Natural AIEgens as Ultraviolet Sunscreens and Photosynergists for Solar Fuel Production.

Bio-nano hybrids (BNH), combining semiconductors and microorganisms, have shown great promise for effective solar-to-fuel energy conversion. However, the high-energy ultraviolet (UV) photons in the solar spectrum can cause severe photocorrosion of semiconductors and irreversible photodamage to microorganisms within BNH. Here, we developed an encapsulation strategy using natural luminogens with aggregation-induced emission characteristics (AIEgens) to construct a protective layer for BNH, effectively shielding them against high-energy UV photons. We incorporated natural berberine (BBR) into the BNH composed of Methanosarcina barkeri and polymeric carbon nitrides (CNx). The self-assembled BNH-BBR system displayed a 2.75-fold higher CH4 yield than BNH under simulated solar irradiation. Mechanism analysis revealed that BBR acted as a UV sunscreen for BNH by converting high-energy short wavelengths into low-energy long wavelengths, thereby reducing the accumulation of reactive oxygen species and alleviating the photocorrosion of CNx. Furthermore, BBR functioned as a photosynergist for BNH by regulating photoelectron production and utilization, enhancing the intracellular energy formation in M. barkeri for growth and metabolism. This work provides important insights into the effective and scalable conversion of CO2 into valuable biofuels with BNH under light illumination containing high-energy photons.

Methanogenesis in the presence of oxygenic photosynthetic bacteria may contribute to global methane cycle.

Accumulating evidences are challenging the paradigm that methane in surface water primarily stems from the anaerobic transformation of organic matters. Yet, the contribution of oxygenic photosynthetic bacteria, a dominant species in surface water, to methane production remains unclear. Here we show methanogenesis triggered by the interaction between oxygenic photosynthetic bacteria and anaerobic methanogenic archaea. By introducing cyanobacterium Synechocystis PCC6803 and methanogenic archaea Methanosarcina barkeri with the redox cycling of iron, CH4 production was induced in coculture biofilms through both syntrophic methanogenesis (under anoxic conditions in darkness) and abiotic methanogenesis (under oxic conditions in illumination) during the periodic dark-light cycles. We have further demonstrated CH4 production by other model oxygenic photosynthetic bacteria from various phyla, in conjunction with different anaerobic methanogenic archaea exhibiting diverse energy conservation modes, as well as various common Fe-species. These findings have revealed an unexpected link between oxygenic photosynthesis and methanogenesis and would advance our understanding of photosynthetic bacteria's ecological role in the global CH4 cycle. Such light-driven methanogenesis may be widely present in nature.

Towards effective recovery of humate as green fertilizer from landfill leachate concentrate by electro-neutral nanofiltration membrane.

Under the environmental sustainability concept, landfill leachate concentrate can be up-cycled as a useful resource. Practical strategy for effective management of landfill leachate concentrate is to recover the existing humate as fertilizer purpose for plant growth. Herein, we designed an electro-neutral nanofiltration membrane to separate the humate and inorganic salts for achieving a sufficient humate recovery from leachate concentrate. The electro-neutral nanofiltration membrane yielded a high retention of humate (96.54 %) with an extremely low salt rejection (3.47 %), tremendously outperforming the state-of-the-art nanofiltration membranes and exhibiting superior promise in fractionation of humate and inorganic salts. With implementation of the pressure-driven concentration process, the electro-neutral nanofiltration membrane enriched the humate from 1756 to 51,466 mg∙L-1 at a fold of 32.6, enabling 90.0 % humate recovery and 96.4 % desalination efficiency from landfill leachate concentrate. Furthermore, the recovered humate not only exerted no phytotoxicity, but also significantly promoted the metabolism of red bean plants, serving as an effective green fertilizer. The study provides a conceptual and technical platform using high-performance electro-neutral nanofiltration membranes to extract the humate as a promising nutrient for fertilizer application, in view of sustainable landfill leachate concentrate treatment.