A hybrid cellulose nano-crystals cyanobacterial living material improves soil crust rehabilitation

Degraded soils in arid and semi-arid regions face growing threats from erosion and water scarcity, necessitating new strategies for rehabilitation. Biological soil crusts (biocrusts), play a critical role in stabilizing topsoil and enhancing soil function. In this study, we developed a hybrid living material by combining cellulose nano-crystals (CNC) with the desert cyanobacterium Leptolyngbya ohadii, aiming to accelerate and strengthen biocrust formation. The CNC matrix improved the dispersion and reduced the aggregation of cyanobacteria in suspension, promoting a 42 % increase in dry biomass and a 34 % increase in chlorophyll content over 6 days. When applied to sand, the CNC-cyanobacteria hybrid maintained photosynthetic activity (Fv/Fm = 0.4–0.45) suggesting successful application to the soil. Mechanical testing showed that the incubated hybrid material (ICCB) increased soil crust strength to 27 ± 4 N and enhanced tensile strength to 79 ± 8 MPa in standalone films, significantly outperforming CNC alone. Wind tunnel experiments revealed over 75 % reduction in soil erosion, and moisture retention improved to 36 ± 5 % after 4 days, compared to 11 ± 3 % in control soils. Field experiment further validated sustained photosynthetic activity and a 33 % increase in soil carbohydrate content over 25 days post-application. Together, these findings demonstrate that the CNC-Cyanobacteria hybrid promotes robust, photosynthetically active biocrusts and offers a biodegradable, low-cost strategy for soil stabilization and restoration in arid environments.