Enhanced hydrogen production by immobilized cyanobacterium Lyngbya perelegans under varying anaerobic conditions

•Study includes H2 production by free and immobilized cells of Lyngbya perelegans.•For immobilization agar and alginate were used.•Cell density, immobilized cell size were studied.•It includes the effect of various gaseous environments on hydrogen production.•Comparative study between free and immobilized cells for maximum H2 production upto 120 h was also done.

Hydrogen (H2) production was studied using a non-heterocystous, filamentous cyanobacterium, Lyngbya perelegans in free and immobilized forms, where cells were incubated under O2 free anaerobic environment with alternate light and dark period (21 h light/3 h dark). For immobilization, agar and alginate systems were taken and it was revealed that hydrogen production was more sustained in alginate trapped cells as compared to agar trapped cells and free cells. Cell density and size of bound cell system were also important parameters influencing H2 production in immobilized systems. The type of gas mixtures sparged for creating anoxic environment in the headspace had a significant influence on H2 production showing methane (CH4) to be most conducive component of the gaseous mixture.