innovative consecutive batch fermentation process for very high gravity ethanol fermentation with self-flocculating yeast

• Published in: Applied microbiology and biotechnology Vol. 84; no. 6; pp. 1079 - 1086
• Main Authors: Li, F, Zhao, X. Q, Ge, X. M, Bai, F. W
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.10.2009; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Bioengineering; Biological and medical sciences; Biomass; Biomass energy; Biotechnological Products and Process Engineering; Biotechnology; Cooling; Energy consumption; Ethanol; Ethanol - metabolism; Fermentation; Flocculation; Fundamental and applied biological sciences. Psychology; Glucose; Industrial Microbiology - economics; Industrial Microbiology - methods; Life Sciences; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Microbial Genetics and Genomics; Microbiology; Process engineering; Sedimentation & deposition; Studies; Yeast; Yeasts - chemistry; Yeasts - growth & development; Yeasts - metabolism; VHG; Self-flocculating yeast; Consecutive ethanol fermentation; Yeast; Batchwise; Ethanol; Flocculation; Fermentation; Operating process
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-009-2043-3

An innovative consecutive batch fermentation process was developed for very high gravity (VHG) ethanol fermentation with the self-flocculating yeast under high biomass concentration conditions. On the one hand, the high biomass concentration significantly shortened the time required to complete the VHG fermentation and the duration of yeast cells suffering from strong ethanol inhibition, preventing them from losing viability and making them suitable for being repeatedly used in the process. On the other hand, the separation of yeast cells from the fermentation broth by sedimentation instead of centrifugation, making the process economically more competitive. The VHG medium composed of 255 g L⁻¹ glucose and 6.75 g L⁻¹ each of yeast extract and peptone was fed into the fermentation system for nine consecutive batch fermentations, which were completed within 8-14 h with an average ethanol concentration of 15% (v/v) and ethanol yield of 0.464, 90.8% of its theoretical value of 0.511. The average ethanol productivity that was calculated with the inclusion of the downstream time for the yeast flocs to settle from the fermentation broth and the supernatant to be removed from the fermentation system was 8.2 g L⁻¹ h⁻¹, much higher than those previously reported for VHG ethanol fermentation and regular ethanol fermentation with ethanol concentration around 12% (v/v) as well.