Date of Award

2014

Degree Type

Thesis

Department

Chemical and Biomedical Engineering

First Advisor

Belovich, Joanne M.

Subject Headings

Biomass energy -- Research, Algal biofuels, Microalgae -- Biotechnology, Scenedesmus, Bioreactors

Abstract

The need for renewable sources of energy has become critical as fossil fuel resources, which include oil, coal, and natural gas, are known to contribute to climate change and will eventually be depleted. Biofuels that originate from the fat of plants, animals, microalgae, and bacteria are an attractive alternative. Microalgae, in particular, are strong candidates for biofuel production since they have a high growth rate and lipid content (up to 50 in some species). The goal of this research was to optimize 3N-BBM+V recipe (Bold Basal Medium with 3-fold Nitrogen and Vitamins) in an effort of reducing the amount of nutrients used in growing the green microalgae Scenedesmus dimorphus, and hence lower the cost of cultivation. Three runs were carried out on a 5L bioreactor in batch mode. The average growth rate of S. dimorphus was 0.17 ± 0.03 days-1. Inductively Coupled Plasma was utilized to monitor substrate concentration with time in the bioreactor which allowed the determination of yield coefficients in gdw biomass/g substrate for magnesium (253±50), calcium (341±84), potassium (61±15), phosphorous (60±13), and iron (5807±3000). These yields were utilized to calculate the optimal starting substrate concentration in the media in mg/L for magnesium (4.3±0.3), calcium (3.2±0.2), potassium (18±1), phosphorous (18±1), and iron (0.19±0.015). The inverse of mass fraction for elements in the biomass was obtained in gdw biomass/g substrate for magnesium (309±9), calcium (341±84), potassium (98±6), phosphorous (70±5), and iron (8075±2500). The average substrate consumption rates in the three runs for Mg, Ca, Fe, P, and K are 0.61±0.41,0.31±0.64, 0.008±0.03, 2.8±1.6, and 1.3±2.2 mg substrate/gdw biomass.day respectively. Potassium and phosphorous have the lowest yields which is consistent wit h them having the highest consumption rates. The bead beater and mortar and pestle cell lysing methods were utilized to determine which i

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