[Optimizing conditions for the discontinuous production of unicellular protein using whey]

The cheese whey is one of the most important effluents which is being disposed off in our area. That is why the study for optimizing conditions in the process of recovering whey to produce protein biomass in a batch fermenter was undertaken. A yeast strain (Kluyveromyces marxianus var. lactis) was propagated on a medium based on whey from cheese making plants, the following conditions for cell development being optimized: temperature, pH and initial concentration of lactose. A methodology based on performing several tests ordered according to a "Latin Squares" structure was proposed; this enables the simultaneous study of three variables with a small number of experiences. Such experiences were performed in a cylindrical (air lift type) glass fermenter, obtaining a maximum yield (4.78 g/l by dry weight) when working with an initial lactose concentration equal to 4.8%. For all temperatures (27, 30 and 35 degrees C) and pH (3, 4 and 5) employed, an increase in the cell number occurred with the initial lactose concentration increasing from 2% to 4.8% (Table 2). It is preferable to work at 27 degrees C and pH 4 (since these conditions minimize the bacterial contamination) and with a lactose concentration equal to 4.8%, i.e. the concentration in the residual cheese whey. Thus, an optimum yield in protein biomass is obtained, enabling a good utilization of this effluent, and also diminishing its initial BOD from 60,000 to 15,000 ppm.