?Growth dynamics and metabolites produced in the fermentation of Candida norvegensis yeast

Abstract

An experiment was conducted to know the growth dynamics and metabolites produced by a yeast strain with potentialities as activator of the ruminal fermentation. The strain belongs to Candida norvegensis and is called Levazoot 15. A completely randomized design, with four repetitions in each study hour, was applied. The variables optic density, biomass, brix degrees, lactic acid and ammoniac nitrogen were determined. The results show that the performance of the optic density and that of the biomass were similar in time. The higher values were reached at 36 h (1.75 and 0.024, respectively). Consequently, the brix degrees diminished from 1.65 at 0 h, up to 0.73 in the 36 h. The levels of ammoniac nitrogen were reduced from 0.70 mM to 0.32 mM in the 12 h. The pH diminished up to the 12 h, but increased slightly from 16 h on. Similar performance was observed in the concentration of lactic acid, diminishing from 3.26 ?g to 1.196 ?g, for increasing later from 3.244 ?g to 36 h. It is concluded that the Levazoot 15 (Candida norvegensis) strain showed its maximum growth at 16 h, with pH of 4.17 under the conditions of this study. This is the proper time to use the yeast culture and prove its effect as ruminal activator.
Key words: yeast, dynamic, growth, Candida norvegensis.