利用海洋硅藻生产生物活性物质研究进展*

生物活性物质在食品、饵料、化妆品、保健品和医药等行业具有广阔的应用前景,其研究早已受到广泛关注。鉴于海洋硅藻具有生长速度快、生物活性物质含量高、易于规模培养、便于提取等诸多优势,为理想的生物活性物质生产者。尽管国内外已进行了大量利用海洋硅藻生产生物活性物质的研究,但是受限于培养工艺老旧、生产成本过高等缺陷,商业化利用海洋硅藻开发生物活性物质依然停滞不前。阐述海洋硅藻五种常见生物活性物质的应用价值,进一步探讨海洋硅藻高产生物活性物质的策略,就如何低成本、高效开发利用硅藻源生物活性物质提出建议,为海洋硅藻商业化开发利用提供参考。     

Diversity and biotechnological potential of the sponge-associated microbial consortia

Sponges are well known to harbor diverse microbes and represent a significant source of bioactive natural compounds derived from the marine environment. Recent studies of the microbial communities of marine sponges have uncovered previously undescribed species and an array of new chemical compounds. In contrast to natural compounds, studies on enzymes with biotechnological potential from microbes associated with sponges are rare although enzymes with novel activities that have potential medical and biotechnological applications have been identified from sponges and microbes associated with sponges. Both bacteria and fungi have been isolated from a wide range of marine sponge, but the diversity and symbiotic relationship of bacteria has been studied to a greater extent than that of fungi isolated from sponges. Molecular methods (e.g., rDNA, DGGE, and FISH) have revealed a great diversity of the unculturable bacteria and archaea. Metagenomic approaches have identified interesting metabolic pathways responsible for the production of natural compounds and may provide a new avenue to explore the microbial diversity and biotechnological potential of marine sponges. In addition, other eukaryotic organisms such as diatoms and unicellular algae from marine sponges are also being described using these molecular techniques. Many natural compounds derived from sponges are suspected to be of bacterial origin, but only a few studies have provided convincing evidence for symbiotic producers in sponges. Microbes in sponges exist in different associations with sponges including the true symbiosis. Fungi derived from marine sponges represent the single most prolific source of diverse bioactive marine fungal compounds found to date. There is a developing interest in determining the true diversity of fungi present in marine sponges and the nature of the association. Molecular methods will allow scientists to more accurately identify fungal species and determine actual diversity of sponge-associated fungi. This is especially important as greater cooperation between bacteriologists, mycologists, natural product chemists, and bioengineers is needed to provide a well-coordinated effort in studying the diversity, ecology, physiology, and association between bacteria, fungi, and other organisms present in marine sponges.     

The current status of natural products from marine fungi and their potential as anti-infective agents

A growing number of marine fungi are the sources of novel and potentially life-saving bioactive secondary metabolites. Here, we have discussed some of these novel antibacterial, antiviral, antiprotozoal compounds isolated from marine-derived fungi and their possible roles in disease eradication. We have also discussed the future commercial exploitation of these compounds for possible drug development using metabolic engineering and post-genomics approaches.     

BIOACTIVE PROTEINS,PEPTIDES, AND AMINO ACIDS FROM MACROALGAE1

Macroalgae are a diverse group of marine organisms that have developed complex and unique metabolic pathways to ensure survival in highly competitive marine environments. As a result, these organisms have been targeted for mining of natural biologically active components. The exploration of marine organisms has revealed numerous bioactive compounds that are proteinaceous in nature. These include proteins, linear peptides, cyclic peptides and depsipeptides, peptide derivatives, amino acids, and amino acid–like components. Furthermore, some species of macroalgae have been shown to contain significant levels of protein. While some protein‐derived bioactive peptides have been characterized from macroalgae, macroalgal proteins currently still represent good candidate raw materials for biofunctional peptide mining. This review will provide an overview of the important bioactive amino‐acid‐containing compounds that have been identified in macroalgae. Moreover, the potential of macroalgal proteins as substrates for the generation of biofunctional peptides for utilization as functional foods to provide specific health benefits will be discussed.     

Systematics-guided bioprospecting for bioactive microbial natural products

Advances in the taxonomic characterization of microorganisms have accelerated the rate at which new producers of natural products can be understood in relation to known organisms. Yet for many reasons, chemical efforts to characterize new compounds from new microbes have not kept pace with taxonomic advances. That there exists an ever-widening gap between the biological versus chemical characterization of new microorganisms creates tremendous opportunity for the discovery of novel natural products through the calculated selection and study of organisms from unique, untapped, ecological niches. A systematics-guided bioprospecting, including the construction of high quality libraries of marine microbes and their crude extracts, investigation of bioactive compounds, and increasing the active compounds by precision engineering, has become an efficient approach to drive drug leads discovery. This review outlines the recent advances in these issues and shares our experiences on anti-infectious drug discovery and improvement of avermectins production as well.     

酿酒酵母代谢工程技术

自20世纪90年代初期诞生以来,代谢工程历经了30年的快速发展。作为代谢工程的首选底盘细胞之一,酿酒酵母细胞工厂已被广泛应用于大量大宗化学品和新型高附加值生物活性物质的生物制造,在能源、医药和环境等领域取得了巨大的突破。近年来,合成生物学、生物信息学以及机器学习等相关技术也极大地促进了代谢工程的技术发展和应用。文中回顾了近30年来酿酒酵母代谢工程重要的技术发展,首先总结了经典代谢工程的常用方法和策略,以及在此基础上发展而来的系统代谢工程和合成生物学驱动的代谢工程技术。最后结合最新技术发展趋势,展望了未来酿酒酵母代谢工程发展的新方向。     

Major bioactive metabolites from marine fungi: A Review

Biologists and chemists of the world have been attracted towards marine natural products for the last five decades. Approximately 16,000 marine natural products have been isolated from marine organisms which have been reported in approximately 6,800 publications, proving marine microorganisms to be a invaluable source for the production of novel antibiotic, anti tumor, and anti inflammatory agents. The marine fungi particularly those associated with marine alga, sponge, invertebrates, and sediments appear to be a rich source for secondary metabolites, possessing Antibiotic, antiviral, antifungal and antiyeast activities. Besides, a few growth stimulant properties which may be useful in studies on wound healing, carcinogenic properties, and in the study of cancers are reported. Recent investigations on marine filamentous fungi looking for biologically active secondary metabolites indicate the tremendous potential of them as a source of new medicines. The present study reviews about some important bioactive metabolites reported from marine fungal strains which are anti bacterial, anti tumour and anti inflammatory in action. It highlights the chemistry and biological activity of the major bioactive alkaloids, polyketides, terpenoids, isoprenoid and non-isoprenoid compounds, quinones, isolated from marine fungi.     

Systematic and biotechnological aspects of halophilic and halotolerant actinomycetes

More than 70 species of halotolerant and halophilic actinomycetes belonging to at least 24 genera have been validly described. Halophilic actinomycetes are a less explored source of actinomycetes for discovery of novel bioactive secondary metabolites. Degradation of aliphatic and aromatic organic compounds, detoxification of pollutants, production of new enzymes and other metabolites such as antibiotics, compatible solutes and polymers are other potential industrial applications of halophilic and halotolerant actinomycetes. Especially new bioactive secondary metabolites that are derived from only a small fraction of the investigated halophilic actinomycetes, mainly from marine habitats, have revealed the huge capacity of this physiological group in production of new bioactive chemical entities. Combined high metabolic capacities of actinomycetes and unique features related to extremophilic nature of the halophilic actinomycetes have conferred on them an influential role for future biotechnological applications.     

Genetic and metabolic engineering of microorganisms for the development of new flavor compounds from terpenic substrates

Throughout human history, natural products have been the basis for the discovery and development of therapeutics, cosmetic and food compounds used in industry. Many compounds found in natural organisms are rather difficult to chemically synthesize and to extract in large amounts, and in this respect, genetic and metabolic engineering are playing an increasingly important role in the production of these compounds, such as new terpenes and terpenoids, which may potentially be used to create aromas in industry. Terpenes belong to the largest class of natural compounds, are produced by all living organisms and play a fundamental role in human nutrition, cosmetics and medicine. Recent advances in systems biology and synthetic biology are allowing us to perform metabolic engineering at the whole-cell level, thus enabling the optimal design of microorganisms for the efficient production of drugs, cosmetic and food additives. This review describes the recent advances made in the genetic and metabolic engineering of the terpenes pathway with a particular focus on systems biotechnology.     

Improvement of hairy root cultures and plants by changing biosynthetic pathways leading to pharmaceutical metabolites: Strategies and applications

A plethora of bioactive plant metabolites has been explored for pharmaceutical, food chemistry and agricultural applications. The chemical synthesis of these structures is often difficult, so plants are favorably used as producers. While whole plants can serve as a source for secondary metabolites and can be also improved by metabolic engineering, more often cell or organ cultures of relevant plant species are of interest. It should be noted that only in few cases the production for commercial application in such cultures has been achieved. Their genetic manipulation is sometimes faster and the production of a specific metabolite is more reliable, because of less environmental influences. In addition, upscaling in bioreactors is nowadays possible for many of these cultures, so some are already used in industry. There are approaches to alter the profile of metabolites not only by using plant genes, but also by using bacterial genes encoding modifying enzymes. Also, strategies to cope with unwanted or even toxic compounds are available. The need for metabolic engineering of plant secondary metabolite pathways is increasing with the rising demand for (novel) compounds with new bioactive properties. Here, we give some examples of recent developments for the metabolic engineering of plants and organ cultures, which can be used in the production of metabolites with interesting properties.     

Current status, strategies, and potential for the metabolic engineering of heterologous polyketides in Escherichia coli

Heterologous natural product biosynthesis has emerged as a strategy to produce medicinal compounds that pose challenges to conventional production routes. Polyketide compounds, an important class of natural products with wide-ranging therapeutic value, have been heterologously produced through Escherichia coli, presenting new opportunities to realize the medicinal potential of polyketide natural products. However, current production levels are often suboptimal when compared to native strain producers or heterologous theoretical yields. This problem provides an excellent opportunity to apply and further develop current metabolic engineering tools.     

Some results and prospects of studies in the area of marine biochemistry and biotechnology]

Recent studies on bioactive metabolites from marine macro- and microorganisms are reviewed with 83 refs. Structures of new sulphated and glycosylated secondary metabolites, which have been reported to have antifungal, immunomodulatory, and cytotoxic properties, are given. Some peculiarities of biosynthesis of natural compounds in marine organisms are revealed. It was shown that some natural products, isolated earlier from sponges, are produced by microbial symbionts. Different physiological activities associated with 8000 marine microbial (mainly symbiotic) strains are discussed as well as some prospects of marine biochemistry and biotechnology development.     

Advances in genetic engineering of marine algae

Algae are a component of bait sources for animal aquaculture, and they produce abundant valuable compounds for the chemical industry and human health. With today's fast growing demand for algae biofuels and the profitable market for cosmetics and pharmaceuticals made from algal natural products, the genetic engineering of marine algae has been attracting increasing attention as a crucial systemic technology to address the challenge of the biomass feedstock supply for sustainable industrial applications and to modify the metabolic pathway for the more efficient production of high-value products. Nevertheless, to date, only a few marine algae species can be genetically manipulated. In this article, an updated account of the research progress in marine algal genomics is presented along with methods for transformation. In addition, vector construction and gene selection strategies are reviewed. Meanwhile, a review on the progress of bioreactor technologies for marine algae culture is also revisited.     

Photoprotective compounds from marine organisms

The substantial loss in the stratospheric ozone layer and consequent increase in solar ultraviolet radiation on the earth’s surface have augmented the interest in searching for natural photoprotective compounds in organisms of marine as well as freshwater ecosystems. A number of photoprotective compounds such as mycosporine-like amino acids (MAAs), scytonemin, carotenoids and several other UV-absorbing substances of unknown chemical structure have been identified from different organisms. MAAs form the most common class of UV-absorbing compounds known to occur widely in various marine organisms; however, several compounds having UV-screening properties still need to be identified. The synthesis of scytonemin, a predominant UV-A-photoprotective pigment, is exclusively reported in cyanobacteria. Carotenoids are important components of the photosynthetic apparatus that serve both light-harvesting and photoprotective functions, either by direct quenching of the singlet oxygen or other toxic reactive oxygen species or by dissipating the excess energy in the photosynthetic apparatus. The production of photoprotective compounds is affected by several environmental factors such as different wavelengths of UVR, desiccation, nutrients, salt concentration, light as well as dark period, and still there is controversy about the biosynthesis of various photoprotective compounds. Recent studies have focused on marine organisms as a source of natural bioactive molecules having a photoprotective role, their biosynthesis and commercial application. However, there is a need for extensive work to explore the photoprotective role of various UV-absorbing compounds from marine habitats so that a range of biotechnological and pharmaceutical applications can be found.     

Positioning Bacillus subtilis as terpenoid cell factory

Increasing demands for bioactive compounds have motivated researchers to employ micro-organisms to produce complex natural products. Currently, Bacillus subtilis has been attracting lots of attention to be developed into terpenoids cell factories due to its generally recognized safe status and high isoprene precursor biosynthesis capacity by endogenous methylerythritol phosphate (MEP) pathway. In this review, we describe the up-to-date knowledge of each enzyme in MEP pathway and the subsequent steps of isomerization and condensation of C5 isoprene precursors. In addition, several representative terpene synthases expressed in B. subtilis and the engineering steps to improve corresponding terpenoids production are systematically discussed. Furthermore, the current available genetic tools are mentioned as along with promising strategies to improve terpenoids in B. subtilis, hoping to inspire future directions in metabolic engineering of B. subtilis for further terpenoid cell factory development.     

Marine drugs--macrolactins

The increasing demands for new lead compounds in pharmaceutical and agrochemical industries have driven scientists to search for new bioactive natural products. Marine microorganisms are rich sources of novel, bioactive secondary metabolites, and have attracted much attention of chemists, pharmacologists, and molecular biologists. This mini-review mainly focuses on macrolactins, a group of 24-membered lactone marine natural products, aiming at giving an overview on their sources, structures, biological activities, as well as their potential medical applications.     

天然活性先导化合物生物转化研究进展

天然活性先导化合物生物转化是利用生物催化剂(如：酶、微生物、动植物细胞)将加入到生物反应系统中的天然活性先导化合物进行特异性的分子结构修饰以获得高效、低毒新化合物的方法。该方法可以有效地提高已知的天然活性先导化合物的活性、降低毒副作用、改善水溶性和生物利用度,也可以用来生产具有重要应用价值的微量天然活性先导化合物,同时可用于药物代谢机制的研究。国内外学者已经针对甾体、醌类、黄酮类、萜类等化合物开展了天然活性先导化合物生物转化研究,筛选出一批有重要应用价值的生物转化反应类型,但针对天然活性先导化合物生物转化的机制、生物转化过程工程以及生物转化产物活性等方面的研究较少。将现代生命科学技术(如：生物催化剂的定向改造、高通量筛选、组合生物转化、非水相生物转化)引入天然活性先导化合物生物转化研究中,必将推进天然活性先导化合物的快速发展。     

Synthetic biology and metabolic engineering of actinomycetes for natural product discovery

Actinomycetes are one of the most valuable sources of natural products with industrial and medicinal importance. After more than half a century of exploitation, it has become increasingly challenging to find novel natural products with useful properties as the same known compounds are often repeatedly re-discovered when using traditional approaches. Modern genome mining approaches have led to the discovery of new biosynthetic gene clusters, thus indicating that actinomycetes still harbor a huge unexploited potential to produce novel natural products. In recent years, innovative synthetic biology and metabolic engineering tools have greatly accelerated the discovery of new natural products and the engineering of actinomycetes. In the first part of this review, we outline the successful application of metabolic engineering to optimize natural product production, focusing on the use of multi-omics data, genome-scale metabolic models, rational approaches to balance precursor pools, and the engineering of regulatory genes and regulatory elements. In the second part, we summarize the recent advances of synthetic biology for actinomycetal metabolic engineering including cluster assembly, cloning and expression, CRISPR/Cas9 technologies, and chassis strain development for natural product overproduction and discovery. Finally, we describe new advances in reprogramming biosynthetic pathways through polyketide synthase and non-ribosomal peptide synthetase engineering. These new developments are expected to revitalize discovery and development of new natural products with medicinal and other industrial applications.     

Bioactive Peptides from Marine Ascidians and Future Drug Development–A Review

Marine ascidians are considered as one of the richest sources of bioactive compounds. The extraction and utilization of marine peptides have been attracted much attention owing to their potential health benefits. Most of the bioactive compounds from marine ascidians are already in different phases of the clinical and preclinical pipeline. They can be used in different functional and nutraceutical values due to their antineoplastic, antihypertensive, antioxidant, and antimicrobial properties. The screening in vivo and in vitro bioassays are coupled to the purification process for the exploration of its biological interest which is of great value. The growing significance to study marine natural products results from the discovery of novel pharmacological tools including potent anticancer drugs and other drugs are in clinical/pre-clinical trials. The present review highlights the recent research progress in marine ascidians’ peptides and its prospects for the future pharmaceutical development.     

Recent advances in natural products exploitation in Streptomyces via synthetic biology

Natural products of microbial origin have proven to be the wellspring of clinically useful compounds for human therapeutics. Streptomyces species are predominant sources of bioactive compounds, most of which serve as potential drug candidates. While the exploitation of natural products has been severely reduced over the past two decades, the growing crisis of evolution and dissemination of drug resistant pathogens have again attracted great interest in this field. The emerging synthetic biology has been heralded as a new bioengineering platform to discover novel bioactive compounds and expand bioactive natural products diversity and production. Herein, we review recent advances in the natural products exploitation of Streptomyces with the applications of synthetic biology from three major aspects, including recently developed synthetic biology tools, natural products biosynthetic pathway engineering strategies as well as chassis host modifications.