Studies on Nitrogen Fixing Blue Green Algae and Mass Cultivation

Abstract

Cyanobacteria or blue green algae (BGA) are ecologically important group of organisms since some forms are capable of fixing atmospheric nitrogen. In the present investigation region specific cyanobacteria were isolated from soil samples of paddy field collected from 20 different sites of Patiala district, Punjab and physico-chemical properties were analysed. The soils were mainly alkaline with electrical conductivity (EC) ranging from 100 to 282 μS, organic carbon ranging from 0.37 to 0.85% whereas total nitrogen ranged from 0.035 to 0.087%, available nitrogen ranged from 1.8 to 7.4 mg/kg and available phosphorus from 2.8 to 19.5 mg/kg. Growth of heterocystous cyanobacteria in terms of dry biomass production (mg/ml) and total nitrogen was studied at different intervals in order to assess the nitrogen fixing potential of cyanobacteria. Total nitrogen was highest in Anabaena variabilis (ARM 441) (0.011%) and dry biomass production was highest in Tolypothrix tenuis (ARM 443) (1.70 mg/ml). Heterocyst frequency also highest in Anabaena variabilis (ARM 441) by 14.9% which was also the case with region specific isolate 6. End point growth yielded maximum chlorophyll content (9.3 μg/ml) in Aulosira fertilissima (ARM 444). Wet biomass production in outdoor algal ponds resulted in an average yield of 1.68 kg/m2 after 7 days, 2.9 kg/m2 after 14 days and 4.8 kg/m2 after 21 days whereas dry biomass production was 0.21 kg/m2 after 7days, 0.59 kg/m2 after 14 days and 0.65 kg/m2 after 21 days during the month of March, 2011.