Bioethanol Production via Partial Lignin Removal and Re-acidification
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Solution Overview
Problem
Current bioethanol production from lignocellulosic vegetable raw material faces challenges such as high costs due to expensive cellulases, long hydrolysis times, and enzyme inhibition by lignin and hemicellulose-derived compounds, particularly when using enzymatic hydrolysis and fermentation processes.
Innovation Solution
A process involving partial elimination of lignins using sodium hydroxide treatment followed by washing, and re-acidification with a mixture of acetic and formic acid to achieve a specific residual lignin level, optimizing conditions for enzymatic hydrolysis and fermentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If total elimination of lignins is performed before enzymatic hydrolysis, then enzyme inhibition is reduced, but hydrolysis efficiency does not reach maximum and production costs increase
Solution Approach 1:
The patent applies partial elimination of lignins rather than total elimination. The process reduces lignin content to a specific residual level (0.05-5% dry matter) which is sufficient to maintain hydrolysis efficiency while removing enough lignin to prevent enzyme inhibition. This partial action optimizes the balance between removing harmful substances and preserving beneficial structural elements.
Solution Approach 2:
The patent changes the parameter of lignin residual level from near-zero (conventional approach) to a controlled range (0.05-5% dry matter). By adjusting this parameter, the process achieves maximum hydrolysis efficiency while preventing enzyme inhibition, demonstrating that an optimal intermediate value exists rather than requiring complete elimination.
2Reliability
If conventional pretreatment methods are used to remove lignins, then enzyme inhibition is reduced, but the process becomes complex and costly
Solution Approach 1:
The patent merges the lignin elimination step with the existing pretreatment process. The pretreatment conditions (temperature, pH, time) are optimized to simultaneously achieve both lignin removal and cellulose preparation for hydrolysis in a single integrated process, eliminating the need for separate lignin removal steps and reducing overall process complexity.
Solution Approach 2:
The pretreatment process is designed to perform multiple functions simultaneously: it breaks down the lignocellulosic structure, removes lignins to prevent enzyme inhibition, and prepares cellulose for efficient hydrolysis. This multi-functionality reduces the number of separate process steps and equipment requirements.
3Productivity
If high cellulase activity is used to achieve maximum hydrolysis, then hydrolysis speed increases, but production costs increase due to expensive enzymes
Solution Approach 1:
The patent performs preliminary elimination of lignins before the enzymatic hydrolysis step. By removing lignins in advance, the cellulose substrate is prepared to be more accessible and receptive to enzyme action, which increases hydrolysis efficiency and allows for reduced enzyme dosage while maintaining high productivity.
Solution Approach 2:
The patent changes the substrate parameter (lignin content) to optimize enzyme performance. By controlling lignin residual levels within the optimal range, the hydrolysis process achieves maximum efficiency with lower enzyme concentrations, reducing the quantity of expensive enzymes required.
4Device complexity
If lignin residual levels are kept high in the substrate, then process simplicity is maintained, but enzyme inhibition occurs and hydrolysis efficiency decreases
Solution Approach 1:
The patent applies partial elimination of lignins rather than maintaining high levels. By removing lignins to a controlled residual level (0.05-5% dry matter), the process achieves sufficient lignin reduction to prevent enzyme inhibition while avoiding the complexity and costs of complete elimination, optimizing the balance between simplicity and efficiency.
Data Source
Figure 1~2
AI summary
The invention concerns a process for producing bioethanol comprising the steps of pretreatment (consisting in destructuring the lignocellulosic vegetable raw material by placing it in the presence of a mixture containing formic acid, acetic acid and water, then in separating cellulose), of enzymatic hydrolysis and of alcoholic fermentation, characterized in that it comprises, prior to the enzymatic hydrolysis, a step of partial elimination of the lignins so as to obtain a residual overall level of lignins (T), expressed as percentage by weight, which is non-zero and which is included in a range determined by a lower limit, and an upper limit Bsup, respectively equal to 0.30% and 4%. In order to obtain conditions of acidification before the enzymatic hydrolysis step, the process comprises a step for re- acidification of the mixture, which is carried out by means of an acid, or of a mixture of acids, of determined pKa, and in particular by means of weak organic acids such as acetic acid and/or formic acid.