Production Optimization of Desert Soil-Immobilizing Exopolysaccharides in isolated Cyanobacteria of the Central Desert of Iran

Soil immobilization through the improvement of biological soil crust can cause a reduction in dust emission and an increase in soil fertility in desert areas. Terrestrial cyanobacteria play an important role among the microorganisms existing in biological soil crust to synthesize extracellular polysaccharides (EPS) leading to adhere soil particles. Regarding the various environmental factors affecting cyanobacterial EPS production, the aim of this research is to investigate the factors to optimize EPS secretion. The soil, collected from the Yazd desert region was transported to the laboratory. After two weeks of incubation and addition of BBM culture medium to the samples, the grown strains were isolated by the linear culture method and then transferred to the liquid medium. The effects of measurable parameters in the desert environment were then evaluated including temperature (۲۱, ۳۴°C), light period (۱۰, ۱۴ hr), soil salinity (۴, ۶, ۸ μS/m۲) on two types of EPS (released (REPS) and attached to the cell wall (CEPS)). It was founded that both EPSs have been secreted in the highest amount when the cyanobacterial culture was in the stationary phase. The results of the experimental design showed the direct impact of the light period on the production of polysaccharides so that the ۱۴-hr period produced more polysaccharides. Moreover, it was indicated that the most significant effect was the light period while soil salinity had the least effect. Based on the result, a successful method of inoculating cyanobacteria in the soil can be obtained by optimizing the affecting parameters to determine the time for more efficent inoculation of the soil in the field studies.

Keywords:

Soil Immobilization , Polysaccharide , Cyanobacteria , Temperature , Salinity , Light Period.