Key metabolic engineering strategies, including biosynthetic pathway engineering, cluster-specific channeling of geranylgeranyl diphosphate biosynthesis, cofactor engineering, as well as regulatory mechanisms involving nitrogen modulation and histone modification are highlighted.
Abstract
Gibberellic acids (GAs) are a class of tetracyclic diterpene carboxylic acid compounds produced by green plants, fungi, and bacteria, which have a wide range of applications in agricultural production and food ingredients processing. Owing to the continuously growing market demand, enhancing GA yield has become imperative. The biosynthesis of GAs is a multi-enzymatic synergistic process that can be enhanced through genetic and metabolic engineering strategies. In this review, we first summarize recent advances in GA production by Fusarium fujikuroi. We then highlight key metabolic engineering strategies, including biosynthetic pathway engineering, cluster-specific channeling of geranylgeranyl diphosphate biosynthesis, cofactor engineering, as well as regulatory mechanisms involving nitrogen modulation and histone modification. Finally, we discuss promising approaches for constructing high-efficiency microbial cell factories, such as implementation of the CRISPR/Cas9 system, the application of strong promoters, the development of target-specific technologies for small molecules, and the employment of genome-scale metabolic models. Recent metabolic engineering efforts have achieved GA3 titers of up to 3.16 g/L through multi-target nitrogen regulation strategies, highlighting the potential for further yield improvement.
Betalains are water-soluble pigments containing nitrogen, and they exist naturally in the plants of the order Caryophyllales. They have gained increasing attention in recent years because of their intense colours, antioxidant activity, and safety, thus making them suitable replacements for artificial dyes. The increasing interest in natural pigments has led to intensified research on betalain biosynthesis and optimization of pigment production. Nonetheless, their application in industry faces limitations, such as their low natural occurrence, sensitivity to environmental conditions, and instability during manufacturing and storage. Unlike previous reviews that primarily focused on betalain chemistry, biosynthesis pathways, or biological activity, the present review highlights recent developments in the engineering of the biosynthesis pathways, synthetic biology, elicitation approaches, omics-based pathway identification, and nanobiotechnology for betalain pigments. Special attention is paid to the comparison of plant, plant cell, yeast, and bacterial production systems, as well as recent advancements towards industrial production of betalain pigments and bottlenecks in the commercialization of sustainable betalain bio-factories.
S. Monisha, M. Kanchana, Aiyar Balasubramanian et al.· BioTech· 0 citations
Forskolin, a labdane-type diterpenoid isolated from Coleus forskohlii, exhibits therapeutic potential for osteoporosis, cardiovascular diseases, and metabolic syndrome. Its rising nutraceutical demand and limited natural availability have driven synthetic biology approaches for sustainable production. Although significant efforts have been devoted to upstream pathway optimization, the improvement of the downstream pathway still faces challenges due to the complex metabolic network and the low catalytic activity of cytochrome P450s (P450s). In this study, we elucidated the biosynthetic network involved in forskolin production, in which three P450s mediate multi-site oxidation, providing critical pathway insights for forskolin biosynthesis. Based on this, we reconstructed an efficient biosynthetic pathway of forskolin in yeast and subsequently optimized its production efficiency through multidimensional engineering strategies including central carbon flux optimization, rate-limiting enzyme engineering, P450 electron transfer chain reinforcement, and fermentation optimization. The final strain achieved the production of 2.7 g/L forskolin in a 5-L bioreactor, which represents the highest titer reported to date. This study establishes a microbial platform for forskolin production and provides advancements in the complex network of plant natural product biosynthesis.
Meiling Jiang, Hao Tang, Ying Ma et al.· Bioresource Technology· 0 citations
Artificial intelligence (AI) and machine learning (ML) have emerged as powerful tools for metabolic engineering by enabling pathway prediction, metabolic flux optimization, enzyme engineering, and identification of bottlenecks throughout terpenoid biosynthesis.
Aakash Kamalesan, K. Kumar, Bharathi Nathan et al.· Antonie van Leeuwenhoek· 0 citations
Astaxanthin, a C40 carotenoid with exceptional antioxidant, anti-inflammatory, and anticancer physiological activities, has experienced surging market demand across cosmeceutical, food, and pharmaceutical industries. Traditional astaxanthin production methods have critical limitations, including high costs, significant environmental impact, limited scalability, and stereochemical inadequacies, underscoring the urgent need for alternative production platforms. Metabolic engineering of industrial microorganisms provides a paradigm-shifting solution, leveraging rapid growth, genetic tractability, scalable fermentation, and climate-independent production to achieve sustainable, cost-effective astaxanthin biosynthesis. In this review, we comprehensively review the metabolic engineering strategies employed in non-native astaxanthin producers for higher production of astaxanthin, including directing carbon fluxes toward astaxanthin productivity, balanced expression of either engineered or non-engineered enzymes, their compartmentalization, morphology, and membrane engineering, cofactors, and precursor optimization. Additionally, we highlight emerging technologies aimed at overcoming current bottlenecks faced by non-native producers to advance their industrial applicability and further boost astaxanthin yields toward industrial competitiveness.
Oleaginous yeasts, particularly Yarrowia lipolytica, are increasingly used as microbial platforms for producing lipids and other value-added compounds from renewable feedstocks. Their biotechnological utility derives from active lipid metabolism, broad substrate flexibility, and expanding engineering tools, but efficient production requires transcriptional programs that match changing metabolic states during fermentation. Because carbon flux is redistributed across growth, nutrient limitation, lipid accumulation, and production phases, static constitutive expression is often insufficient for optimal pathway performance. Promoter engineering therefore provides a key strategy to control expression strength, timing, and responsiveness in oleaginous yeasts. This review summarizes the metabolic basis of phase-dependent gene expression demand, examines constitutive, inducible, and dynamic promoter systems, and discusses how machine learning can support promoter prediction and design. Current challenges, including limited host-specific datasets, context dependence, and uncertain robustness to scale-up, are also discussed. These advances provide a basis for more precise and scalable engineering of oleaginous yeast cell factories.
Akhmad Awaludin Agustiar, Zewei Lu, Dianqi Yang et al.· Biotechnology Advances· 0 citations
Polyketides are among the most structurally diverse and therapeutically important classes of natural products, serving as antibiotics, anticancer agents, agrochemicals, and industrial pigments. Their structural complexity and limited natural availability have driven the development of microbial biosynthetic platforms as scalable and sustainable alternatives to traditional extraction or chemical synthesis. Yarrowia lipolytica, a non-conventional and metabolically versatile yeast, has emerged as a promising alternative chassis for polyketide biomanufacturing, owing to its streamlined central metabolism, high acetyl-CoA availability, and exceptional physiological robustness. Recent advances in metabolic engineering and synthetic biology have enabled extensive rewiring of Y. lipolytica metabolism to support the high-yield production of complex, high-value polyketides. This review summarizes state-of-the-art strategies, from classical metabolic rewiring to emerging approaches such as organelle engineering and subcellular compartmentalization. We further highlight representative case studies of polyketide biosynthesis in Y. lipolytica, critically assess current limitations, and explore future directions to establish this organism as a programmable, industrially viable platform for polyketide production.
