Bioresource Technology最新文献

Algae-based carbon capture and utilization (CCU) technique offers a sustainable strategy for CO₂ mitigation, but its efficiency is often limited by poor gas-liquid mass transfer and unstable carbon availability. Here, this study developed an iron oxide nanoparticle (Fe₂O₃NPs)-incorporated electrospun nanofiber membrane to enhance CO₂ capture and microalgal fixation. Results revealed that the Fe₂O₃NPs was able to reduce fiber diameter, refine pore architecture, and increase specific surface area, thereby the improved CO₂ adsorption. In Chlorella cultivation, the final biomass concentration and CO₂ biofixation rate of modified membrane increased by respective 11.6%±1.2% and 14.3% compared with that of pristine nanofibers. Furthermore, the modified membrane significantly promoted the early-stage biofilm formation, yielding biofilms that were 47.9% thicker, denser, and exhibited increased rougher surface. Nanoparticle-induced "microhooks", together with enhanced EPS secretion, strengthened algal attachment, increased cell density, and improved spatial homogeneity, thus creating a favorable microenvironment for rapid biofilm development. Cellular analyses demonstrated that membranes modified with Fe₂O₃NPs increased intracellular ATP by 45.6%, superoxide dismutase activity by 39.9%, and specific growth rate by 41.8% compared to the blank controls, indicating enhanced metabolic activity and stress resistance. Physicochemical characterization further showed that a reduction in electrostatic repulsion and an increase in hydrophobicity. Meanwhile, Lifshitz-van der Waals (U^LW) and Lewis acid-base (U^AB) interaction energies increased by approximately twofold and 2.74-fold, respectively. These changes synergistically enhanced initial algal adhesion and attachment stability, facilitating CO₂ enrichment. In summary, this work elucidates the synergistic bio-physicochemical mechanisms underlying nanoparticle-modified membranes and specify their potential for advancing efficient microalgae-based CCUS technologies.

Microalgae biorefinery is limited by energy-intensive harvesting. Inspired by fungal self-pelletization, this study explored thermoresponsive polymers (TRPs) for microalgae harvesting. The lower critical solution temperature (LCST) of TRPs in cultivation media was significantly lower than that in water, facilitating temperature-induced phase separation. Harvesting efficiency depends on TRP molecular weight (MW), concentration, and algal species (size, medium, cell wall composition). PNIPAM-300  kDa achieved > 90% efficiency for Nannochloropsis oculata, a seawater microalga whose glucosamine-rich cell walls could partly explain its pronounced MW sensitivity. Introducing cationic groups (e.g., allylamine) reduced efficiency, suggesting a physical entrapment mechanism rather than charge-based flocculation. After harvesting, all tested microalgae species consistently exhibited wrinkled walls, dimmed chlorophyll fluorescence, and reduced viability, suggesting that TRP processing could facilitate intracellular product release. This TRP-induced method enables rapid harvesting with potential downstream advantages, marking a step toward sustainable microalgae processing.

Low temperature is a major constraint on the practical application of anaerobic ammonium oxidation (anammox). Although biochar has been reported to improve low-temperature anammox, the effect of dosage remains insufficiently understood. In this study, mature anammox sludge was amended with 0, 3, 7, and 9 g/L bamboo-derived biochar and operated under a stepwise temperature decrease from 35 to 15°C, followed by low-temperature operation for 70 d. Reactor performance, extracellular polymeric substances (EPS), microbial community composition, and metagenomic functional potential were analyzed to clarify the dose effect of biochar. Among the tested dosages, 7 g/L biochar achieved the highest nitrogen removal efficiency (48.6%) at 15°C, which was 12.8 percentage points higher than the control value of 35.8%. Biochar-amended reactors also showed higher EPS contents than the control, and the 7 g/L group better maintained the PN/PS ratio under low-temperature stress. Community analysis indicated a higher relative abundance of Candidatus Brocadia in the biochar-amended groups, especially at 7 g/L. Metagenomic analysis further showed higher abundance of genes associated with nitrogen metabolism, carbon metabolism, and EPS-related precursor synthesis in the 7 g/L group. These results suggest that an appropriate biochar dosage can improve low-temperature anammox performance and is associated with EPS stabilization, enrichment of key functional taxa, and enhanced functional potential. This study provides guidance for biochar dosage optimization in low-temperature anammox systems.

The bioconversion of CO₂‑derived methanol into higher‑value chemicals offers an attractive route for hybrid catalytic-biotechnological carbon capture and utilization (CCU). Clostridium luticellarii is one of the few acetogens able to produce isobutyric acid. However, operational and metabolic factors driving its production are poorly understood. This work investigates how CO₂ availability shapes the product spectrum of C. luticellarii during methylotrophic growth and assesses whether CO₂ supply can be used as a process lever to promote isobutyric acid formation. Batch experiments with varying initial bicarbonate concentrations revealed that conditions leading to CO₂ limitation (i.e., DIC depletion at ≤ 30 mM NaHCO₃) redirected carbon and electron fluxes away from acetic acid toward butyric and isobutyric acids, with the latter accounting for up to 41% of total products. This metabolic switch was not observed when CO₂ was in excess (>45 mM). High acetic acid supplementation (100 mM) triggered isobutyric acid production even while CO₂ was still available, indicating a combined regulation of dissolved inorganic carbon (DIC) and acetic acid availability. Net acetic acid consumption took place in all isobutyric acid-producing experiments. These observations were reproduced in 3-L bioreactors and further exploited through a fed‑batch strategy in which an initial acetic‑acid‑accumulating phase was followed by CO₂‑limited feeding. This approach achieved complete conversion of methanol and CO₂ and yielded an isobutyric acid titer of 2.70 ± 0.04 g·L^-1. Controlling CO₂ availability is a viable operational tool to steer C. luticellarii metabolism toward isobutyric acid production, in interaction with electron acceptor availability.

Bisphenols (BPA, BPF and BPS) are emerging contaminants with well-documented endocrine-disrupting effects, and their environmental occurrence often coincides with heavy metals and microplastics. In this study, a three-dimensional chitosan/bentonite composite foam (CBF) was fabricated via directional ice-templating and systematically evaluated as a recoverable adsorbent for bisphenols. The CBF exhibited stable adsorption performance, with kinetics following the pseudo-second-order model and isotherms well described by the Langmuir model, achieving moderate maximum capacities of 13.69 to 16.27 mg/g under a monolithic, manually recoverable design. High removal efficiencies were maintained over a wide pH range (2.0-10.0) and under varying ionic strength conditions. Spectroscopic and thermodynamic analyses indicate that bisphenol adsorption is governed by hydrogen bonding, polar interactions, and pore confinement effects, with selectivity among analogues modulated by their analogue-specific interaction pathways with the functional groups of CBF. The positive enthalpy change and increasingly negative Gibbs free energy further support a spontaneous and endothermic adsorption process. Preliminary tests further indicated that the macroporous framework was capable of capturing heavy metal ions (Pb(II), Cd(II)) and physically entrapping representative microplastics (PLA, PS, PE), suggesting potential applicability beyond bisphenols. Within its intended design scope of prioritizing operational simplicity over maximum capacity, CBF offers a monolithic platform with facile manual separation and minimal secondary turbidity. This combination of low-cost raw materials, monolithic recoverability, and multi-class pollutant applicability distinguishes CBF from conventional powdered adsorbents and is relevant to the practical treatment of bisphenol contaminated water under complex matrix conditions.

Lycopene is a high-value antioxidant, yet its microbial production is often limited by inefficient cis-trans isomerization steps in heterologous carotenoid pathways. This study systematically compared two key carotenoid isomerases, ZISO and CRTISO, from Dunaliella salina (Ds) and Dunaliella bardawil (Db). Molecular docking and dynamic simulations revealed that DbZISO exhibited superior substrate binding (binding energy: -13.09 kcal/mol) and conformational stability, whereas DsCRTISO showed higher catalytic efficiency toward 7,7',9,9'-tetra-cis-lycopene than DbCRTISO. Based on these results, Dbziso and Dscrtiso were co-expressed in E. coli to generate the recombinant strain DsZC. After single-factor and response surface methodology (RSM) optimization, DsZC produced 1.56 ± 0.06 mg/g DCW all-trans-lycopene under the optimized conditions (0.48 mM IPTG, 27.7 °C, 0.3 mM δ-ALA, 48 h), representing a 1.24-fold increase over the native DsCRT pathway. This study demonstrates that cross-species combination of optimally performing isomerases is an effective strategy to boost lycopene biosynthesis, offering a viable platform for industrial carotenoid production.

Dissimilatory nitrate reduction to ammonium (DNRA) is important for nitrogen conservation and resource recovery in wastewater treatment, but its efficiency is often limited by competition for electrons and substrates from denitrifiers. Although hydroxylamine (NH₂OH) has been shown to modulate various nitrogen transformation processes, its long-term effects on DNRA systems and the underlying microbial ecological responses remain unclear. In this study, the nitrogen transformation performance, electron transfer characteristics, and microbial community succession in DNRA systems were comprehensively investigated under prolonged exposure to 0-5 mg/L NH₂OH. The results demonstrated that, with increasing NH₂OH concentrations, the system consistently achieved near-complete nitrate removal without nitrite accumulation, and the effluent NH₄⁺-N reached up to 51.5 mg/L, indicating a substantial enhancement of DNRA ammonium production. Functional activity analyses and apparent electron-equivalent balance suggested an increased contribution of DNRA to nitrate-reduction-associated electron consumption. Metagenomic analyses further showed that NH₂OH could decrease the relative abundances of denitrification-related genes, including nirS, norB, and nosZ, while increasing those of narG and the nrf gene cluster. Building upon the existing DNRA functionality, NH₂OH selectively enriched a tolerant DNRA population, exemplified by Ignavibacteriota, and facilitated cross-feeding interactions and electron transfer network remodeling involving fermentative bacteria. Collectively, these findings suggest that NH₂OH can weaken denitrification competition and increase the apparent contribution of DNRA to nitrate-reduction-associated electron consumption, thereby enhancing ammonium production. Moreover, these findings may provide a theoretical basis for the future development of DNRA-Anammox coupled processes for high-level nitrogen removal.