0 citations