Enhancement of lipid productivity of Chlorella protothecoides cultivated in secondary wastewater under nitrogen starvation through optimization of environmental factors

ABSTRACT

A lab scale externally illuminated photobioreactor was used to evaluate the lipid productivity (LP) of microalga Chlorella protothecoides (SAG-211-10C) cultivated in municipal secondary waste water supplemented with CO₂. Experiments were conducted in two stages: growth phase (GP) and nitrogen starvation phase (NSP). The influence of five environmental factors (light intensity [LI], photoperiod, temperature, concentration of CO₂, pH) on LP of Chlorella protothecoides under both phases was studied and the parameters were individually optimized. Under optimum operating conditions in GP (LI 6 klux, photoperiod 12 h:12 h, temperature 25°C, 6% concentration of CO₂), the total nitrogen was completely consumed after 8 days of operation and highest LP of 64.7 mg/(L.day) was obtained. This value was further enhanced to 106.65 mg/(L.day) by operating the photobioreactor in NSP under its optimum conditions (LI of 4 klux, photoperiod of 16 h:8 h, temperature 25°C, pH 8, 4% concentration of CO₂). Under optimum operating conditions, removal efficiency of total phosphorous and Chemical Oxygen Demand were 100 and 70.19%, respectively, and highest carbon fixation rate of 549.16 mg CO₂/(L.day) was observed.

KEYWORDS:

• Chlorella protothecoides
• secondary wastewater
• photobioreactor
• nitrogen starvation phase
• lipid productivity
• carbon dioxide fixation

Acknowledgment

This work was supported by the Visveswaraya Technological University, Belagavi, Karnataka, India, under VTU research grant scheme 2010-2011 (VTU /Aca. /2011-12/A-9/6380).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Visveswaraya Technological University, Belagavi, Karnataka, India, under VTU research grant scheme 2010-2011 [grant number VTU /Aca. /2011-12/A-9/6380].