Production of a biocrust-cyanobacteria strain (Nostoc commune) for large-scale restoration of dryland soils

Abstract

Cyanobacteria colonize the soil surface in deserts where they coexist with other organisms such as mosses, lichens, bacteria, fungi, archaea, and microalgae, in communities known as biocrusts. Cyanobacteria are of interest for dryland restoration due to their capacity for survival under water stress, facilitating succession and influencing soil function recovery. In addition, their large-scale culturing in bioreactors is possible. The aims of this study were to optimize the biomass production of a soil cyanobacterium (Nostoc commune) and determine the feasibility of employing fertilizers instead of chemicals for their production. The suitability of the biomass produced in different culture media for inducing biocrusts was tested by inoculation on sterilized mine substrate and then measuring several soil properties. Results showed that the growth rate of biomass cultured in the fertilizer media (0.43 day−1) was close to the chemical media. After 3 months of incubation in soil the cyanobacteria surface coverage increased up to 36% and there was no difference between soils inoculated with biomass produced in chemical or fertilizer media. As the Mann and Myers medium made with fertilizers promoted the best soil improvements, such as increased soil organic carbon and exopolysaccharide content of 8.9 g kg−1 and 2.2 mg g−1, respectively, a growth model was calculated to optimize its production in this medium for future large-scale restoration. Our results demonstrate that Nostoc commune can be economically produced for improving degraded soils, reducing the cost of the medium by 295 € ha−1.