Improvement of Large-Scale Production of Lignocellulosic Bioethanol through Synthetic Biology Approaches: A Comprehensive Review

Abstract

This review article explores the use of synthetic biology approaches like gene editing and metabolic engineering to create genetically-modified organisms that can produce commercially-valuable products on large-scale, clean environmental pollutants, and serve as efficient biosensors. The Biobrick system includes a registry of available genetic information and a set of standard protocols for assembling and testing them, which finds various significant uses in synthetic biology, such as in the production of "Fourth generation” biofuel. Genetic engineering techniques may be applied to manipulate crops or microbes for more efficient biofuel production. Such synthetic biology techniques also include modification of lignin structure and content, use of bacterial enzymes abundantly expressed in plants, and manipulation of hemicellulose biosynthesis. However, challenges such as high temperature, efficient conversion of all substrate molecules for maximum product yield, efficient pentose fermentation, and tolerance to acetic acid and bioethanol concentration can all impact the yield of the product. This article explores innovative genetic modification approaches designed to decrease lignin levels and enhance crop digestibility in plants, with a specific focus on the model plant Arabidopsis thaliana and herbaceous plants such as Alfalfa. The aim is to manipulate the Monolignol pathway and modify the CSE gene, known for its ability to decrease lignin content. These modifications have been shown to significantly improve saccharification efficiency and increase the yield of lignocellulosic bioethanol. Besides, the role of xylulose-5-phosphate as an intermediate in the non-oxidative pentose phosphate pathway and the oxidative pentose phosphate pathway, and the use of heterologous xylose transporters and modified sugar transporters as potential solutions to improve the biofuel production efficiency is also discussed in this review article.