059 | Marine cyanobacterial biomasses as biocompatible soil-wetting and water-retention agents

Angela Macrì^1|2, Vincenzo Zammuto^1|2, Alice Restifo Chiavetta¹, Antonio Ficara¹, Erminia Conti³, Diego Leone³, Patrizia Trifilò¹, Maria Teresa Caccamo^2|4, Salvatore Magazù^2|4, Concetta Gugliandolo^1|2 | ¹Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy; ²University of Messina, Research Centre for Extreme Environments and Extremophiles, Messina, Italy; ³Department of Biological, Geological and Environmental Sciences, University of Catania, Italy; ⁴Department of Mathematical and Computer Sciences, Physical and Earth Sciences, University of Messina, Italy.

Climate change is having various effects on water availability, severely compromising agriculture productivity. In arid and semiarid soils, water scarcity can form a water-repellent barrier that prevents water infiltration and retention. To explore novel wetting and humectant agents, we studied the hydrating capabilities of the biomass (BC) of two marine filamentous cyanobacteria, Kamptonema okenii and Leptolyngbya sp., isolated from the Strait of Messina (Italy) (BC1 and BC2, respectively). Specifically, we evaluated their following characteristics: i) wetting properties, measuring the reduction in water contact angle (θ); ii) moisture uptake capacity, iii) water retention rate in soil subjected to high-solar irradiance (1367 W m⁻²), and iv) molecular structural dynamics hydration (water content from 0 to 160% w/w), using Attenuated Total Reflectance–Fourier Transform InfraRed spectroscopy. The two biomasses differed in their chemical structure: the carbohydrate component was more abundant in BC2, while the peptide component was more abundant in BC1, and consequently, they showed different hydrating capacities and toxic effects. BC2 exhibited the best hydrating performance, being the best wetting agent (θ = 49°) and the most effective humectant agent, absorbing atmospheric moisture (31%) after 6h. The molecular dynamics of hydration confirmed the greater ability of BC2 to capture liquid water (80% saturation) compared to BC1 (60%). When added to soil, BC2 (1 mg g⁻¹) retained water (18.1%) more efficiently than BC1 (12%), under high-light irradiance. Furthermore, the addition of BC2 to soil (0.1%, w w⁻¹) increased the water content available to vegetation (4.11 g g⁻¹) compared to BC1 (3.87), as resulted by potentiometric analyses. Both biomasses did not inhibit the Vibrio harveyi bioluminescence up to 1 mg mL⁻¹, nor they did show acute effects on the viability of the beneficial entomopathogenic nematode Steinernema feltiae TP-LP10, up to a concentration of 10 mg mL⁻¹. However, BC1 showed moderate chronic toxicity (36% mortality) after 48h of treatment. As a not-toxic wetting and humectant agent, BC2 can be considered an eco-sustainable alternative to industrially produced soil improvers, used as additives to counteract soil dehydration.
This work was supported by PRIN-2022 PNRR “SeaForSoil” CUP J53D23018450001 -P2022M7S2J.