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Havana, Cuba

Garcia R.,Cuban Research Institute of Sugar Cane Byproducts ICIDCA | Izquierdo Y.,ICIDCA | Ribas M.,ICIDCA | Tortolo K.,ICIDCA | And 4 more authors.
Waste and Biomass Valorization

Purpose In the industrial process of propagation of fodder yeast from distillery waste, a proper balance of nitrogen salts available commercially is crucial. This paper describes a study to determine the effect of replacing ammonium sulphate with urea in the propagation of Candida utilis from the distilled residual derived from alcoholic fermentation of filter mud juice. A reformulation in the growth medium may offer an alternative nitrogen source without affecting quality parameters of the final product. Methods A characterization of major raw materials and a Simplex-Lattice experimental design considering nitrogen salts mixtures were performed to determine the best variant. Results Candida utilis, L/3-75-7 responded favorably at a laboratory scale in the presence of urea with average values of 9.80 g l-1, 80.03 and 53.76 % of net biomass, substrate conversion efficiency and percent removal of chemical oxygen demand, respectively. There was a significant impact on the increase of pH by using urea, with final values in the neutral zone. None of the quality parameters evaluated for yeast (net protein 43.87 and 2.19 % phosphorous) were affected with regard to the use of ammonium sulphate. Conclusions From the equations obtained for models that define the behavior of the percentage of removal of chemical oxygen demand, conversion efficiency and final pH adjustment, these parameters could be predicted by replacing the nitrogen added via ammonium with urea according to availability. Special attention should be paid to pH levels when urea additions are increased in the formulation of the culture medium in order to maintain optimum pH for the propagation of the yeast and in order to counteract bacterial contamination. © Springer Science+Business Media Dordrecht 2013. Source

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