1:00 pm - 2:00 pm
130 Agriculture/Forestry Centre, University of Alberta, Edmonton
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree. This is an ALES MSc Final Exam Seminar by Haley Wolgien-Lowe. This seminar is open to the general public to attend.
Google Meet: https://meet.google.com/ezm-dsrj-bbt
MSc with Dr. David Bressler
Thesis Topic: From Fermenter to Farm: Downstream Processing of Single Cell Protein
Abstract:
The global demand for meat is rapidly increasing, causing extensive overfishing and deforestation to provide livestock with high value feed and protein supplements. Alternative protein sources have been sought to reduce the environmental impact of these activities and redirect crop and food production toward humans. One such product is single cell protein, which is comprised of unicellular microorganisms that are high in protein. These products are produced through fermentation and reduce water, land, and nutrient requirements compared to conventional protein sources such as soymeal. In this work, single cell protein produced through methanol fermentation of Methylophilus methylotrophus AS1 was processed by different separation and drying methods to determine their efficacy and effect on the quality of the final product.
Proximate analysis of Methylophilus methylotrophus AS1 biomass determined its composition of 79% amino acids, 16% lipids, and 4.7% ash. Microbial cells were visualized by scanning electron microscopy and the average cell length of 1200 ± 200 nm and width of 300 ± 30 nm were determined for the first time. It was found that increasing substrate feed rate increased the cell width but not length, and stressful growth conditions caused cell lysis and formation of a white debris layer. Additionally, prolonged storage caused deformation, lysis, and clumping of the cells.
Flocculation and cross-flow membrane filtration separation methods were investigated and compared to centrifugation as a reference method. Flocculation was induced by heating at 70 °C and acidification to pH 3, and cross-flow filtration utilized a 0.2 μm PVDF flat sheet microfiltration membrane. The highest biomass recovery was achieved through flocculation, which also concentrated the material to a greater extent than cross-flow filtration. However, cross-flow filtration was more selective in separating the cells from the spent media. Overall, both methods produced a final product comparable to centrifugation, and product quality was maintained.
Spray drying was utilized as a test method against freeze drying as a control. Spray drying at 200 °C inactivated originally viable cells and produced a fine, light, free-flowing, homogenous powder with moisture contents between 4.3-7.4%. Most importantly, the product composition and amino acid content of the spray dried material was retained.
Overall, it was determined that single cell protein from Methylophilus methylotrophus AS1 was resistant to protein degradation and compositional changes from exposure to heat, acidification, and shear stress induced by the separation and drying methods tested. The results of this work support further development of downstream processing methods and enable greater freedom in selection of separation methods for industrial applications. Due to the stability and robustness of the product through the separation and drying methods tested, process development activities may focus on other parameters such as efficiency, energy requirements, environmental impact, and safety. Additionally, the high amino acid content indicates Methylophilus methylotrophus AS1 is an excellent organism to produce single cell protein for animal feed.
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