Yeast Propagation via Two-Phase Feeding to Overcome Crabtree Inhibition
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Solution Overview
Problem
Current ethanol production processes face challenges in efficiently propagating genetically modified yeasts and other microorganisms that suffer from growth inhibition by the feeding medium, particularly due to the Crabtree effect, leading to high costs and reduced productivity.
Innovation Solution
A fed-batch propagation strategy involving at least two exponential feeding phases without feedback control is employed, using low-cost streams from ethanol production plants, such as diluted lignocellulosic hydrolysate streams, to optimize sugar use and accelerate fermentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional single-phase batch propagation is used, then process simplicity is maintained, but cell expansion is limited and propagation time increases
Solution Approach 1:
The propagation process is divided into two distinct exponential feeding phases: Phase 1 with higher growth rate (μ1) for rapid cell expansion, and Phase 2 with lower growth rate (μ2) for optimized biomass production. This segmentation allows each phase to be optimized for its specific function, achieving over 100-fold cell expansion while maintaining process control through defined feeding strategies rather than complex feedback systems.
2Speed
If high inocula concentrations are used to accelerate fermentation, then fermentation speed increases, but propagation costs and time increase
Solution Approach 1:
The two-phase exponential feeding strategy performs preliminary cell expansion work during the propagation phase, building up high cell density inoculum (over 100-fold expansion) before fermentation begins. This preliminary action ensures that sufficient viable cells are available at the start of fermentation, enabling rapid fermentation without requiring excessively long propagation times or incurring high propagation costs.
3Productivity
If feeding medium concentration is increased to support rapid growth, then cell growth rate improves, but Crabtree effect inhibition increases
Solution Approach 1:
The feeding strategy dynamically adjusts substrate concentration through two distinct exponential feeding phases. Phase 1 uses a feeding rate optimized for rapid growth with higher substrate availability, while Phase 2 transitions to a lower feeding rate that maintains sufficient growth while reducing substrate concentration to minimize Crabtree effect inhibition. This dynamic adjustment allows the system to achieve high cell expansion (over 100-fold) while managing the harmful effects of high sugar concentrations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces propagation costs and time, achieving high cell expansion and productivity, with cell yields increasing by more than 100 times in a single reactor stage, while minimizing the production of unwanted by-products like ethanol.
Implementation Method 1
The present invention provides additional advantages, more specifically, when associated with the propagation for second generation ethanol, but the propagation strategy described herein, in relation to optimizing the cellular biomass production, can be extended to various microorganisms, mainly microorganisms that suffer inhibition of growth by the feeding medium, for example by the Crabtree effect
Implementation Method 2
The fermentation of lignocellulosic hydrolysates is no longer a bottleneck for 2G ethanol technologies
Data Source
AI summary
The present invention relates to a method of propagating genetically modified yeasts or even any other yeasts that suffer a positive Crabtree effect or any other microorganisms that use sugars for growth (glucose or equivalent glucose), wherein the feeding medium inhibits the optimal exponential growth predicted throughout the process, such a method capable of providing greater process economicity (CAPEX and OPEX), increased productivity and yield (Yx/s) and reduced CAPEX due to greater cell expansion in a single stage of reactor. Particularly, the present invention describes a process for producing second generation ethanol by using different combinations of low-cost streams existing in an integrated 2G or 1G/2G ethanol production plant, combined with the unique batch propagation strategy fed in at least two exponential feeding phases, in just one cycle, with the propagation step occurring in a single reactor.