| Microorganisms are a promising lipid producer of polyunsaturated fatty acid (PUFA) rich oils that have numerous therapeutic benefits. The fungi Pythium irregulare is capable of producing intracellular oil containing the PUFAs o-3 eicosapentaenoic (EPA) and o-6 arachidonic (ARA). Submerged cultures studies investigating oil production over a broad temperature range (14, 21, and 28°C) found maximum oil production, 0.893 mg/ml, occurring at 21°C and 4 days of fermentation.; Oil extraction methods originally designed for animal tissue and plant material can degrade the fragile PUFA-rich oil. Supercritical fluid extraction (SFE) using CO2 (Tc = 31.1°C, Pc = 7.38 MPa) can be used to deter PUFA destruction. Mathematical models can describe the extraction process during the early phases; however, once diffusion-controlled regimes are approached, the models overestimate oil yield when applied to the CO2-P. irregulare system (T = 40°C, P = 20.7MPa).; Intact cells contribute to the diffusion-controlled regime since the intracellular oil must travel through the cell walls to the surface for extraction. Thus, the overall oil extraction is not as high as it could be; cellular disruption would enhance the overall oil extraction by exposing more surface oil to the CO2 solvent. One novel approach for enhancing CO2-SFE of fungal lipids is through the application of a CO2-explosion pretreatment where the fungal biomass is ruptured by the rapid change of CO 2 from a supercritical to atmospheric gaseous state.; A lab-scale apparatus integrating the bioprocessing techniques of CO 2-explosion with SFE was constructed and used to investigate the ability of CO2-explosion to enhance the extraction of a PUFA-rich oil from P. irregulare biomass. The soaking time was varied at 20 or 60 minutes along with the soaking pressure (27.6 and 10.3 MPa). The temperature remained constant at 40°C. All explosion pretreatments increased SFE oil yield after 90 minutes when compared to non-explosion-treated biomass; the greatest increase was noted for the (10.3 MPa, 60-min) pretreatment with a 25% increase from 0.593 to 0.743 g oil/g total oil. With respect to target PUFAs, explosion pretreatment increased the EPA and ARA concentrations in the extracted oil, nearly doubling their weights and suggesting promising applications. |
