| الوصف: |
Glycosphingolipids (GSLs), constituted by a glycan moiety and a ceramide tail, play crucial roles in the development, regulation, and maintenance of cell functions. Phytosphingosine is a sphingoid base that is part of the GSLs ceramide and can be produced through fermentation by the yeast Wickerhamomyces ciferrii, that naturally secretes acetylated phytosphingosines. The expensive carbon source, pure glycerol, used in these fermentations can be replaced by an economic alternative, such as crude glycerol from the biodiesel industry, although it may contain impurities that negatively affect fermentation. W. ciferrii requires nutrient-rich concentrated media, that can lead to saturation and formation of undesired precipitates, like struvite, an orthophosphate mineral formed by the ions Mg²⁺, NH₄⁺ and PO₄³⁺, which may negatively affect fermentation. This internship was developed at CarboCode, a company whose core activity is the production of GSLs to apply in cosmetics, food, and pharmaceutical markets. This project aimed to optimize the standard CarboCode fermentation, that uses the yeast W. ciferrii, by avoiding struvite precipitation in the fermentation, and by replacing the carbon source, pure glycerol, to reduce costs. To avoid struvite, precipitations tests were performed, followed by shake flask fermentations assays, where the addition of sodium hexametaphosphate (SHMP) to CarboCode medium proved to be the most promising solution, as it successfully chelates with Mg²⁺, preventing struvite formation. A more efficient fermentation was promoted, as xxx g L⁻¹ of product were achieved, result that outperformed the standard assay with xxx g L⁻¹. In a bioreactor, the pH reduction of the standard assay was evaluated, which also allowed to avoid struvite precipitation, however considering the standard assay where xxx g L⁻¹ of product were attained, there was no improvement in the results. To reduce the carbon source cost, crude glycerol samples from Biodiesel companies were tested, from which the most promising one ... |
