High-rate ethanol production at low pH using the anaerobic granular sludge process

Jelmer Tamis*, Bart Joosse, Kasper de Leeuw, Robbert Kleerebezem

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)


In this study, we investigated the operational performance and product spectrum of glucose-fermenting anaerobic granular sludge reactor at pH 4. A selective environment for the growth of granules was implemented by the introduction of a 2 min settling phase, a hydraulic retention time of 6 h and a solid retention time of 12 ± 3 days. The fermentation products were ethanol, lactate, and volatile fatty acids (VFA) with yields of 0.55 ± 0.03, 0.15 ± 0.02, and 0.20 ± 0.04 gram chemical oxygen demand (gCOD)/gCOD glucose, respectively. The obtained product spectrum was remarkably different from the VFA-dominated product spectrum reported in a previous study when the same system was operated at higher pH (4.5–5.5). The shift in product spectrum coincided with a shift in the microbial community structure with the dominance of eukaryotic Candida tropicalis, Pichia jaroonii, and prokaryotic Lactobacillus species instead of the Clostridia species obtained at higher pH-values. The control of the microbiomes and the associated product spectra provides bioprocess engineers with the option to tailor a suitable precursor compound mixture for subsequent chain elongation fermentation or PHA biopolymer production.

Original languageEnglish
Pages (from-to)1943-1950
Number of pages8
JournalBiotechnology and Bioengineering
Issue number5
Early online date6 Feb 2021
Publication statusPublished - 2021


  • ethanol
  • granular sludge
  • open/mixed culture fermentation
  • resource recovery
  • VFA


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