ORIGINAL PAPER Effects of Urea Supplementation on Candida utilis Biomass Production from Distillery Waste Roxana Garcı ´a • Yaima Izquierdo • Mauricio Ribas • Keyla Tortolo ´ • My-lai Iba ´n ˜ez • Olga Leo ´n • Maribel Saura • Gustavo Saura Received: 16 November 2012 / Accepted: 5 February 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract 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 sul- phate 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 % phos- phorous) were affected with regard to the use of ammo- nium 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 for- mulation of the culture medium in order to maintain opti- mum pH for the propagation of the yeast and in order to counteract bacterial contamination. Keywords Ammonium  Candida utilis  Distillery waste  Fodder yeast  Nitrogen  Urea Introduction The technology for single cell protein (SCP) production from distillery slop or vinasse as carbon and energy source constitutes an economically feasible process whose great- est impact has been the reduction of the pollution load in this, the main wastewater generated by the industry of sugar cane byproducts [1]. The efficiency of this process depends on the characteristics of the vinasse, the contri- bution of macro-elements sources, growth factors as well as physicochemical parameters such as temperature and pH. Fodder yeast Candida utilis commonly called Torula yeast, is the industrial microorganism more used in Cuba for the production of SCP as an established product with R. Garcı ´a (&) Biotechnology Division, Microbiology Department, Cuban Research Institute of Sugar Cane Byproducts (ICIDCA), Vı ´a Blanca No. 804 y Carretera Central, San Miguel del Padro ´n, AP. 4026, CP 11000 La Habana, Cuba e-mail: roxana.garcia@icidca.edu.cu Y. Izquierdo Chemistry Division, ICIDCA, La Habana, Cuba M. Ribas Development Division, ICIDCA, La Habana, Cuba K. Tortolo ´  M. Iba ´n ˜ez  O. Leo ´n  M. Saura  G. Saura Biotechnology Division, ICIDCA, La Habana, Cuba 123 Waste Biomass Valor DOI 10.1007/s12649-013-9209-z