The yeast Kluyveromyces lactis can be seen as an alternative to the best known yeast Saccharomyces cerevisiae in biotechnological processes, with some advantages such as ability to assimilate higher number and kind of substrate and to yield higher biomass due its more oxidative metabolism. To better explore yeast in biotechnology it is important to understand its interaction with the environment. Yeast responds to substrate species through a complex transduction signal pathway which culminate in reprogramming its metabolism and growth rate. In this work different nitrogen sources such as ammonium sulfate, glutamine, glutamate or proline were evaluated for K. lactis according to the growth rate they allow, the metabolite they excrete and the extracellular protein synthesis they might induce. By SDS-PAGE of extracellular proteins, different eletrophoretic fractionation has been observed. While glutamate has resulted in higher number of bands with different molecular weight, glutamine has showed lower number of bands with molecular weight between 70 and 85 kDa. Amonium sulfate has allowed lower growth rate but higher extracellular protein concentration per biomass unit. Some of the metabolite excreted by the culture and observed by HPLC, such as glycerol and ethanol were analyzed according to the glucose consumption and carbon flow. Proline has yield higher ethanol compare to ammonium sulfate. Taken together those data can suggest the metabolic pathway and the physiological conditions for maximal biomass and extracellular protein yields.
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