Effects of parameters affecting biomass yield and thermal behaviour of Chlorella vulgaris

Conventional fossil fuels are facing a global challenge which lead scientists to explore alternative fuel production from biological sources. The algae-based fuels are gaining rapid attention as it has potential to replace petroleum-based fuels. An indigenous high lipid producing microalgae was isolated from a freshwater pond in the KwaZulu-Natal province of South Africa. The isolate was later identified as Chlorella vulgaris, based on partial 28S large subunit ribosomal RNA gene sequence. The growth kinetics, pyrolytic characteristics and photosynthetic efficiency of Chlorella was evaluated in vitro. The optimized conditions for higher biomass yield of the selected strain were at 4% CO2, 0.5 g l− 1 NO3 and 0.04 g l− 1 PO4, respectively. The pulse amplitude modulation results indicated that C. vulgaris could withstand a light intensity ranging from 150 to 350 μmol photons m− 2 s− 1. Further increase in light intensity resulted in a decline of the electron transport rate. Carbon fixation rate, lipid content and calorific value of C. vulgaris was 6.17 mg l− 1 h− 1, 21% and 17.44 kJ g− 1, respectively. The pyrolitic studies under inert atmosphere at different heating rates of 15, 30, 40 and 50°C min− 1 from ambient temperature to 800°C showed that the overall final weight loss recorded for the four different heating rates was in the range of 78.9–81%. These studies could be useful to appraise the biofuel potential of the isolated C. vulgaris strain, which can later be taken for pilot scale production.