Background: Water scarcity is a pressing global challenge increasingly addressed by advanced desalination that converts seawater into potable water. Reverse osmosis and ultrafiltration dominate because they deliver permeate with very low impurities. Their principal limitation is membrane biofouling, which causes clogging, raises energy, operation, and maintenance costs, and shortens membrane life. Multiple approaches mitigate biofouling—most notably pretreatment trains and engineered surface coatings—but cleaning remains the most decisive remediation pathway. Current practice distinguishes physical, chemical, and biological cleaning. Biological cleaning has gained momentum by exploiting microorganisms that inherently counter biofilms. These strategies include targeted secretion of enzymes and antifouling metabolites, and the application of whole-cell culture supernatants containing the full suite of secreted components. In addition, predatory bacteria can infiltrate established biofilms and eradicate them by lysing prey, thereby accelerating the removal of adherent biomass. Progress across these bio-based approaches signals meaningful advances in fouling control and could substantially improve the efficiency, reliability, and sustainability of desalination facilities. Collectively, they underscore the transformative potential of biological antifouling agents in operational systems. Realizing that potential will require rigorous evaluation of technical performance, long-term stability, compatibility with polyamide membranes, regulatory acceptance, and environmental safety, ultimately alongside scalable production and cost-effective deployment in full-scale plants.

Biofouling refers to the undesirable growth of microorganisms on water-submerged surfaces. Microfouling, the initial state of biofouling, is characterized by aggregates of microbial cells enclosed in a matrix of extracellular polymeric substances (EPSs). In seawater desalination plants, filtration systems, such as reverse-osmosis membranes (ROMs), are affected by microfouling, which decreases their efficiency in obtaining permeate water. The existing chemical and physical treatments are expensive and ineffective; therefore, controlling microfouling on ROMs is a considerable challenge. Thus, new approaches are necessary to improve the current ROM cleaning treatments. This study demonstrates the application of Alteromonas sp. Ni1-LEM supernatant as a cleaning agent for ROMs in a desalination seawater plant in northern Chile (Aguas Antofagasta S.A.), which is responsible for supplying drinking water to the city of Antofagasta. ROMs treated with Altermonas sp. Ni1-LEM supernatant exhibited statistically significant results (p < 0.05) in terms of seawater permeability (Pi), permeability recovery (PR), and the conductivity of permeated water compared with control biofouling ROMs and those treated with the chemical cleaning protocol applied by the Aguas Antofagasta S.A. desalination plant.

The dinoflagellate Prorocentrum triestinum forms high biomass blooms that discolor the water (red tides), which may pose a serious threat to marine fauna and aquaculture exploitations. In this study, the algicidal effect of a bacterial strain (0YLH) belonging to the genus Shewanella was identified and evaluated against P. triestinum. The algicidal effects on the dinoflagellate were observed when P. triestinum was exposed to cell-free supernatant (CFS) from stationary-phase cultures of the 0YLH strain. After 24 h exposure, a remarkable reduction in the photosynthetic efficiency of P. triestinum was achieved (55.9%), suggesting the presence of extracellular bioactive compounds produced by the bacteria with algicidal activity. Furthermore, the CFS exhibited stability and maintained its activity across a wide range of temperatures (20–120 °C) and pH values (3–11). These findings highlight the algicidal potential of the bacterium Shewanella halifaxensis 0YLH as a promising tool for the environmentally friendly biological control of P. triestinum blooms.

Al³⁺-toxicity in acidic soils is among the main abiotic stress factors that generate adverse effects in plant growth; in leaves, it affects several physiological parameters such as photosynthesis and ROS balance, leading to limited crop production. On the other hand, sulfur is a macronutrient that has a key role against oxidative stress and improves plant growth in acidic soils; however, the implication of sulfate nutritional status in the modulation of short-term Al³⁺-toxicity tolerance mechanisms in plant leaves are barely reported. This study is focused on the role of sulfate on the leaf response of an Al³-sensitive perennial ryegrass (Lolium perenne cv. Jumbo) after 48 h of exposure. Lolium perenne cv. Jumbo seeds were cultivated in hydroponic conditions with modified Taylor Foy solutions supplemented with 120, 240, and 360 μM sulfate in the presence or absence of Al³⁺-toxicity. The L. perenne cv. Jumbo leaves were collected after 48 h of Al³⁺-toxicity exposure and processed to evaluate the effects of sulfate on Al³⁺ toxicity, measuring total proteins, mineral uptake, photosynthesis modulation, and ROS defense mechanism activation. The plants exposed to Al³⁺-toxicity and cultivated with a 240 µM sulfate amendment showed a recovery of total proteins and Ca²⁺ and Mg²⁺ concentration levels and a reduction in TBARS, along with no changes in the chlorophyll A/B ratio, gene expression of proteins related to photosynthesis (Rubisco, ChlAbp, and Fered), or ROS defense mechanism (SOD, APX, GR, and CAT) as compared with their respective controls and the other sulfate conditions (120 and 360 µM). The present study demonstrates that adequate sulfate amendments have a key role in regulating the physiological response against the stress caused by Al³⁺ toxicity.