title: A modified indirect mathematical model for evaluation of ethanol production efficiency in industrial-scale continuous fermentation processes.
abstract: OBJECTIVE
  To calculate fermentation efficiency in a continuous ethanol production process, we aimed to develop a robust mathematical method based on the analysis of metabolic by-product formation.
  
  
  RESULTS
  This method is in contrast to the traditional way of calculating ethanol fermentation efficiency, where the ratio between the ethanol produced and the sugar consumed is expressed as a percentage of the theoretical conversion yield. Comparison between the two methods, at industrial scale and in sensitivity studies, showed that the indirect method was more robust and gave slightly higher fermentation efficiency values, although fermentation efficiency of the industrial process was found to be low (~75%).
  
  
  CONCLUSIONS
  The traditional calculation method is simpler than the indirect method as it only requires a few chemical determinations in samples collected. However, a minor error in any measured parameter will have an important impact on the calculated efficiency. In contrast, the indirect method of calculation requires a greater number of determinations but is much more robust since an error in any parameter will only have a minor effect on the fermentation efficiency value.
  
  
  CONCLUSIONS
  The application of the indirect calculation methodology in order to evaluate the real situation of the process and to reach an optimum fermentation yield for an industrial-scale ethanol production is recommended. Once a high fermentation yield has been reached the traditional method should be used to maintain the control of the process. Upon detection of lower yields in an optimized process the indirect method should be employed as it permits a more accurate diagnosis of causes of yield losses in order to correct the problem rapidly. The low fermentation efficiency obtained in this study shows an urgent need for industrial process optimization where the indirect calculation methodology will be an important tool to determine process losses.
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: M A
authors.initials: MA
authors.lastname: Canseco Grellet
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Castagnaro
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: K I
authors.initials: KI
authors.lastname: Dantur
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: G
authors.initials: G
authors.lastname: De Boeck
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: P M
authors.initials: PM
authors.lastname: Ahmed
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: G J
authors.initials: GJ
authors.lastname: Cárdenas
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina.
authors.forename: B
authors.initials: B
authors.lastname: Welin
authors.affiliation: Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITANOA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Estación Experimental Agroindustrial Obispo Colombres (EEAOC), Las Talitas, Tucumán, Argentina. programabioenergia@hotmail.com.
authors.forename: R M
authors.initials: RM
authors.lastname: Ruiz
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000378:metabolism*; D000431:Ethanol / Q000032:analysis / Q000378:metabolism*; D005285:Fermentation; D007218:Industrial Microbiology / Q000379:methods*; D008962:Models, Theoretical
chemical_list: D000431:Ethanol
keywords: bioethanol; continuous fermentation process; fermentation efficiency; indirect calculation method; mathematical model