Physiological and biochemical responses of the green alga Pachycladella chodatii (SAG 2087) to sodicity stress

The effects of various concentrations of different carbon sources (Na2CO3 and NaHCO3) as sodicity stress on growth parameters, CO2 consumption rate, enzyme activity, intracellular lipid content, and fatty acid profiles of Pachycladella chodatii were studied. Generally, the total chlorophyll was increased by increasing the concentrations of Na2CO3 and NaHCO3. The biomass productivity as well consumption rate of carbon dioxide of P. chodatii reached the highest values with increasing concentrations of Na2CO3 and NaHCO3. The soluble protein content of P. chodatii was highest at the lowest Na2CO3 and NaHCO3 concentrations. The addition of different concentrations of Na2CO3 and NaHCO3 in the growth media induces lipoxygenase and superoxide dismutase specific activity. Catalase and total antioxidant enzymes were increased by supplementing the growth media with 60 and 45 mg l−1 of Na2CO3 and NaHCO3, respectively. Hydrogenase uptake activity in P. chodatii increased gradually in all treated cultures with the time elapsed recording the maximum activity after 11 days of growth especially at 60, 45 mg l−1 of Na2CO3 and NaHCO3 respectively. Lipids content was increased at low concentration of Na2CO3 (40 and 15 mg l−1) and NaHCO3 (60, 45 mg l−1) respectively. Subsequent to algal cultivation in different concentrations of Na2CO3, the cultures were filtered and biodiesel was prepared by direct esterification of dry algal biomass. Methyl esters of palmitic, elaidic and stearic acids represented the major components while myristic, pentadecanoic and 9,12-octadecenoic acids represented a minor component of biodiesel produced from P. chodatii treated with different concentrations of Na2CO3 and NaHCO3.