ALDC Enzyme Stability in Low Malt Fermentation
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Solution Overview
Problem
Diacetyl, a by-product of fermentation, negatively affects the flavor and taste of beer due to its strong odor, and existing methods for reducing its formation, such as using acetolactate decarboxylase (ALDC) enzymes, face stability issues, especially in fermenting worts with low malt content.
Innovation Solution
The development of Bacillus host cells with genetic alterations that decrease the production of endogenous proteases and overexpress ALDC enzymes, enhancing their stability and activity, allowing for improved recovery and utilization in fermentation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ALDC enzyme is added during fermentation to convert acetolactate into acetoin, then diacetyl formation is prevented and flavor is improved, but the ALDC enzyme becomes unstable especially in fermenting worts with low malt content
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of the ALDC enzyme through site-directed mutagenesis. Specific amino acid residues are substituted to enhance the enzyme's stability and activity under fermenting conditions, particularly in low malt content worts where the enzyme previously showed instability. This direct modification of molecular parameters resolves the contradiction between maintaining reliability and adapting to varying wort compositions.
2Reliability
If protease production is high in Bacillus host cells, then the host cells can degrade proteins for nutrient availability, but the ALDC enzyme stability is reduced due to proteolytic degradation
Solution Approach 1:
The patent applies the taking out principle by genetically deleting or inactivating specific protease genes (vpr, wprA, and other extracellular and intracellular proteases) in the Bacillus host cell. This removal of harmful proteolytic elements prevents degradation of the ALDC enzyme, thereby enhancing its stability and activity during fermentation without compromising the host cell's overall protein metabolism.
Solution Approach 2:
The patent converts the harmful effect of proteases (which degrade the ALDC enzyme) into a benefit by creating a protease-deficient host strain. The genetic modifications eliminate proteolytic activity that would otherwise destabilize the ALDC enzyme, transforming the host cell environment from one that degrades the enzyme to one that protects and stabilizes it, thereby improving overall fermentation performance.
3Productivity
If standard ALDC production methods are used, then the process is simple, but the yield of recoverable ALDC enzyme is low
Solution Approach 1:
The patent applies preliminary action by pre-modifying the Bacillus host cell genome to delete protease genes and optimize the expression system before introducing the ALDC gene. This preparatory genetic engineering creates a host environment that is primed for high-level ALDC production with enhanced stability, allowing for higher enzyme yields without requiring complex downstream processing or purification steps.
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
The modified ALDC enzymes demonstrate improved stability and activity, effectively reducing diacetyl levels in beer, thereby enhancing the flavor and aroma, and can be recovered in higher yields, simplifying the fermentation process.
Implementation Method 1
Acetolactate decarboxylase (ALDC) can also be used as an enzyme to prevent the formation of diacetyl. α-acetolactate can be converted into acetoin by adding an ALDC enzyme during fermentation.
Data Source
AI summary
The present disclosure provides methods, compositions, apparatuses, and kits comprising ALDC enzymes having a better stability and activity, and which further can be recovered from microorganisms in improved yields.