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Dissertation/Thesis Abstract

Microbial Cell Disruption Using Pressurized Gases to Improve Lipid Recovery from Wet Biomass: Thermodynamic Analysis
by Howlader, Md Shamim, Ph.D., Mississippi State University, 2018, 244; 10790070
Abstract (Summary)

Microbial cell disruption using pressurized gas is a promising approach to improve the lipid extraction yield directly from the wet biomass by eliminating the energy-intensive drying process, which is an integral part of traditional methods. As the process starts with the solubilization of the gas in lipid-rich microbial cells, it is important to understand the solubility of different potential gases in both lipid (triglyceride) and lipid-rich microbial cell culture to design efficient cell disruption processes. In this study, we determined the solubility of different gases (e.g., CO2, CH4, N 2, and Ar) in canola oil (triglyceride) using a pressure drop gas apparatus developed in our laboratory. The solubility of different gases in triglyceride followed the trend CO2 > CH4 > Ar > N2. Since the solubility of CO2 was found to be higher compared to other gases, the solubility of CO2 in lipid rich cell culture, cell culture media, and spent media was also determined. It was found that CO2 is more soluble in triglycerides, but less soluble in lipid-rich cell culture compared to CO2 in water. From both thermodynamic models and Monte Carlo simulations, the correlated solubility was found to be in good agreement with the experimental results. CO2 was found to be the most suitable gas for microbial cell disruption because almost 100% cell death occurred when using CO2 whereas more than 85% cells were found to be active after treatment with CH4, N2, and Ar. The optimization of microbial cell disruption was conducted using the combination of Box-Behnken design of experiment (DOE) technique and response surface methodology. The optimized cell disruption conditions were found to be 3900 kPa, 296.5 K, 360 min, and 325 rpm where almost 100% cell death was predicted from the statistical modeling. Finally, it was found that 86% of the total lipid content can be recovered from the wet biomass after treatment with pressurized CO2 under optimized conditions compared to control where up to 74% of the total lipid content can be recovered resulting in 12% increase in the lipid extraction yield using pressurized CO2.

Indexing (document details)
Advisor: French, William T., Rai, Neeraj
Commitee: DuBien, Janice, Pearson, Larry, Toghiani, Hossein
School: Mississippi State University
Department: Chemical Engineering
School Location: United States -- Mississippi
Source: DAI-B 79/09(E), Dissertation Abstracts International
Subjects: Chemical engineering
Keywords: Biofuels, Lipid extraction, Oleaginous microorganisms, Optimization, Solubility, Thermodynamic models
Publication Number: 10790070
ISBN: 978-0-355-92200-4
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