title: Maximizing hydrogen production and substrate consumption by Escherichia coli WDHL in cheese whey fermentation.
abstract: Fermentative hydrogen production is strongly affected by pH. In order to maximize hydrogen production and substrate consumption in Escherichia coli ΔhycA, ΔlacI (WDHL) cheese whey fermentation, the influence of pH control at values of 5.5, 6, and 6.5 was studied in batch stirred-tank bioreactors. From the conditions evaluated, pH 6.5 was the best condition, at which the highest cumulative hydrogen production and yield (1.78 mol H2/mol lactose) were obtained. Moreover, at this pH, all carbohydrates from the cheese whey were consumed, and a mix of ethanol and organic acids, mainly lactate, were produced from glucose, whereas galactose yielded acetate, ethanol, and succinate. Operating the reactor at pH 5.5 resulted in the highest maximum specific production rate, but smaller hydrogen yield because only glucose was metabolized and galactose was accumulated. At pH 6, not all cheese whey carbohydrates were consumed, and it was not favorable for hydrogen production. Lactose consumption and growth kinetics were not affected by the pH. The results show the importance of controlling pH to maximize hydrogen production and substrate consumption using cheese whey as substrate.
authors.affiliation: División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Col. Lomas 4ª secc, CP 78216, San Luis Potosí, San Luis Potosí, Mexico, rosalesphd@gmail.com.
authors.forename: Luis Manuel
authors.initials: LM
authors.lastname: Rosales-Colunga
authors.forename: Zazil Donaxí
authors.initials: ZD
authors.lastname: Alvarado-Cuevas
authors.forename: Elías
authors.initials: E
authors.lastname: Razo-Flores
authors.forename: Antonio De León
authors.initials: Ade L
authors.lastname: Rodríguez
mesh_terms: D019149:Bioreactors; D002611:Cheese; D043302:Cultured Milk Products / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007785:Lactose / Q000378:metabolism*
chemical_list: D006859:Hydrogen; D007785:Lactose