title: Effect of fermentation conditions on the flocculation of recombinant Saccharomyces cerevisiae capable of co-fermenting glucose and xylose.
abstract: Flocculation is a desirable property in industrial yeasts and is particularly important in the fuel ethanol industry because it provides a simple and cost-free way to separate yeast cells from fermentation products. In the present study, the effect of pH and lignocellulose-derived sugars on yeast flocculation was investigated using a flocculent Saccharomyces cerevisiae, MA-R4, which has been recombinantly engineered to simultaneously co-ferment glucose and xylose to ethanol with high productivity. The flocculation level of MA-R4 dramatically decreased at pH values below 3.0 during co-fermentation of glucose and xylose. Sedimentation and microscopic observation revealed that flocculation was induced in MA-R4 when it fermented glucose, a glucose/xylose mixture, or mannose, whereas attempts to ferment xylose, galactose, and arabinose led to the loss of flocculation. MA-R4 fermented xylose and galactose more slowly than glucose and mannose. Therefore, the various flocculation behaviors shown by MA-R4 should be useful in the control of ethanol fermentation processes.
authors.affiliation: Biomass Refinery Research Center (BRRC), National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046, Japan, a-matsushika@aist.go.jp.
authors.forename: Akinori
authors.initials: A
authors.lastname: Matsushika
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Morikawa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Goshima
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Hoshino
mesh_terms: D005285:Fermentation; D005427:Flocculation; D005947:Glucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D014994:Xylose; D005947:Glucose