Dr. Alexandr Lukyanov

Immobilization of microalgal cells (MA) on assorted carriers is a widespread approach facilitating harvesting of the biomass, protecting MA from harsh conditions, and improving MA productivity. The immobilized MA are especially suitable for removal of nutrients from wastewater and after bioremediation process the attached MA biomass enriched with N and P can be considered as slow-releasing environment-friendly biofertilizer provided that the carrier is biodegradable and non-toxic.  

The chlorophyte strain Lobosphaera sp. IPPAS C-2047 served as the object in the present work. We tested chitosan-based polycationic polymeric materials obtained by cryopolymerization of chitosan with glutaraldehyde. These carriers which possess a high immobilization efficiency and supported the prolonged cultivation of immobilized MA without impairing their growth and photosynthetic activity. 

Nutrient (nitrate nitrogen, Ni and orthophosphate, Pi) removal capacity of the chitosan-immobilized Lobosphaera cells was significantly higher than that of the suspended cells. The specific removal rates of Pi and Ni by the suspended MA cultivated without cross-linked chitosan polymers comprised 0.6 and 3.2 mg mg-1 Chl d-1, while the chitosan-immobilized MA consumed Pi and Ni at rates 1.3 and 4.5 mg mg-1 Chl d-1, respectively. During the 14-d experiment, the chitosan-based carries demonstrated a high mechanical and biological stability, but after 3 weeks of incubation the signs of polymer biodegradation were observed by electronic microscopy. 

 Collectively, the biodegradable and non-toxic chitosan-based polymers were shown to be environment-friendly materials enhancing the nutrient bioremoval from wastewater by the immobilized microalgae cells.