Filamentous Fungus Fermentation Segments Growth and Induction
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Solution Overview
Problem
Current methods for producing cellulases by Trichoderma reesei on an industrial scale face challenges such as high viscosity issues with cellulose substrates, oxygen transfer limitations, and inefficiencies in enzyme productivity, particularly when using soluble carbon sources, which restrict scalability and flexibility in bioreactor operations.
Innovation Solution
A method involving a three-step process: a batch growth phase in a stirred bioreactor, an intermediate dilution step to reduce viscosity, and a fed-batch enzyme production phase in a bubble column, allowing for optimized conditions for biomass concentration and enzyme production, with the option to overlap steps and use different reactors for each phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cellulose is used as substrate for growing Trichoderma reesei, then enzyme induction is achieved, but medium viscosity increases and oxygen transfer is disrupted
Solution Approach 1:
The fermentation process is divided into three distinct phases: (a) growth phase with soluble carbon source, (b) intermediate phase with dilution and transition, and (c) production phase with cellulose induction. This segmentation allows optimization of conditions for each phase separately, avoiding the simultaneous problems of high viscosity and poor oxygen transfer that occur when cellulose is used throughout the entire process.
Solution Approach 2:
The fungus is pre-grown in the presence of soluble carbon sources (glucose, xylose, or lactose) to achieve high biomass concentration before introducing cellulose for enzyme induction. This preliminary growth phase ensures sufficient fungal mass is present to produce high levels of enzymes when induction occurs, while avoiding the viscosity problems associated with using cellulose from the start.
2Object-affected harmful factors
If soluble carbon sources are used instead of cellulose, then oxygen transfer improves, but enzyme induction is reduced
Solution Approach 1:
Soluble carbon sources are used in the preliminary growth phase to ensure good oxygen transfer and high biomass accumulation, then cellulose is introduced in the production phase to trigger enzyme induction. This sequential use of different substrates combines the advantages of both approaches.
Solution Approach 2:
The carbon source composition is dynamically changed during the fermentation process, transitioning from soluble carbon sources to cellulose-containing substrates. This dynamic adjustment allows the system to optimize oxygen transfer during growth and enzyme induction during the production phase.
3Quantity of substance
If batch fermentation is used for growth, then biomass concentration increases, but enzyme production efficiency decreases
Solution Approach 1:
The fermentation is segmented into batch growth phase and fed-batch production phase. The batch phase maximizes biomass concentration, while the subsequent fed-batch phase with cellulose induction maximizes enzyme production efficiency, combining the advantages of both modes.
Solution Approach 2:
Biomass is preliminarily accumulated through batch fermentation with soluble carbon sources, then the system transitions to fed-batch mode with cellulose for efficient enzyme production. This preliminary biomass accumulation ensures high enzyme production capacity when induction occurs.
4Productivity
If fed-batch mode is used with continuous substrate feeding, then enzyme productivity improves, but catabolic repression increases
Solution Approach 1:
The fungus is pre-adapted to soluble carbon sources during the growth phase, then cellulose is introduced during the fed-batch production phase. This preliminary adaptation prevents catabolic repression from limiting enzyme induction, allowing continuous substrate feeding to effectively enhance productivity without the harmful repressive effects.
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 increases enzyme productivities by up to 30% and allows for more flexible and efficient industrial-scale production, reducing oxygen transfer issues and improving reactor utilization with better energy efficiency and scalability.
Implementation Method 1
a stirred and aerated bioreactor in batch phase... strictly aerobic... oxygen transfer issues
Implementation Method 2
an intermediate dilution step to reduce viscosity
Implementation Method 3
excreting an enzymatic complex which is considered to be well suited to the hydrolysis of lignocellulosic biomass
Implementation Method 4
a third step of producing enzymes from the diluted culture medium obtained in the second step (b), in the presence of at least one inductive carbon-based substrate, in fed-batch phase
Data Source
AI summary
The present invention relates to a method for producing enzymes by a strain belonging to a filamentous fungus, which comprises three steps:(a) a first step of growing biomass, in the presence of at least one carbon-based growth substrate in a stirred and aerated bioreactor (1) in batch phase,(b) a second step of diluting the culture medium obtained in the first step (a),(c) a third step of producing enzymes from the diluted culture medium obtained in the second step (b), in the presence of at least one inductive carbon-based substrate, in fed-batch phase.