Improved production of Taxol® precursors in S. cerevisiae using combinatorial in silico design and metabolic engineering

Modulating Microbial Materials - Engineering Bacterial Cellulose with Synthetic Biology

The fusion of synthetic biology and materials science offers exciting opportunities to produce sustainable materials that can perform programmed biological functions such as sensing and responding or enhance material properties through biological means. Bacterial cellulose (BC) is a unique material for this challenge due to its high-performance material properties and ease of production from culturable microbes. Research in the past decade has focused on expanding the benefits and applications of BC through many approaches. Here, we explore how the current landscape of BC-based biomaterials is being shaped by progress in synthetic biology. As well as discussing how it can aid production of more BC and BC with tailored material properties, we place special emphasis on the potential of using BC for engineered living materials (ELMs); materials of a biological nature designed to carry out specific tasks. We also explore the role of 3D bioprinting being used for BC-based ELMs and highlight specific opportunities that this can bring. As synthetic biology continues to advance, it will drive further innovation in BC-based materials and ELMs, enabling many new applications that can help address problems in the modern world, in both biomedicine and many other application fields.

Characterization of an aminotransferase TlBCAT from Trichoderma longibrachiatum UN32 involved in dendrobine-type total alkaloids biosynthesis

Trichoderma longibrachiatum UN32 is an industrially important fungus capable of producing Dendrobine-Type Total alkaloids (DTTAs). Several reports have pointed out that branched-chain amino acid aminotransferases (BCATs) participate in backbone modification or promote the production of secondary metabolites. We previously proposed that cobalt chloride increased DTTAs production in T. longibrachiatum UN32, which was associated with enhanced expression of the gene BCAT, TlBCAT (Genbank accession No. PP465542). Following cloning and characterization, the cDNA of TlBCAT was found to consists of 1191 bp, encoding a protein of 397 amino acid residues. The molecular mass of TlBCAT was about 42 kDa through SDS-PAGE analysis. The predicted pI value was 5.54. Recombinant TlBCAT can catalyze L-leu with a catalytic efficiency of 15.91 mM- 1S- 1. In the binding pocket, residues interacting with PLP, including Tyr68, Arg93, Tyr136, and Lys194, are highly conserved. TlBCAT exhibits a broad spectrum of substrate specificity, typical for catalyzing the transamination reaction of various branched-chain and hydrophobic amino acids, with α-ketoglutarate as the amino acceptor. Exogenous branched-chain amino acids (BCAAs) positively affect Trichoderma growth and DTTAs production. These findings offer insights into the physiological significance of BCAAs and present a novel approach for enhancing DTTAs production in Trichoderma mycelium cultures.

Production of pyrimidine nucleosides in microbial systems via metabolic engineering: Theoretical analysis research and prospects

Pyrimidine nucleosides, as intermediate materials of significant commercial value, find extensive applications in the pharmaceutical industry. However, the current production of pyrimidine nucleosides largely relies on chemical synthesis, creating environmental problems that do not align with sustainable development goals. Recent progress in systemic metabolic engineering and synthetic biology has enabled the synthesis of natural products like pyrimidine nucleosides through microbial fermentation, offering a more sustainable alternative. Nevertheless, the intricate and tightly regulated biosynthetic pathways involved in the microbial production of pyrimidine nucleosides pose a formidable challenge. This study focuses on metabolic engineering and synthetic biology strategies aimed at enhancing pyrimidine nucleoside production. These strategies include gene modification, transcriptional regulation, metabolic flux analysis, cofactor balance optimization, and transporter engineering. Finally, this research highlights the challenges involved in the further development of pyrimidine nucleoside-producing strains and offers potential solutions in order to provide theoretical guidance for future research endeavors in this field.

Metabolic engineering of Saccharomyces cerevisiae for enhanced taxadiene production

BACKGROUND

Metabolic engineering enables the sustainable and cost-efficient production of complex chemicals. Efficient production of terpenes in Saccharomyces cerevisiae can be achieved by recruiting an intermediate of the mevalonate pathway. The present study aimed to evaluate the engineering strategies of S. cerevisiae for the production of taxadiene, a precursor of taxol, an antineoplastic drug.

RESULT

SCIGS22a, a previously engineered strain with modifications in the mevalonate pathway (MVA), was used as a background strain. This strain was engineered to enable a high flux towards farnesyl diphosphate (FPP) and the availability of NADPH. The strain MVA was generated from SCIGS22a by overexpressing all mevalonate pathway genes. Combining the background strains with 16 different episomal plasmids, which included the combination of 4 genes: tHMGR (3-hydroxy-3-methylglutaryl-CoA reductase), ERG20 (farnesyl pyrophosphate synthase), GGPPS (geranyl diphosphate synthase) and TS (taxadiene synthase) resulted in the highest taxadiene production in S. cerevisiae of 528 mg/L.

CONCLUSION

Our study highlights the critical role of pathway balance in metabolic engineering, mainly when dealing with toxic molecules like taxadiene. We achieved significant improvements in taxadiene production by employing a combinatorial approach and focusing on balancing the downstream and upstream pathways. These findings emphasize the importance of minor gene expression modification levels to achieve a well-balanced pathway, ultimately leading to enhanced taxadiene accumulation.

Enhancing the biosynthesis of taxadien-5α-yl-acetate in Escherichia coli by combinatorial metabolic engineering approaches

Biosynthesis of paclitaxel (Taxol™) is a hot topic with extensive and durable interests for decades. However, it is severely hindered due to the very low titers of intermediates. In this study, Escherichia coli was employed to de novo synthesize a key intermediate of paclitaxel, taxadien-5α-yl-acetate (T5OAc). Plasmid-based pathway reconstruction and optimization were conducted for T5OAc production. The endogenous methylerythritol phosphate pathway was enhanced to increase the precursor supply. Three taxadien-5α-ol O-acetyltransferases were tested to obtain the best enzyme for the acetylation step. Metabolic burden was relieved to restore cell growth and promote production through optimizing the plasmid production system. In order to achieve metabolic balance, the biosynthesis pathway was regulated precisely by multivariate-modular metabolic engineering. Finally, in a 5-L bioreactor, the T5OAc titer was enhanced to reach 10.9 mg/L. This represents an approximately 272-fold increase in production compared to the original strain, marking the highest yield of T5OAc ever documented in E. coli, which is believed to be helpful for promoting the progress of paclitaxel biosynthesis.

Combinatorial biosynthesis for the engineering of novel fungal natural products

Natural products are small molecules synthesized by fungi, bacteria and plants, which historically have had a profound effect on human health and quality of life. These natural products have evolved over millions of years resulting in specific biological functions that may be of interest for pharmaceutical, agricultural, or nutraceutical use. Often natural products need to be structurally modified to make them suitable for specific applications. Combinatorial biosynthesis is a method to alter the composition of enzymes needed to synthesize a specific natural product resulting in structurally diversified molecules. In this review we discuss different approaches for combinatorial biosynthesis of natural products via engineering fungal enzymes and biosynthetic pathways. We highlight the biosynthetic knowledge gained from these studies and provide examples of new-to-nature bioactive molecules, including molecules synthesized using combinations of fungal and non-fungal enzymes.