Related Experiment Video
Updated: Mar 21, 2026
08:13
A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
Published on: December 25, 2015
17.9K
Redox potential driven aeration during very-high-gravity ethanol fermentation by using flocculating yeast.
Chen-Guang Liu1,2, Xue-Mi Hao2, Yen-Han Lin3
1School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
Scientific Reports
|May 11, 2016
Summary
Controlled aeration using redox potential (ORP) optimizes ethanol fermentation under very-high-gravity conditions. This method enhances yeast viability, flocculation, and separation, outperforming traditional aeration strategies.
Area of Science:
- Biotechnology
- Fermentation Science
- Yeast Physiology
Background:
- Ethanol fermentation requires oxygen for optimal yeast performance, particularly under very-high-gravity (VHG) conditions.
- Traditional dissolved oxygen (DO) sensors struggle to regulate aeration effectively at low DO levels in VHG fermentations.
- Oxidation-reduction potential (ORP) offers an alternative method for controlling aeration based on real-time oxygen demand.
Purpose of the Study:
- To investigate the efficacy of ORP-controlled aeration for ethanol fermentation under VHG conditions.
- To compare the performance of ORP-controlled aeration with constant aeration and no aeration strategies.
- To evaluate the impact of ORP-controlled aeration on yeast viability, biomass formation, glucose utilization, and ethanol production.
Main Methods:
- Flocculating yeast was cultured under VHG conditions (260-300 g glucose/L).
- Aeration strategies included no aeration, constant aeration (0.05 and 0.2 vvm), and ORP-controlled aeration (-150, -100, -50 mV).
- Fermentation performance metrics such as ethanol concentration, residual glucose, cell viability, and yeast flocculation were monitored.
Main Results:
- Anaerobic fermentation yielded the lowest ethanol and highest residual glucose.
- ORP-controlled aeration maintained higher cell viability compared to no aeration.
- Constant aeration led to rapid biomass and glucose consumption, but over-aeration (0.2 vvm) reduced final ethanol yield.
- ORP-controlled aeration demonstrated superior fermentation performance, enhanced yeast flocculating activity, increased floc size, and accelerated yeast separation.
Conclusions:
- ORP-controlled aeration is a superior strategy for managing aeration in VHG ethanol fermentation.
- This method optimizes yeast performance, leading to improved ethanol production and downstream processing benefits.
- ORP-based aeration control provides a viable alternative to DO sensors for low DO level regulation.
Related Concept Videos
01:18Bioreactor Controls-II
2
In aerobic fermentations, oxygen is vital for microbial growth and metabolite production. Since air comprises only about 20% oxygen and the gas is poorly soluble in water—just 9 ppm at 20°C—supplying sufficient oxygen becomes a critical challenge, especially in high-demand processes like yeast growth or citric acid production. Even a fully saturated broth may offer only a few seconds of oxygen availability.To address this, sterile or scrubbed air is introduced into the...
2
01:22Bioreactor Controls-III
21
Strain improvement is a foundational strategy in industrial microbiology aimed at maximizing microbial productivity, particularly because natural isolates typically yield commercially valuable products in very low concentrations. Although optimizing the culture medium and environmental conditions can improve yields, these adjustments are inherently limited by the organism’s genetic potential. As a result, the focus shifts toward genetic modifications to enhance biosynthetic capacity. The...
21
01:29Fermentation
132.7K
Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by metabolizing glucose and oxygen into carbon dioxide and water. However, most eukaryotes can generate some energy in the absence of oxygen by anaerobic metabolism.
Fermentation is a type of metabolic process that occurs in the absence of oxygen, where organic molecules such as glucose are broken down to produce energy. During this process, the...
Fermentation is a type of metabolic process that occurs in the absence of oxygen, where organic molecules such as glucose are broken down to produce energy. During this process, the...
132.7K
01:20Fates of Pyruvate
12.1K
Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also produced by substrate-level phosphorylation.
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
12.1K
01:23Microbial Fermentation
1.9K
Fermentation is a crucial anaerobic metabolic process that enables microbes to derive energy from sugar without relying on oxygen or an electron transport chain. This process is fundamental to various biological and industrial applications and is classified based on the metabolic products generated.Role of Pyruvate in FermentationPyruvate and its derivatives serve as key electron acceptors in fermentative pathways. The oxidation of NADH to regenerate NAD+ is essential for the continuation of...
1.9K
01:25Microbes in Beverage Production
16
Alcoholic beverages such as wine, beer, and spirits are the products of microbial fermentation processes that transform simple sugars into ethanol and a wide array of complex flavor compounds. These transformations rely on the metabolic activities of specific yeasts and bacteria, which are selected and controlled to yield the desired beverage characteristics.Wine Fermentation and MaturationWine production begins with the crushing of grapes to release juice and pulp, forming a must that is...
16