title: Growth kinetics and physiological behavior of co-cultures of Saccharomyces cerevisiae and Kluyveromyces lactis, fermenting carob sugars extracted with whey.
abstract: Alcoholic fermentation of carob waste sugars (sucrose, glucose and fructose) extracted with cheese whey, by co-cultures of Saccharomyces cerevisiae and Kluyveromyces lactis has been analyzed. Growth and fermentation of S. cerevisiae in the carob-whey medium showed an inhibition of about 30% in comparison with water-extracted carob. The inhibition of K. lactis on carob-whey was greater (70%) when compared with the whey medium alone, due to osmolarity problems. Oxygen availability was a very important factor for K. lactis, influencing its fermentation performance. When K. lactis was grown alone on carob-whey medium, lactose was always consumed first, and glucose and fructose were consumed afterwards, only at high aeration conditions. In co-culture with S. cerevisiae, K. lactis was completely inhibited and, at low aeration, died after 3 days; at high aeration this culture could survive but growth and lactose fermentation were only recovered after S. cerevisiae became stationary. To overcome the osmolarity and K. lactis' oxygen problems, the medium had to be diluted and a sequential fermentative process was designed in a STR-3l reactor. K. lactis was inoculated first and, with low aeration (0.13vvm), consumed all the lactose in 48h. Then S. cerevisiae was inoculated, consuming the total of the carob sugars, and producing ethanol in a fed-batch regime. The established co-culture with K. lactis increased S. cerevisiae ethanol tolerance. This fermentation process produced ethanol with good efficiency (80g/l final concentration and a conversion factor of 0.4g ethanol/g sugar), eliminating all the sugars of the mixed waste. These efficient fermentative results pointed to a new joint treatment of agro-industrial wastes which may be implemented successfully, with economic and environmental sustainability for a bioethanol industrial proposal.
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: B
authors.initials: B
authors.lastname: Rodrigues
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal. Electronic address: mcosta@ualg.pt.
authors.forename: M E
authors.initials: ME
authors.lastname: Lima-Costa
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Constantino
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: S
authors.initials: S
authors.lastname: Raposo
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: C
authors.initials: C
authors.lastname: Felizardo
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: D
authors.initials: D
authors.lastname: Gonçalves
authors.affiliation: Centre for Marine and Environmental Research (CIMA), Universidade do Algarve- Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Fernandes
authors.affiliation: Centre for Mediterranean Bioresources and Food (MeditBio), Universidade do Algarve-Campus de Gambelas, 8005-139, Faro, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Dionísio
authors.affiliation: Faculty of Biology, Department of Microbiology III, Universidad Complutense, 28040, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Peinado
mesh_terms: D050260:Carbohydrate Metabolism; D018920:Coculture Techniques; D003470:Culture Media; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005685:Galactans; D007700:Kinetics; D007716:Kluyveromyces / Q000254:growth & development* / Q000502:physiology*; D008351:Mannans; D053149:Plant Gums; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000502:physiology*; D000067796:Whey
chemical_list: D003470:Culture Media; D005685:Galactans; D008351:Mannans; D053149:Plant Gums; D000431:Ethanol; C017471:locust bean gum
keywords: Carob; Ethanol; Kluyveromyces lactis; Saccharomyces cerevisiae; Waste treatment; Whey