Date of Award


Degree Type



Chemical and Biomedical Engineering

First Advisor

Belovich, Joanne

Subject Headings

Biomass energy -- Research, Microalgae -- Biotechnology, microalgae, chlorella, nighttime, biomass loss, supplementation, productivity


Microalgae have been proven to be a promising source for the production of biofuel. It has higher oil yield than any other food crop. Oil yield from microalgae is 7 to 13 times higher than the best food crop. There are several issues to be addressed for economic production of biofuel from microalgae. One such issue is cultivation of microalgae. Algae can be cultivated photoautotrophically or heterotrophically. Algae grown photoautotrophically lose up to 35 of the biomass during nighttime. Heterotrophic cultivation of microalgae has been proven to be resulting in faster microalgae production compared to photoautotrophic growth, but requires use of expensive external carbon sources as a supplement. Cultivation of microalgae with cyclic combination of photoautotrophic and heterotrophic growth may be an effective and economical method of micro-algae cultivation combining the advantages of photoautotrophic and heterotrophic growth. Cyclic cultivation of Chlorella was performed to study the effect of nighttime supplementation on nighttime biomass loss and productivity. Results showed increased biomass productivity compared to pure photoautotrophic productivity. As high as 33 g/m2-day, productivity values were reported with 0.5 g/L of glucose supplement concentration during nighttime compared to the control cycle with the productivity value of 4g/m2-day. Statistical analysis suggested productivity valuesincreased with glucose concentration. Bacterial concentration was an order of magnitude lesser than the biomass concentration.Glucose concentration data were collected to calculate the yield coefficient for different supplement concentration. Yield coefficient values up to 0.28gm biomass/gm glucose were achieved with supplement glucose concentration of 0.5 g/L