PhD candidates: Susana Pedraza de la Cuesta, Rita da Costa Basto and Meissa Essenfelder Abrahao
Hydrophobic compounds (lipids, alkanes, isoprenoids) produced by microorganisms have a huge potential for use as transport fuel and platform chemicals. While many naturally occurring micro-organisms have the ability to accumulate lipids (mostly as triacylglycerol) intracellularly, the last decade has seen rapid advances in the extracellular production of tailored hydrophobic products using engineered micro-organisms (mostly E. coli and S. cerevisiae). The main features of this route are: a) the extracellular production, making cell retention possible and facilitating product recovery in a separate organic phase; and b) the possibility of tailoring the type of product obtained. However, the turbulent conditions of a bioreactor, and the presence of a breadth of surface active components in the fermentation broth, result in the stabilisation of the product droplets. As a consequence, product recovery is hindered and requires intensive centrifugation and the use of (costly) chemical demulsifiers. In other words, the potential economic benefits of a phase-separating product are currently being missed! Hence, this project aims at developing a bioreactor with integrated oil product recovery and cell recycle, and its demonstration at pilot scale.
PhD candidate: Joan Sebastián Gallego Murillo
Transfusion of red blood cells (RBCs) is the most commonly used form of cell therapy. Currently, blood donations are the only source of RBCs for transfusion purposes. This system has several problems that put at risk the availability of RBCs: increase demand in the future due to population aging, allo-immunization, inability to detect emerging diseases in donated blood, and shortage of donations, especially in developing countries. An alternative to this is the in vitro production of RBCs.
In the human body production of RBCs is a process known as erythropoiesis, in which multipotent cells follow a differentiation and maturation progression. In vitro manufacture of RBCs follows the same general process that happens in the body, in which two main stages can be identified: expansion of nucleated cells with self-renewal abilities (mainly erythroblasts), and differentiation of these cells into RBCs. In vitro expansion of erythroblasts and their differentiation into RBCs has been achieved, and it is usually performed under static cultivation conditions, in culture dishes or small (<200 mL) flasks.
Scaling-up of this static process presents challenges due to lack of knowledge on the tolerance of erythroblasts to the conditions of a bioreactor. Also, a limitation in maximum cell density have been observed in preliminary experiments and must be overcome to develop an economically feasible cultivation process. This project is focused on these problems and has as main goal the design of a bioreactor system that allows the expansion of erythroblasts and their differentiation into RBCs for transfusion purposes. Questions such as under which shear stress conditions erythroblast can divide, which bioreactor concepts are compatible with the growth of these cells, what is the most appropriate feeding strategy for this system, and how to reduce the cost of the growth media are going to be addressed.
Project partner: Sanquin Research, Department of Hematopoiesis