Engineered S. cerevisiae

Tsai et al. [84]. Ongoing development in the industrialization of xylose-fermenting yeast has been reviewed in [16]. 

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The rHBsAg is produced in an engineered S. cerevisiae strain and is likely purified subsequent to fermentation by a procedure somewhat similar to that presented in Figure 13.10. The final product is presented as a sterile suspension of the antigen absorbed onto aluminium hydroxide (adjuvant), in either single-use vials or pre-filled syringes. It also contains NaCl and phosphate buffer components as excipients. It is intended for i.m. injection, usually as 10 pg in a volume of 0.5 ml for infants/children or 20 pg (in 1.0 ml) for adults. The normal dosage schedule entails initial administration followed by boosters after 1 and 6 months. 

Autologous bone marrow transplantation involves initial removal of some marrow from the patient, its storage in liquid nitrogen, followed by its re-introduction into the patient subsequent to chemo- or radiotherapy. Leukine is the tradename given to a recombinant human GM-CSF preparation produced in engineered S. cerevisiae (Table 6.4). 

With the development of metabolic engineering the role of S. cerevisiae as cell factory became further consolidated. Numerous approaches to engineer S. cerevisiae for the production of a wide range of chemicals can be found in the literature. Whereas the most promising are summarized in Table 6, we will describe below just a few examples where metabolic engineering of yeast has been applied in industrial biotechnology. 

Another example of chemicals produced with help of metabolic engineering are sterols. The most well-known sterol is cholesterol. Sterols are important for living organisms as they are a part of the cellular membrane, participate in the synthesis of several hormones, and are also nutrient supplements. Several sterols are being produced from metabolically engineered S. cerevisiae. 

S. cerevisiae strain produced 13 g 1 of SA with a yield of 0.21 mol mol glucose in a medium supplemented with CaCOg, urea, and biotin at pH 3.8 [91]. Table 17.7 summarizes the performance of the engineered S. cerevisiae strains. 

More recently, the substrate range of S. cerevisiae has been expanded to include cellulose [50]. This project included the unusual approach of designing a consortium of four engineered S. cerevisiae strains in which each of the four strains expresses and secretes a different component of the cellulose-degrading cellul-some complex. When grown together, these four strains were able to produce 1.2 gl" ethanol while consuming cellulose [50]. 

Similarly, reductions of different racemic 2-oxabicyclo[3.2.0]heptan-6-ones [139], 2-oxabicyclo[2.2.1]heptane-7-carboxylates [140], norbomenone [102], and bicyclo[2.2.2]octan-2-one [141] have been performed the ee values, however, were moderate. For the reduction [141] of a 4-twistanone (tricyclo[4.4.0.0 ]decan-4-one), the alternative use of Rhodotorula rubra has been suggested. Kinetic resolution of racemic 5,6-epoxy-bicyclo[2.2.1]heptane-2-one using whole cells of genetically engineered S. cerevisiae allowed the synthesis of (+)-5,6-epoxy-bicyclo[2.2.1] heptane-2-ol [142]. 

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