title: New generation biofuel: continuous acidogenesis of sucrose-raffinose mixture simulating vinasse is promoted by γ-alumina pellets.
abstract: BACKGROUND
  This investigation comprises a contribution on the production of a new generation biofuel using the industrial liquid waste of bioethanol distilleries, known as vinasse. This study focuses on the exploitation of vinasse as an acidogenesis substrate for volatile fatty acids and simultaneous ethanol production. These products can be used for ester production, which is the new generation biofuel. Therefore, the aims of the present study are (i) to examine any promotional effect of γ-alumina on acidogenesis of a sucrose-raffinose mixture simulating vinasse, (ii) to study the operational stability of the continuous acidogenesis of sucrose and raffinose and subsequently of vinasse, and (iii) to determine the volatile fatty acid chemical composition and ethanol formation.
  
  
  RESULTS
  Batch acidogenesis of sucrose and raffinose mixtures showed that γ-alumina promoted fermentation leading to an increase in the volatile fatty acid yield factor from 40% to 95% compared to free cells. The application of the system in continuous mode for more than 3 months showed that the continuous volatile fatty acid productivity obtained was higher than 7 g/L/day. Lactic acid was the predominant acid when sucrose and raffinose were used while butyric acid in the case of vinasse. The highest volatile fatty acid concentration reached was 19 g/L for vinasse.
  
  
  CONCLUSIONS
  A promoting effect of γ-alumina in acidogenic fermentation of sucrose-raffinose and vinasse is reported. Continuous acidogenesis of sucrose-raffinose mixtures and vinasse using γ-alumina with immobilized cells showed high operational stability (more than 3 months). These findings result in easy scale up of the process that will produce a high annual added value of $11,000,000 in a daily bioethanol production plant of 50,000 L.
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, 26500 Patra, Greece.
authors.forename: Katerina
authors.initials: K
authors.lastname: Lappa
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, 26500 Patra, Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kandylis
authors.affiliation: B.G. Spiliopoulos S.A, 26500 Patra, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Bastas
authors.affiliation: B.G. Spiliopoulos S.A, 26500 Patra, Greece.
authors.forename: Stavros
authors.initials: S
authors.lastname: Klaoudatos
authors.affiliation: I. Athanasopoulos and Co, 106b Lontou Str, 26224 Patra, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Athanasopoulos
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, 26500 Patra, Greece.
authors.forename: Argyro
authors.initials: A
authors.lastname: Bekatorou
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, 26500 Patra, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Kanellaki
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, 26500 Patra, Greece.
authors.forename: Athanasios A
authors.initials: AA
authors.lastname: Koutinas
keywords: Acidogenic fermentation; Butyric acid; Ethanol; Lactic acid; Raffinose; Vinasse; Volatile fatty acids; γ-Alumina