Self-replicating Biophotoelectrochemistry System for Sustainable CO Methanation

Light-driven biohybrid for phosphorus recovery via struvite biomineralization in tetracycline-laden livestock wastewater

Struvite biomineralization drives phosphate mineralization, playing a critical role in sustaining biogeochemical phosphorus cycling and industrial phosphorus recovery. Phosphorus-rich wastewater, however, frequently contains inhibitory tetracycline that suppresses microbial activity, diminishes recovery efficiency, and accumulates in recovered struvite. Semiconductor-mediated microbial photoelectrochemical process generate photogenerated electrons to stimulate microbial metabolism. Concurrently, photogenerated reactive oxygen species can degrade tetracycline. Despite extensive evidence of TC's inhibitory effects on biomineralization, the development of integrated photoelectrochemical-microbial process for simultaneous tetracycline degradation and phosphorus recovery remains unexplored. We develop a microbial photoelectrochemical system integrating microorganisms with nano-semiconductor materials. Light-activated carbon nitride generates electrons boosting microbial metabolism and holes degrading tetracycline. Coupling carbon nitride with S. oneidensis under illumination doubles biomineralization rates in tetracycline-laden wastewater versus conventional struvite biomineralization. The system achieves near-complete tetracycline degradation within 48 hours and full nitrate reduction. Those efforts achieve simultaneous phosphorus recovery and tetracycline removal from wastewater, converting pollutants into agriculturally viable struvite without pH adjustment. The system establishes an energy-efficient platform for coupled nutrient recovery and water purification, while creating a closed-loop framework for resource regeneration from contaminated wastewater.

Liquid Metal Nanobiohybrids for High-Performance Solar-Driven Methanogenesis via Multi-Interface Engineering

Nanobiohybrids for solar-driven methanogenesis present a promising solution to the global energy crisis. However, conventional semiconductor-based nanobiohybrids face challenges such as limited tunability and poor biocompatibility, leading to undesirable spontaneous electron and proton transfer that compromise their structural stability and CH4 selectivity. Herein, we introduced eutectic gallium-indium alloys (EGaIn), featuring a self-limiting surface oxide layer surrounding the liquid metal core after sonication, integrated with Methanosarcina barkeri (M. b). The well-designed M. b-EGaIn nanobiohybrids exhibited superior performance, achieving a maximum CH4 yield of 455.64±15.99 μmol g-1, long-term stability across four successive 7-day cycles, and remarkable CH4 selectivity of >99 %. These improvements stem from enhanced proton-coupled electron transfer involving hydrogen atoms at the core-shell interface, further facilitated by the elevated expression of hydrogenases at the abiotic-biotic interface. This study provides an insightful concept for nanobiohybrid design through multi-interface engineering, advancing sustainable and scalable CO2-to-biofuel conversion under ambient conditions.

Novel Photoelectron-Assisted Microbial Reduction of Arsenate Driven by Photosensitive Dissolved Organic Matter in Mine Stream Sediments

The microbial reduction of arsenate (As(V)) significantly contributes to arsenic migration in mine stream sediment, primarily driven by heterotrophic microorganisms using dissolved organic matter (DOM) as a carbon source. This study reveals a novel reduction pathway in sediments that photosensitive DOM generates photoelectrons to stimulate diverse nonphototrophic microorganisms to reduce As(V). This microbial photoelectrophic As(V) reduction (PEAsR) was investigated using microcosm incubation, which showed the transfer of photoelectrons from DOM to indigenous sediment microorganisms, thereby leading to a 50% higher microbial reduction rate of As(V). The abundance of two marker genes for As(V) reduction, arrA and arsC, increased substantially, confirming the microbial nature of PEAsR rather than a photoelectrochemical process. Photoelectron ion is unlikely to stimulate photolithoautotrophic growth. Instead, diverse nonphototrophic genera, e.g., Cupriavidus, Sphingopyxis, Mycobacterium, and Bradyrhizobium, spanning 13 orders became enriched by 10-50 folds. Metagenomic binning revealed their genetic potential to mediate the photoelectron-assisted reduction of As(V). These microorganisms contain essential genes involved in respiratory As(V) reduction, detoxification As(V) reduction, dimethyl sulfoxide reductase family, c-type cytochromes, and multiple heavy-metal resistance but lack a complete photosynthesis system. The novel microbial PEAsR pathway offers new insights into the interaction between photoelectron utilization and nonphototrophic As(V)-reducing microorganisms, which may have profound implications for arsenic pollution transportation in mine stream sediment.

Sustainable Conversion of Microplastics to Methane with Ultrahigh Selectivity by a Biotic-Abiotic Hybrid Photocatalytic System

Efficient conversion of microplastics into fuels provides a promising strategy to alleviate environmental pollution and the energy crisis. However, the conventional processes are challenged by low product selectivity and potential secondary pollution. Herein, a biotic-abiotic photocatalytic system is designed by assembling Methanosarcina barkeri (M. b) and carbon dot-functionalized polymeric carbon nitrides (CDPCN), by which biodegradable microplastics-poly(lactic acid) after heat pretreatment can be converted into CH₄ for five successive 24-day cycles with nearly 100 % CH₄ selectivity by the assistance of additional CO₂ . Mechanistic analyses showed that both photooxidation and photoreduction methanogenesis worked simultaneously via the fully utilizing photogenerated holes and electrons without chemical sacrificial quenchers. Further research validated the real-world applicability of M. b-CDPCN for non-biodegradable microplastic-to-CH₄ conversion, offering a new avenue for engineering the plastic reuse.

Solar-driven methanogenesis with ultrahigh selectivity by turning down H2 production at biotic-abiotic interface

Integration of methanogens with semiconductors is an effective approach to sustainable solar-driven methanogenesis. However, the H₂ production rate by semiconductors largely exceeds that of methanogen metabolism, resulting in abundant H₂ as side product. Here, we report that binary metallic active sites (namely, NiCu alloys) are incorporated into the interface between CdS semiconductors and Methanosarcina barkeri. The self-assembled Methanosarcina barkeri-NiCu@CdS exhibits nearly 100% CH₄ selectivity with a quantum yield of 12.41 ± 0.16% under light illumination, which not only exceeds the reported biotic-abiotic hybrid systems but also is superior to most photocatalytic systems. Further investigation reveal that the Ni-Cu-Cu hollow sites in NiCu alloys can directly supply hydrogen atoms and electrons through photocatalysis to the Methanosarcina barkeri for methanogenesis via both extracellular and intracellular hydrogen cycles, effectively turning down the H₂ production. This work provides important insights into the biotic-abiotic hybrid interface, and offers an avenue for engineering the methanogenesis process.