1. Optimizing Algae Growth and Lipid Accumulation for Biofuel Production Brittany Schier1, Laura Chavez2, Mauricio Pena2, Giovanina Hinojosa2, Andy Ly2, Evelyn Garcia2  Mentors: Dr. Krystel Castillo1, Dr. Michael Persans2, Dr. Hudson DeYoe2 1The University of Texas at San Antonio, One UTSA Circle, San Antonio TX USA 2University of Texas - Rio Grande Valley, 1201 W University, Edinburg, TX USA
Abstract
Two green microalgae Nannochloris sp. and Oocystis sp. were grown in varying salinity and sucrose environments to determine the optimal growing conditions through statistical design and analysis of experiments. The best conditions to maximize absorbance were identified.
1. Introduction
Algal biofuels may be used as diesel, jet, and gasoline alternatives. Large scale production can be expensive and must be optimized to make algal biofuels commercially viable. When algae reaches maximum saturation, it is ready to be harvested, typically after a few weeks. In this research project a full factorial design is used to find optimal algae harvesting time (refer to Fig. 1).
2. Objectives
Find the optimal growth conditions for Nannochloris and Oocystis by adjusting salinity and sucrose levels for maximum lipid production.
Fixing the optimal growth parameters, continue to stress algae by depleting metals used during photosynthesis.
3. Results
Preliminary results (Figs. 2-4) show salinity does not have a statistical significant impact on the absorbance of the algae.
The pragmatic implication is that algae may be “stressed” in lower salt environments, which are less costly to algae farmers. Sucrose appears to drastically increase the absorbance of Oocystis algae and assists the algae in reaching steady state much sooner.
4. Conclusions
Salinity trials strained the algae to grow in “unnatural” environments. Nannochloris tests show lower salinity has no affect on the algae growth curve meaning facilities can lower operational costs with less precise salt content. Sucrose could be a promising investment for algae farms as it reduces the growth duration by roughly 20 days while nearly tripling the absorbance.
5. Future Work
A central composite design (CCD) in Fig. 1 will be run to obtain a response surface model. Next, the optimal solution obtained from the CCD will be stressed with metals such as copper, iron, nickel, zinc, manganese, and magnesium.
6. Acknowledgements
Financial assistance from the U.S. Department of Agriculture/National Institute of Food and Agriculture (Award Number: ) is gratefully acknowledged.
Salinity
Salinity
Sucrose
Sucrose
Fig. 1 Factorial and Central Composite Design
Fig. 2 Oocystis Absorbance- Sucrose
Fig. 4 Oocystis Absorbance- Salinity
Fig. 3 Nannochloris Absorbance - Salinity
Fig. 5 Algae Data Collection
Fig. 6 Algae on Shaker
Fig. 7 Dilution for Cell Count
Proceedings of the 2018 ASEE Gulf-Southwest Section Annual Conference The University of Texas at Austin
April 4-6, 2018