Commercial opportunities for pesticides based on plant essential oils in agriculture, industry and consumer products

In spite of intensive research on plant natural products and insect-plant chemical interactions over the past three decades, only two new types of botanical insecticides have been commercialized with any success in the past 15 years, those based on neem seed extracts (azadirachtin), and those based on plant essential oils. Certain plant essential oils, obtained through steam distillation and rich in mono- and sesquiterpenes and related phenols, are widely used in the flavouring and fragrance industries and in aromatherapy. Some aromatic plants have traditionally been used for stored product protection, but the potential for development of pesticides from plant essential oils for use in a wide range of pest management applications has only recently been realized. Many plant essential oils and their major terpenoid constituents are neurotoxic to insects and mites and behaviourally active at sublethal concentrations. Most plant essential oils are complex mixtures. In our laboratory we have demonstrated that individual constituents of oils rarely account for a major share of the respective oil’s toxicity. Further, our results suggest synergy among constituents, including among those that appear non-toxic in isolation. Repellent effects may be particularly useful in applications against public health and domestic pests, but may be useful in specific agricultural applications as well. In all of these applications, there is a premium on human and animal safety that takes priority over absolute efficacy. In agriculture, the main market niche for essential oil-based pesticides is in organic food production, at least in developed countries, where there are fewer competing pest management products. There is also scope for mixing these oils with conventional insecticides and for enhancing their efficacy with natural synergists. Some examples of field efficacy against agricultural pests are discussed.     

High-value oils from plants

The seed oils of domesticated oilseed crops are major agricultural commodities that are used primarily for nutritional applications, but in recent years there has been increasing use of these oils for production of biofuels and chemical feedstocks. This is being driven in part by the rapidly rising costs of petroleum, increased concern about the environmental impact of using fossil oil, and the need to develop renewable domestic sources of fuel and industrial raw materials. There is also a need to develop sustainable sources of nutritionally important fatty acids such as those that are typically derived from fish oil. Plant oils can provide renewable sources of high-value fatty acids for both the chemical and health-related industries. The value and application of an oil are determined largely by its fatty acid composition, and while most vegetable oils contain just five basic fatty acid structures, there is a rich diversity of fatty acids present in nature, many of which have potential usage in industry. In this review, we describe several areas where plant oils can have a significant impact on the emerging bioeconomy and the types of fatty acids that are required in these various applications. We also outline the current understanding of the underlying biochemical and molecular mechanisms of seed oil production, and the challenges and potential in translating this knowledge into the rational design and engineering of crop plants to produce high-value oils in plant seeds.     

Production and engineering of terpenoids in plant cell culture

Terpenoids are a diverse class of natural products that have many functions in the plant kingdom and in human health and nutrition. Their chemical diversity has led to the discovery of over 40,000 different structures, with several classes serving as important pharmaceutical agents, including the anticancer agents paclitaxel (Taxol) and terpenoid-derived indole alkaloids. Many terpenoid compounds are found in low yield from natural sources, so plant cell cultures have been investigated as an alternate production strategy. Metabolic engineering of whole plants and plant cell cultures is an effective tool to both increase terpenoid yield and alter terpenoid distribution for desired properties such as enhanced flavor, fragrance or color. Recent advances in defining terpenoid metabolic pathways, particularly in secondary metabolism, enhanced knowledge concerning regulation of terpenoid accumulation, and application of emerging plant systems biology approaches, have enabled metabolic engineering of terpenoid production. This paper reviews the current state of knowledge of terpenoid metabolism, with a special focus on production of important pharmaceutically active secondary metabolic terpenoids in plant cell cultures. Strategies for defining pathways and uncovering rate-influencing steps in global metabolism, and applying this information for successful terpenoid metabolic engineering, are emphasized.     

Bioplastik aus Nutzpflanzen: Palette der nachwachsenden Rohstoffe erweitert

Crop plants are ultivated for producing starch, oils, proteins, sugar, fibres and other products. An increasing amount of these products is used as renewable resources for industrial purposes. But there is still a demand for new products with improved properties such as biodegradable plastics like polyhydroxyfatty acids (PHF) which cannot be found in the plant kingdom. PHF are linear polymers found as a major storage component in many bacterial species. Polyhydroxy‐butyric acid, poly(3HB), is the most abundant representative of this class of polymers. Three enzymes have been identified from the bacterium Ralstonia eutropha responsible for poly(3HB)‐synthesis. These enzymes are encoded by three different genes. PHF can be utilized by many microorganisms as carbon‐ and energy‐source with the help of certain depo lymerases. PHF‐storing plants fulfill the criteria as renewable resource for biodegradable plastics. Using Arabidopsis thaliana as a model plant, the poly(3HB)‐metabolism has been established in plants after transformation with the three bacterial genes under the control of plant promotors. Transgenic plants have been selected accumulating up to 40% poly(3HB) dry weight. Recent data demonstrate that high amounts of poly(3HB) can also be stored in rape seed, the main oil producing rop for moderate limates. This offers the possibility to breed poly(3HB)‐producing rop plants with full agronomical performance.     

Biostimulants enhance growth and drought tolerance in Arabidopsis thaliana and exhibit chemical priming action

The usage of biostimulants in agriculture has been steadily increasing in recent years, and their benefits have been recognised by growers. The growing interest from industry has led to a boom in the number of products on the market, many of which are derived from a diverse range of sources such as microbials, plant extracts, hydrolysed amino acids and algal extracts. However, there has been a slower recognition of the biostimulant sector by the scientific community. This has been a result of limited fundamental research into the modes of action of many biostimulant products and the speed at which new multi‐compound products have entered the market. In this study, we have developed a readily reproducible bioassay using the model plant Arabidopsis thaliana to test biostimulant efficacy under drought conditions and assess any chemical priming action. We have screened three products with biostimulant action derived from amino acids (Delfan Plus), Ascophyllum nodosum extract (Phylgreen) or potassium phosphite (Trafos K). Under a progressive soil drought condition, we measured changes in plant growth, biochemical content and gene expression levels. Our results demonstrated biostimulant‐mediated drought tolerance, with the products requiring different application timings for successful stress mitigation. The analysis of the biochemical and gene expression changes provided evidence of chemical priming action when plants were pre‐treated with biostimulants prior to the drought stress exposure.     

Process strategies for plant cell cultures

Plants synthesize a tremendously wide range of chemical structures, many of which have been used over the centuries to the benefit of mankind. Today, with attention again turning to the plant kingdom as a source of drugs, food additives, perfumes and so on, a further dimension has been added to traditional methods of synthesis of these products: the use of cultured plant cells. Although plant cell culture technology is perhaps still in its infancy compared with other aspects of biotechnology, an extensive information and experience base is being established for the development of plant cell processes. The establishment of such a foundation is important for the application of plant cell technology in the years ahead.     

Interspecific hybridization in plant-associated fungi and oomycetes: a review

Fungi (kingdom Mycota) and oomycetes (kingdom Stramenopila, phylum Oomycota) are crucially important in the nutrient cycles of the world. Their interactions with plants sometimes benefit and sometimes act to the detriment of humans. Many fungi establish ecologically vital mutualisms, such as in mycorrhizal fungi that enhance nutrient acquisition, and endophytes that combat insects and other herbivores. Other fungi and many oomycetes are plant pathogens that devastate natural and agricultural populations of plant species. Studies of fungal and oomycete evolution were extraordinarily difficult until the advent of molecular phylogenetics. Over the past decade, researchers applying these new tools to fungi and oomycetes have made astounding new discoveries, among which is the potential for interspecific hybridization. Consequences of hybridization among pathogens include adaptation to new niches such as new host species, and increased or decreased virulence. Hybrid mutualists may also be better adapted to new hosts and can provide greater or more diverse benefits to host plants.     

Metabolic engineering of fatty acid biosynthesis in plants.

Fatty acids are the most abundant form of reduced carbon chains available from nature and have diverse uses ranging from food to industrial feedstocks. Plants represent a significant renewable source of fatty acids because many species accumulate them in the form of triacylglycerol as major storage components in seeds. With the advent of plant transformation technology, metabolic engineering of oilseed fatty acids has become possible and transgenic plant oils represent some of the first successes in design of modified plant products. Directed gene down-regulation strategies have enabled the specific tailoring of common fatty acids in several oilseed crops. In addition, transfer of novel fatty acid biosynthetic genes from noncommercial plants has allowed the production of novel oil compositions in oilseed crops. These and future endeavors aim to produce seeds higher in oil content as well as new oils that are more stable, are healthier for humans, and can serve as a renewable source of industrial commodities. Large-scale new industrial uses of engineered plant oils are on the horizon but will require a better understanding of factors that limit the accumulation of unusual fatty acid structures in seeds.     

植物精油生物活性作用机理研究进展

植物精油具有多种生物活性,被广泛应用于医疗保健、食品工业、化妆品、农业等多个领域.本文综述植物精油抗菌、抗癌、抑制肿瘤细胞生长、抗氧化、延缓衰老、防治心血管疾病、抗病毒、消炎等多种生物活性的作用机理,并展望植物精油今后研究的重点及突破方向.     

Microbial biosurfactants: current trends and applications in agricultural and biomedical industries

Synthetic surfactants are becoming increasingly unpopular in many applications due to previously disregarded effects on biological systems and this has led to a new focus on replacing such products with biosurfactants that are biodegradable and produced from renewal resources. Microbially derived biosurfactants have been investigated in numerous studies in areas including: increasing feed digestibility in an agricultural context, improving seed protection and fertility, plant pathogen control, antimicrobial activity, antibiofilm activity, wound healing and dermatological care, improved oral cavity care, drug delivery systems and anticancer treatments. The development of the potential of biosurfactants has been hindered somewhat by the myriad of approaches taken in their investigations, the focus on pathogens as source species and the costs associated with large-scale production. Here, we focus on various microbial sources of biosurfactants and the current trends in terms of agricultural and biomedical applications.     

Laurie oil resources

Lauric oils and their derivatives have many applications both in the food and chemical industries. The major sources and some alternative raw materials for this multi-billon dollar business are discussed in the light of their ability to supply future market needs. There should be ample supply of lauric oils—except when drought and possibly disease affect large areas of coconut plantations—because of the rapid increase in palm kernel oil production expected from the African oil palm during the next decade. Most other sources are unlikely to be important in the short term because of the generally adequate supply of lauric oils and the considerable amount of research still needed to convert the best options into viable crops. However, a dramatic effect on supply can be expected if it becomes possible to manipulate the appropriate genes from lauric oil producing species of Cuphea into a conventional oil crop like rape. Future demand for lauric oils will be affected by the relative price of other vegetable oils and petroleum feedstocks that can be used to replace them in the manufacture of an increasing number of end products in both the food and chemical industries.     

植物精油化学成分及其抗菌活性的研究进展

植物精油是一类从植物中萃取的芳香味油状液体,是一类优良的天然抗菌材料。作为抗菌材料,植物精油具有以下优点:具有广谱高效的抗菌活性;具有熏蒸特性、气味芳香;取自天然植物,绿色环保;来源广,提取容易。植物精油因其多种优点,在抗菌领域具有巨大的潜在应用价值。本文从植物精油的分布及化学成分、抗细菌活性和抗真菌活性的研究,以及植物精油化学成分与抗菌活性之间的联系等方面对植物精油的抗菌性能进行评述,以期促进植物精油在抗菌领域的广泛应用,同时给从事植物精油抗菌研究的科研工作者提供参考。     

Plant biodiversity: phytochemicals and health

Biodiversity may be defined as the variability occuring among living organisms and affecting all species of animals and plants, their genetics and their environment. Biological diversity of plants also relies on the chemical diversity deriving from their specialized metabolites which possess a wide range of different chemical structures as a result of plant evolution. They are responsible for the plant ecological properties and are required for the plant-environment interactions. In addition, many of them display important pharmacological properties. In the recent years, the growing interest in using plant metabolites to treat diseases in humans and animals and the high request of health products originating from natural sources rather than synthetic has revived the research on plant biodiversity to identify new bioactive molecules. Based on our studies on the chemical and biological characterization of rare or less studied plant species, the present paper aims to describe a selection of botanical species with phytopharmaceutical importance in order to highlight the chemical polymorphism deriving from their biodiversity along with its implications on bioactivity.     

Antimicrobial peptides and plant disease control

Several diseases caused by viruses, bacteria and fungi affect plant crops, resulting in losses and decreasing the quality and safety of agricultural products. Plant disease control relies mainly on chemical pesticides that are currently subject to strong restrictions and regulatory requirements. Antimicrobial peptides are interesting compounds in plant health because there is a need for new products in plant protection that fit into the new regulations. Living organisms secrete a wide range of antimicrobial peptides produced through ribosomal (defensins and small bacteriocins) or non-ribosomal synthesis (peptaibols, cyclopeptides and pseudopeptides). Several antimicrobial peptides are the basis for the design of new synthetic analogues, have been expressed in transgenic plants to confer disease protection or are secreted by microorganisms that are active ingredients of commercial biopesticides.     

Le risorse genetiche vegetali. I. Principi,realtà, problemi

Abstract

Plant genetic resources. I. The problem of the conservation of plant genetic resources emerges from the examination of the consequences of the genetic erosion and of the destruction of genetic variability, which provoke decline and disappearance of plant species, of agricultural value too.

Information are given on species and primitive or local varieties desappeared or threatened by destruction, on the emergency situation already existing in various areas, including also centres of origin and diversification, and on the risks of a plant breeding work manipulating a reduced genetic basis.

Thus, it is crucial to collect and maintain an abundant germplasm of the main crops, as well as of those species of minor agricultural importance. It is wise also to pay attention to plant species of potential value as new food crops or as sources for industrial pharmaceutical or pesticide products or other products with specific chemical properties.

Finally, the author underlines the urgent need, for the future progress of agriculture and for the benefit of the mankind, to safeguard plant genetic resources, which must be considered as essential part of the problem of the conservation of the nature and of its resources.     

Growth and polyhydroxybutyrate production by Ralstonia eutropha in emulsified plant oil medium

Polyhydroxyalkanoates (PHAs) are natural polyesters synthesized by bacteria for carbon and energy storage that also have commercial potential as bioplastics. One promising class of carbon feedstocks for industrial PHA production is plant oils, due to the high carbon content of these compounds. The bacterium Ralstonia eutropha accumulates high levels of PHA and can effectively utilize plant oil. Growth experiments that include plant oil, however, are difficult to conduct in a quantitative and reproducible manner due to the heterogeneity of the two-phase medium. In order to overcome this obstacle, a new culture method was developed in which palm oil was emulsified in growth medium using the glycoprotein gum arabic as the emulsifying agent. Gum arabic did not influence R. eutropha growth and could not be used as a nutrient source by the bacteria. R. eutropha was grown in the emulsified oil medium and PHA production was measured over time. Additionally, an extraction method was developed to monitor oil consumption. The new method described in this study allows quantitative, reproducible R. eutropha experiments to be performed with plant oils. The method may also prove useful for studying growth of different bacteria on plant oils and other hydrophobic carbon sources.     

From flavors and pharmaceuticals to advanced biofuels: Production of isoprenoids in Saccharomyces cerevisiae

Isoprenoids denote the largest group of chemicals in the plant kingdom and are employed for a wide range of applications in the food and pharmaceutical industry. In recent years, isoprenoids have additionally been recognized as suitable replacements for petroleum-derived fuels and could thus promote the transition towards a more sustainable society. To realize the biofuel potential of isoprenoids, a very efficient production system is required. While complex chemical structures as well as the low abundance in nature demonstrate the shortcomings of chemical synthesis and plant extraction, isoprenoids can be produced by genetically engineered microorganisms from renewable carbon sources. In this article, we summarize the development of isoprenoid applications from flavors and pharmaceuticals to advanced biofuels and review the strategies to design microbial cell factories, focusing on Saccharomyces cerevisiae for the production of these compounds. While the high complexity of biosynthetic pathways and the toxicity of certain isoprenoids still denote challenges that need to be addressed, metabolic engineering has enabled large-scale production of several terpenoids and thus, the utilization of these compounds is likely to expand in the future.