Dissolved Oxygen Inhibits Lactic Acid in Yeast Fermentation
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Solution Overview
Problem
Lactic acid production during the conversion of lignocellulosic biomass into monosaccharides can inhibit yeast fermentation, as bacteria like Lactobacillus produce lactic acid under certain conditions, requiring a method to control lactic acid levels without adjusting temperature and pH.
Innovation Solution
Incorporating a sufficient amount of dissolved oxygen into the enzymatic hydrolysis system and yeast propagation medium to inhibit lactic acid production by bacteria, using an enzymatic hydrolysis system with cellulases to convert cellulose into oligosaccharides and monosaccharides, and maintaining optimal pH and temperature conditions for enzyme performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional enzymatic hydrolysis is used to convert cellulose into monosaccharides, then efficient conversion can be achieved, but lactic acid production by bacteria inhibits yeast fermentation
Solution Approach 1:
The patent changes the redox parameter by introducing dissolved oxygen into the system. This parameter change shifts the bacterial metabolism from anaerobic lactic acid production to aerobic respiration, eliminating lactic acid accumulation while maintaining cellulose conversion efficiency. The dissolved oxygen level is controlled to be at least 0.5 mg/L to ensure effective inhibition of lactic acid production.
Solution Approach 2:
Dissolved oxygen acts as an intermediary substance that mediates between the cellulose hydrolysis process and yeast fermentation. By introducing oxygen as an intermediate step, the system prevents the formation of harmful lactic acid without directly interfering with the enzymatic breakdown of cellulose or the subsequent yeast fermentation process.
2Object-affected harmful factors
If temperature and pH are adjusted to control lactic acid production, then bacterial activity can be suppressed, but enzyme performance and yeast propagation are negatively affected
Solution Approach 1:
Instead of changing temperature or pH parameters that affect enzyme and yeast performance, the patent changes the redox parameter by introducing dissolved oxygen. This selective parameter change targets bacterial metabolism without affecting the temperature-sensitive enzyme activity or the pH-dependent yeast fermentation process, thereby maintaining overall system reliability.
3Productivity
If dissolved oxygen is introduced to inhibit lactic acid production, then yeast fermentation can proceed efficiently, but additional process control is required
Solution Approach 1:
The system utilizes the natural solubility of oxygen in water and the existing aeration infrastructure of conventional bioreactors. Once dissolved oxygen is introduced, it automatically maintains inhibitory levels against lactic acid production throughout the hydrolysis and fermentation process, reducing the need for continuous active control while ensuring yeast fermentation efficiency.
Data Source
AI summary
Embodiments of the present disclosure involve systems and methods that inhibit the production of lactic acid during propagation of yeast and/or during hydrolysis of cellulose by including a sufficient amount of dissolved oxygen.