Flavonoids are natural ingredients commonly used in cosmetics, mainly for their antioxidant and anti-inflammatory effects, but they also present a variety of other biological activities such as antimicrobial, whitening, and anti-ultraviolet. Therefore, flavonoids have a huge application potential waiting to be explored. In this review, firstly, the numerous biological properties of flavonoids used in cosmetics, as well as examples of their applications in cosmetics are presented, with their biosynthetic pathways addressed. Then, recent advances in biosynthesis of typical flavonoids (e.g., phloretin, naringenin, apigenin, luteolin, chrysin, rutin, and anthocyanins) are reviewed and discussed, with a focus on the novel synthetic biology and metabolic engineering strategies to improve the productivity and yield of biosynthesized flavonoids, including the enhancement of precursor supply, characterization and modification of key enzymes, regulation of gene expression, and optimization of fermentation processes. With the continuous innovation of synthetic biology technology, there has been an increase in the efficiency of flavonoid biosynthesis and a significant reduction in production cost, which contributes substantially to the widespread use of flavonoids in cosmetics. However, the prevalence of poor solubility and low stability of flavonoids limits their applications in cosmetics. To address this issue, we outline the research process of two main strategies: nanocarrier technology and moiety modification. The application of these research results opens up new possibilities for the use of flavonoids in cosmetics. At the end, we discuss two major challenges in high-yield synthesis of complex flavonoids: the difficulty of key enzyme modification and the imbalance of metabolic flux. We also look forward to AI-assisted synthetic biology to address these challenges and drive the yield improvement and industrialization of flavonoid biosynthesis, providing biotechnological power for the development and innovation of the cosmetics industry.

Hyaluronic acid (HA), a natural linear acidic polysaccharide composed of disaccharide units of D-glucuronic acid (D-GlcA) and N-acetylglucosamine (N-GlcNAc), has been widely used in the cosmetic and medical fields. HAs with different molecular weights exhibit distinct biophysical properties. While high molecular weight HAs have stronger viscoelasticity and resistance to degradation, low molecular weight HAs demonstrate enhanced biological functions. Significant progress has been made for the industrial production of HAs, with the shift from traditional extraction from animal tissues to microbial fermentation. However, the use of the natural HA-producing species Streptococcus zooepidemicus presents challenges, such as potential pathogenicity and difficulties in molecular modifications, which limit the study on the biosynthesis of HAs with varying molecular weights. Recently, the increasing demand for specific molecular weight HAs has driven the application of metabolic engineering and synthetic biology techniques for their biosynthesis and molecular weight regulation. By identifying the key factors involved in the processes, researchers have developed various strategies to optimize the synthesis of HAs and control their molecular weights. This article first analyzes the limiting factors in the synthesis of medium and high molecular weight HAs, focusing on the genetic regulation on the synthesis pathways of HA precursors and the weakening of competitive branches. Secondly, it discusses the impact of HA synthase, precursor supply, and fermentation conditions on the synthesis of ultra-high molecular weight HAs. Finally, it summarizes the preparation strategies for low molecular weight HAs, including physical and chemical methods, enzymatic methods, and microbial direct fermentation as well. The review summarizes the latest research progress regarding challenges faced in the biosynthesis and molecular weight regulation of HAs: specifically, the insufficient molecular weight of high molecular weight HAs, the weak synthesis capability of medium molecular weight HAs, and the poor controllability of low molecular weight HAs. It provides a systematic overview on enhancing the understanding of strategies for HA biosynthesis and molecular weight regulation, aiming to facilitate the efficient biosynthesis of HAs with controlled molecular weights.

Ceramide, a fundamental bioactive molecule found ubiquitously in eukaryotic organisms, exerts profound regulatory effect on cellular physiology, encompassing critical roles in signaling cascades, cellular proliferation, differentiation, and apoptosis, as well as immunomodulation. In dermatology, ceramides play an indispensable role as constituents of the stratum corneum, the outermost layer of the skin, where they are crucial for maintaining the integrity of the epidermal barrier, regulating moisture retention, combating oxidative stress linked to aging, and exhibiting notable antimicrobial and anti-inflammatory properties. The multifaceted biological functions of ceramides underscore their extensive applications in various industries, including cosmetics, biomedicine, functional food, and animal nutrition, highlighting their significant market potential and therapeutic value. The chemical synthesis of ceramides poses substantial challenges due to the intricate stereochemistry involved, necessitating precise control over synthetic pathways. As a result, current commercial sources predominantly rely on semi-synthetic methods that integrate traditional natural extraction techniques with biochemical transformations of sphingolipid precursors to achieve targeted ceramide structures. Recent advancements in synthetic biology have explored microbial systems for the production of sphingolipids, including ceramides, offering promising avenues for scalable and sustainable synthesis. However, optimizing de novo synthesis pathways and their efficiency in microbial cell factories remains a primary research focus. Strategies aimed at enhancing ceramide yield and purity through metabolic engineering and pathway optimization are pivotal for advancing industrial applications. This paper provides a systematic review of the physiological effectiveness and function of ceramides, encompassing their physiological roles and various applications. It begins with an overview of ceramide extraction methods, including both natural extraction techniques and chemical synthesis approaches for ceramides and their precursor compounds. Subsequently, the review addresses the sphingolipid synthesis pathways and their associated key enzymes, detailing strategies for pathway regulation and optimization, as well as the aspects of product transport, storage, and secretion. Additionally, it explores the identification and expression of key enzymes. The paper concludes by examining future directions in the field, such as addressing aggregation toxicity in ceramide synthesis, enhancing transport and secretion mechanisms, advancing digital modifications of catalytic elements, and expanding gene regulatory target exploration. By synthesizing current knowledge and highlighting avenues for innovation, this review aims to catalyze further research effort toward achieving efficient ceramide production. Ultimately, optimizing ceramide synthesis has the potential to unlock its full potential in various sectors, contributing to its advancement in skincare, therapeutics, and functional materials. The integration of microbial systems is particularly promising for expanding production capabilities while addressing sustainability concerns in ceramide manufacturing. Continued advancements in synthetic biology and biotechnology are expected to revolutionize the landscape of ceramide applications, paving the way for enhanced therapeutic interventions and novel industrial applications in the future.

The demand for personal care products has been increasing steadily. Consumers are now seeking for products that offer enhanced functionality, natural ingredients, and superior feeling experiences. Fragrances and flavors are key components in personal care formulations. Terpenes and their derivatives dominate natural fragrances due to their diverse structures and scents, widespread availability from plants and animals, stable function, and high safety profile. The terpene fragrance market is projected to grow at an annual growth rate of 6.4%, reaching $1.01 billion by 2028, indicating a high market revenue and promising future. Currently, the acquisition of natural terpene fragrances is constrained by the long growth cycle of plants, low terpene content, and high extraction cost. Thus, there is an urgent need for developing new technology, such as synthetic biology, to achieve large-scale production of diverse fragrance compounds at an environment-friendly manner. This review explores the application and development of synthetic biology in the sustainable production of terpene fragrances, highlighting how data-driven synthetic biology and biotechnological innovations empower terpene fragrance production. It also compares classical and alternative terpenoid biosynthesis pathways, elucidating their differences and advantages, which can offer comprehensive insights for chassis design toward terpenoid efficient biosynthesis. Additionally, this review explores recent advances in terpene synthase discovery and engineering as well as cell factory construction. Furthermore, we comprehensively summarizes challenges encountered in the construction of three major types of terpene fragrance cell factories: monoterpenes, sesquiterpenes, and nor-isoprenoids, and discusses metabolic engineering strategies that can be employed to address these issues, including enzyme optimization, pathway reconstruction, and cellular detoxification. At the end, we comment the current landscape of patents and industrial competition, offering insights into future challenges and opportunities, including the hurdles of biosynthesis technology, the discovery and design of new products, as well as the market regulation and safety concerns.

DNA data storage is a key for the development and application of synthetic biology. With the advent of high density storage technology for long period and more stable and secure data storage, the shortage of storage capacity caused by the explosive growth of data can be addressed. Thus, exploring the legal issues for the storage of DNA data is more important than ever for ethics with the emerging science and technology. At the human rights level, human dignity and privacy need to be protected, and the data gap between human beings available and unavailable to the data to be minimized, through the development of complete policy and legal systems for DNA data storage. At the security level, it is suggested to strengthen the security governance of DNA data storage technology by combining information security and biosafety issue. At the level of intellectual property, it is suggested to improve patent protection, and optimize the legal environment of intellectual property, so as to promote the technological innovation and application of DNA data storage technology.

With the socioeconomic development, the dependence of human beings on fossil fuels has led to their shortage and climate change. This has created an urgent need for alternatives that are renewable and environmentally friendly, and biofuels are one of them. Nowadays, widely recognized biofuels like fuel ethanol and biodiesel face challenges in terms of their production capacity due to limitation on raw materials such as grains and edible oils and high cost as well. Hence, the integration of metabolic engineering and synthetic biology has opened avenues for utilizing diverse substrates from other renewable sources, such as solar energy, light energy, electric energy, and waste biomass. Microbial cell factories, including microalgae, bacteria, and yeast, play a crucial role in synthesizing biofuels. The review comments on the evolution of the four generations of biofuels, encompassing fuel ethanol, biodiesel, bio-gasoline, jet and aviation fuels. We also discuss how microorganisms can be explored for producing the third- and fourth-generation biofuels from a variety of unconventional substrates such as carbon dioxide, methanol, and methane, multi-energy coupling to synthesize biofuels from lignocellulose by bacterial or yeast, CO₂ conversion by microalgae or electrochemical-biological systems, the conversion of methanol and methane by methyltrophic microbes, and the application of synthetic biology. Furthermore, we overview biosynthetic pathways and engineering strategies for optimizing biofuels production. These strategies can convert raw materials to various fuel products, including fatty acids and esters, advanced alcohols and esters, isoprenoids, and polyketides. Finally, we highlight some challenges in biofuels production, including raw material supply and cost issue, low production yield, and limited product variety. Meanwhile, to address these challenges, we propose corresponding solutions. For example, by optimizing carbon fixation pathways, and converting carbon dioxide into low-carbon substrates like methanol, autotrophic microorganisms, methylotrophic microorganisms, and other cell factories can utilize carbon dioxide as the major raw material to synthesize various biofuels, which can benefit the application of biofuels and further promote their industrial production.

Non-renewable resources, such as petrochemicals, have made great contributions to modern civilization. However, the extensive use of fossil fuels, which have been buried for hundreds of millions of years, has led to a substantial increase in carbon imbalance. The imbalance leads to severe ecological and environmental problems. Industrial biomanufacturing, often referred to as a “sunshine economy”, represents a novel sustainable production paradigm, utilizing renewable resources in a carbon-cycling mode. This paper discusses several ways in which biomanufacturing can support China’s “carbon peaking and carbon neutrality” goals from the perspectives of manufacturing feedstock, production mode and product usage. Biomanufacturing can reduce carbon emissions through feedstock substitution, technology iteration and product replacement. Utilization of straw biomass, producing non-food proteins and establishing a biobased industry landscape are important approaches for reducing carbon emissions in biomanufacturing. Efficient biomanufacturing of food and natural products can substantially improve production efficiency, conserve significant land resources, and thus provide land resources for “carbon replacement”. Optimizing agricultural products through biotechnology advancements and innovative product development is a crucial way to reduce pollution but also enhance the carbon sink capacity of the agricultural sector.

Glucoraphanin (GRA), a secondary metabolite of plants, is a glucosinolate (GSL) derived from methionine. It is relatively stable in nature, and both GRA and its degradation product sulforaphane (SFN) play important roles in anticancer, neuroprotection, and other broad biological functions and health-benefits, and in particular, SFN has been reported as the best natural product for anticancer. In this article, we review the physicochemical properties, sources, biological functions, synthetic pathways, current production status of GRA, and discuss the potential strategy for the efficient biological synthesis of GRA in the future. The synthesis pathway of GRA involves three stages: side chain elongation, core structure information, and side chain modification. GRA can be converted into SFN and other active compounds by plant myrosinase (MYR) and intestinal microorganisms. Brassicaceae crops such as broccoli have high levels of GRA, and are currently the main source of GRA. However, the cultivation cycle of GRA-rich plants is long, and its extraction yield is low. Therefore, the development of economical and renewable new resources of GRA will greatly advance its applications. With the elucidation of the biosynthesis and regulation pathways of GRA, its genetic engineering-assisted efficient biological synthesis shows great potential, suggesting that the possibility for developing strategies with the manipulation of multiple genes for regulated expression at different dimensions to synthesize GRA more efficiently compared to the current mainstream strategy through manipulating single genes. This review focuses on the genetic engineering-assisted efficient biosynthesis of GRA in Brassicaceae crops, systematically outlining potential genes for engineering at each stage of GRA synthesis and highlights chassis crop species from the perspective of enrichment organs, aiming to providing ideas and strategies for the future regulation of GRA biosynthesis in plants through transgenic technology and molecular breeding for large-scale sustainable production of GRA.

The CRISPR-Cas gene editing technology has revolutionized the fields of biology, medicine, agronomy, etc. due to its simplicity and efficiency. Laboratory-developed tools, such as the widely recognized CRISPR-Cas9, have played a pivotal role in addressing a multitude of genetic diseases. By harnessing the targeted nucleic acid capabilities of the CRISPR-Cas system, researchers have successfully integrated various functionalities into Cas proteins, including fluorescent markers, transcriptional regulatory proteins, and base editing components. This has unlocked new possibilities, including chromosome imaging, transcriptional regulation, and precise base editing. Currently, Cas nucleases with large molecular weights, often exceeding 1000 amino acids, are commonly used. However, adeno-associated virus (AAV) vectors, which are extensively employed in gene therapy, have limited capacity to accommodate additional functional components beyond the coding sequences of CRISPR nucleases and guide RNAs (gRNAs). This limitation severely constrains their utilization in gene therapy and other applications. As a result, a significant focus of research has been placed on the miniaturization of CRISPR tools, making them compact enough to align with current delivery methods. Compact Cas protein variants within CRISPR-Cas systems hold the potential to create and deliver genome editing and regulatory tools into human cells using AAV. Hence, the development of miniaturized CRISPR-Cas systems presents a crucial avenue for addressing this technical challenge. This article provides a comprehensive review of research progress in miniaturizing key proteins within two classes of Cas systems: Cas9 and Cas12 for targeting DNA, and Cas13 for targeting RNA. This review encompasses the screening of novel Cas proteins, the reduction of protein structural domains, and the modification of guide RNAs, all with the intention of presenting innovative ideas for the further advancement of compact, precise gene editing, and regulatory tools. The miniaturization of CRISPR-Cas systems is a critical step toward unlocking their full potential in various fields, including biomedicine, agriculture, and basic research. As researchers continue to explore and refine these compact gene editing and regulatory tools, we can expect significant advancement in understanding and manipulating genetic information. This ongoing progress promises to have a profound impact on the future of science and technology. At present, the limitations of the miniaturized CRISPR-Cas system are mainly with the size of protein molecular weight and the efficiency and specificity of gene editing. If we can solve these problems and obtain a smaller structure in future research, not only can we optimize the transmission of the system in the body, but also develop high-efficiency and low-damage treatment methods for clinic applications.

The inquiry into the essence of organisms has long been a thriving topic in biology and philosophy. Hypothesises are commonly employed in biological research to understand lives. These hypothesises can be grouped into two categories: ① the machine hypothesis, likening the components and organizational structure of organisms to the operation of machines, and ② the autopoietic hypothesis, likening organisms to complex systems with purposeful and unique attributes. Both play an epistemic role in various fields of biology, serving as theoretical hypotheses, heuristic tools, and means of scientific communication. The machine hypothesis, for instance, has been influential in areas such as molecular biology and systems biology, where organisms are viewed as intricate machines made up of interacting components. The autopoietic hypothesis, on the other hand, has been more prominent in theoretical biology and philosophy of biology, highlighting the self-organizing and self-producing nature of living systems. The development of synthetic biology, which aims to redesigning and constructing biological systems from scratch, has challenged the traditional dichotomy between natural and artificial entities. Both the machine and autopoietic hypothesises are reflected in the advancement of synthetic biology, as researchers attempt to engineer living systems using principles and methods adapted from various disciplines, including engineering, computer science, and materials science. While the hypothesises serve epistemic purposes, their usage also raises some controversies, particularly in the context of synthetic biology. The conflation of ontology and epistemology, where hypothesises are mistaken for literal descriptions of reality, can lead to ethical concerns. For example, the machine hypothesis may suggest that organisms are merely complicated machines to be manipulated, potentially diminishing their intrinsic value and ethical status. This article examines the origin and clarification of these two hypothesises, their applications in synthetic biology, and addresses the potential confusions and ethical implications arising from their usage. It advocates for a cautious approach to the usage of the epistemological hypothesis, considering both its epistemic impact and ethical consequence. As synthetic biology continues to advance, it is crucial to maintain a critical and nuanced understanding of hypothesises employed, recognizing their heuristic value while also acknowledging their limitations and potential pitfalls. The discussion of hypothesises for organism origins in the context of synthetic biology highlights the importance of interdisciplinary collaboration and dialogue between scientists, philosophers, and ethicists. By examining the philosophical and ethical issues of hypothesises, we can better navigate the complex and rapidly evolving landscape of synthetic biology, ensuring that our scientific endeavors are guided by a deep appreciation for the intricate and multifaceted nature of lives.