Biofuels and bio-based chemicals from lignocellulose: metabolic engineering strategies in strain development

Abstract

Interest in developing a sustainable technology for fuels and chemicals has unleashed tremendous creativity in metabolic engineering for strain development over the last few years. This is driven by the exceptionally recalcitrant substrate, lignocellulose, and the necessity to keep the costs down for commodity products. Traditional methods of gene expression and evolutionary engineering are more effectively used with the help of synthetic biology and -omics techniques. Compared to the last biomass research peak during the 1980s oil crisis, a more diverse range of microorganisms are being engineered for a greater variety of products, reflecting the broad applicability and effectiveness of today's gene technology. We review here several prominent and successful metabolic engineering strategies with emphasis on the following four areas: xylose catabolism, inhibitor tolerance, synthetic microbial consortium, and cellulosic oligomer assimilation.

Utilization of xylose by engineered strains of Ashbya gossypii for the production of microbial oils

“…The importance of the present work relies on the feasibility of A. gossypii as a cell factory, which enables the application of systems metabolic engineering, fluxomics, and model-based approaches for the generation of improved strains with broad-range abilities for microbial fermentations. A large number of applications for the use of xylose-rich lignocellulosic feedstocks are being recently reported such as the production of ethanol, butanol, butanediol, hexadecanol, and organic acids [40–43]. Hence, it is worthy to mention that enabling A. gossypii to use xylose as the only carbon source opens new opportunities for the harnessing of xylose-rich substrates not only for the production of microbial oils, but also a wide range of high-value industrial products such as fine chemicals, riboflavin and other vitamins, purines, and xylitol.…”

Enhanced fermentative performance under stresses of multiple lignocellulose-derived inhibitors by overexpression of a typical 2-Cys peroxiredoxin from Kluyveromyces marxianus

“…Therefore, exploring the toxicity of distinctive inhibitors to cells and its mechanism, and developing excellent strains with enhanced tolerance are becoming a more critical component of ethanol production from lignocellulosic materials. However, mechanisms of toxicities of these inhibitors in yeasts are very complex and greatly variable depending on strains [3]. …”

Fungal Enzymes for Bio-Products from Sustainable and Waste Biomass

“…Since biofuels are not always cost competitive with fossil fuels [53], glucose is increasingly used for the production of platform chemicals (i.e. chemicals that serve as a convenient starting material for the synthesis of various products) [54]. New information from genome sequencing and advances in sophisticated techniques for metabolic engineering have allowed the development of robust and efficient strains capable of converting lignocellulose hydrolysates to platform chemicals.…”