ABSTRACT
Since the late twentieth and early 20-first century, the needs of a competitive pharmaceutical and food industry have contributed to the growth of the discipline of biotechnology. This growth has been particularly important in molecular biology and genetic engineering, which has been favored by the great market potential of these technologies in the development of new drugs, and the farming industry. Traditionally, organisms were chosen and used for their ability to produce a compound of interest. Currently, the techniques of genetic engineering allow us to use an organism whose physiology is suitable for use in the laboratory and in the synthesis of recombinant proteins, which in its wild (natural) state, would not. There are a variety of organisms employed for this purpose, having used bacteria such as Escherichia coli, filamentous fungi such as Aspergillus niger, higher plants such as Arabidopsis thaliana and higher mammals such as the cow (Bos taurus). However, the object of analysis in this chapter is to review the focus of the yeast organisms as producers of recombinant proteins, specifically we refer to the methylotrophic yeasts. The yeasts are suitable for this type of procedure for several reasons, for example, the physiology of growth is similar to the bacterial. Additionally, it refers to the processes of manipulation of genetic material, which are also very similar to the techniques used with bacteria, which in turn makes it easy to use in laboratory conditions. Other desirable characteristics of these organisms are that, unlike bacteria, they possess mechanisms to synthesize eukaryotic proteins, such as posttranscriptional modifications, proteolytic processing, protein folding mechanisms and glycozylation (Eckart, 1996). In addition, yeast cultures have high yields of biomass and in terms of money and effort costs are low (Creeg, 1999). Finally, another interesting feature of these microorganisms is that it has been found that yeast is free of endotoxins, an advantage for its applications in pharmaceuticals and agriculture (Glick and Pasternak, 1998). However, the yeasts also have some disadvantages, the most relevant are related to some complex procedures such as transcriptional modification, polyhydroxylation and amidation, as well as mechanisms of phosphorylation (Creeg, 1995). Although some studies indicate that these disadvantages can be corrected, which ensure the use of these organisms.
