Intracellular Beta-Glucosidase Localization for Yeast Cellobiose Utilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Saccharomyces cerevisiae, despite its superior ethanol formation properties, is non-cellulolytic and struggles to efficiently utilize cellobiose due to extracellular cellobiose hydrolysis, which leads to feedback inhibition and contamination risks, necessitating a method for enhanced intracellular cellobiose utilization.
Innovation Solution
Transformation of yeast with a DNA sequence encoding mature β-glucosidase, specifically Saccharomycopsis fibuligera β-glucosidase (BGL1), to express the enzyme intracellularly, along with adaptation or introduction of native or heterologous disaccharide transporters to facilitate cellobiose transport into the cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If secreted β-glucosidases are expressed in S. cerevisiae to enable cellulose hydrolysis, then cellulose degradation capability is improved, but extracellular cellobiose accumulation causes feedback inhibition of endoglucanases and limits the rate and extent of cellulose hydrolysis
Solution Approach 1:
The patent extracts the harmful effect of extracellular cellobiose accumulation by redirecting the β-glucosidase enzyme action from extracellular to intracellular location. The enzyme is expressed with a mitochondrial targeting sequence, causing it to be localized inside the cell where it hydrolyzes cellobiose without accumulating in the extracellular environment, thereby eliminating feedback inhibition of endoglucanases while maintaining high cellulose hydrolysis rates
Solution Approach 2:
The patent introduces a mitochondrial targeting sequence as an intermediary element that directs the β-glucosidase enzyme to the mitochondrial compartment. This intermediary mechanism allows the enzyme to function intracellularly, serving as a mediator between the need for high cellulose degradation productivity and the avoidance of extracellular cellobiose accumulation that causes feedback inhibition
2Productivity
If secreted β-glucosidases are expressed in S. cerevisiae to enable cellulose hydrolysis, then cellulose degradation capability is improved, but the action of β-glucosidases releases glucose in the external environment that increases the risk of contamination
Solution Approach 1:
The patent extracts the harmful effect of extracellular glucose release by localizing β-glucosidase activity inside the cell. The enzyme is targeted to the mitochondria where it hydrolyzes cellobiose to glucose intracellularly, preventing glucose release into the external environment and thereby eliminating the contamination risk associated with extracellular glucose accumulation
Solution Approach 2:
The mitochondrial targeting sequence acts as an intermediary that confines the β-glucosidase enzyme and its catalytic activity within the mitochondrial compartment. This intermediary mechanism ensures that cellobiose hydrolysis and glucose release occur inside the cell rather than outside, serving as a barrier that prevents external contamination while maintaining high productivity
3Productivity
If S. cerevisiae is engineered to produce functional cellulase system for consolidated bioprocessing, then one-step conversion of cellulose to fuel ethanol is achieved, but the complexity of co-expressing multiple enzyme groups increases
Solution Approach 1:
The patent merges the functions of multiple cellulase enzyme groups (endoglucanases, exoglucanases, and β-glucosidases) into a single integrated system within the cell. By localizing β-glucosidase to the mitochondria and coordinating it with cytosolic endoglucanases and exoglucanases, the patent creates a unified enzymatic complex that processes cellulose through all four steps simultaneously, achieving consolidated bioprocessing while managing the complexity through functional integration rather than separate expression systems
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 transformed yeast strain exhibits improved cellobiose utilization, increased growth rate, and ability to hydrolyze more cellobiose than untransformed strains, with enhanced transport capabilities and phenotypic adaptations like flocculation and biofilm formation, facilitating efficient cellulose degradation.
Implementation Method 1
β-glucosidases catalyze the hydrolysis of soluble cellodextrins and cellobiose to glucose
Implementation Method 2
adaptation or introduction of native or heterologous disaccharide transporters to facilitate cellobiose transport into the cell
Implementation Method 3
fermentation of pentose sugars (end-products of hemicellulose hydrolysis) to ethanol
Data Source
AI summary
The present invention relates to methods for improving a host cell's ability to utilize the disaccharide cellobiose. In some embodiments, a transformed cell expresses intracellular β-glucosidase. In other embodiments, a transformed host cell is able to grow on media wherein cellobiose is the sole carbon source. In other embodiments, selection methods are provided which improve a host cell's ability to grow on cellobiose-containing media.