Insect-symbiont systems: From complex relationships to biotechnological applications

Microbial symbiosis is a ubiquitous aspect of life and was a major element in the ability of insects to explore several adverse environments. To date, the study of symbiosis in insects has been impaired by the unculturability of most symbionts. However, some molecular methods represent powerful tools to help understand insect-microorganism associations and to disclose new symbiont-host systems. Beyond playing an essential role in nutrition and development of the insects, symbionts can produce bioactive compounds that protect the host against adverse environmental conditions, predators and/or direct competitors. Since the search for natural bioactive products and new enzymes is a developing area, understanding the diversity and nature of symbiont-host relationships paves the way for the exploitation of new resources in biotechnology. Furthermore, genetic transformation of the symbionts with genes that code for compounds that are toxic for pathogenic and phytopathogenic agents is also a promising area of application of the insect-symbiont relationships. The search for new bioactive compounds, the use of symbionts for pest and disease control and the molecular strategies applied for these purposes are issues of particular interest for innovative biotechnological applications and are addressed in the present review.     

Plant protoplasts: status and biotechnological perspectives

Plant protoplasts ("naked" cells) provide a unique single cell system to underpin several aspects of modern biotechnology. Major advances in genomics, proteomics, and metabolomics have stimulated renewed interest in these osmotically fragile wall-less cells. Reliable procedures are available to isolate and culture protoplasts from a range of plants, including both monocotyledonous and dicotyledonous crops. Several parameters, particularly the source tissue, culture medium, and environmental factors, influence the ability of protoplasts and protoplast-derived cells to express their totipotency and to develop into fertile plants. Importantly, novel approaches to maximise the efficiency of protoplast-to-plant systems include techniques already well established for animal and microbial cells, such as electrostimulation and exposure of protoplasts to surfactants and respiratory gas carriers, especially perfluorochemicals and hemoglobin. However, despite at least four decades of concerted effort and technology transfer between laboratories worldwide, many species still remain recalcitrant in culture. Nevertheless, isolated protoplasts are unique to a range of experimental procedures. In the context of plant genetic manipulation, somatic hybridisation by protoplast fusion enables nuclear and cytoplasmic genomes to be combined, fully or partially, at the interspecific and intergeneric levels to circumvent naturally occurring sexual incompatibility barriers. Uptake of isolated DNA into protoplasts provides the basis for transient and stable nuclear transformation, and also organelle transformation to generate transplastomic plants. Isolated protoplasts are also exploited in numerous miscellaneous studies involving membrane function, cell structure, synthesis of pharmaceutical products, and toxicological assessments. This review focuses upon the most recent developments in protoplast-based technologies.     

Mosquito behavioural aspects of vector-human interactions in the Anopheles gambiae complex

The behaviour of two of the most anthropophilic malaria vectors in the world, Anopheles gambiae Giles and An. arabiensis Patton, is revisited with respect to recent studies on their host preferences and the chemical ecology of host-seeking. Issues are discussed in relation to the ways anthropophily may have arisen in the complex, and the opportunities the study of olfaction and host-seeking behaviour offers to malaria control in Africa.     

Mineral-microbe interactions: biotechnological potential of bioweathering

Mineral-microbe interaction has been a key factor shaping the lithosphere of our planet since the Precambrian. Detailed investigation has been mainly focused on the role of bioweathering in biomining processes, leading to the selection of highly efficient microbial inoculants for the recovery of metals. Here we expand this scenario, presenting additional applications of bacteria and fungi in mineral dissolution, a process with novel biotechnological potential that has been poorly investigated. The ability of microorganisms to trigger soil formation and to sustain plant establishment and growth are suggested as invaluable tools to counteract the expansion of arid lands and to increase crop productivity. Furthermore, interesting exploitations of mineral weathering microbes are represented by biorestoration and bioremediation technologies, innovative and competitive solutions characterized by economical and environmental advantages. Overall, in the future the study and application of the metabolic properties of microbial communities capable of weathering can represent a driving force in the expanding sector of environmental biotechnology.     

3-Hydroxypropionaldehyde: applications and perspectives of biotechnological production

3-Hydroxypropionaldehyde (3-HPA) forms, together with HPA-hydrate and HPA-dimer, a dynamic, multi-component system (HPA system) used in food preservation, as a precursor for many modern chemicals such as acrolein, acrylic acid, and 1,3-propanediol (1,3-PDO), and for polymer production. 3-HPA can be obtained both through traditional chemistry and bacterial fermentation. To date, 3-HPA has been produced from petrochemical resources as an intermediate in 1,3-PDO production. In vivo, glycerol is converted in one enzymatic step into 3-HPA. The 3-HPA-producing Lactobacillus reuteri is used as a probiotic in the health care of humans and animals. The biotechnological production of 3-HPA from renewable resources is desirable both for use of 3-HPA in foods and for the production of bulk chemicals. The main challenge will be the efficient production and recovery of pure 3-HPA.     

Seaweed protoplasts: status,biotechnological perspectives and needs

Protoplasts are living plant cells without cell walls which offer a unique uniform single cell system that facilitates several aspects of modern biotechnology, including genetic transformation and metabolic engineering. Extraction of cell wall lytic enzymes from different phycophages and microbial sources has greatly improved protoplast isolation and their yield from a number of anatomically more complex species of brown and red seaweeds which earlier remained recalcitrant. Recently, recombinant cell wall lytic enzymes were also produced and evaluated with native ones for their potential abilities in producing viable protoplasts from Laminaria. Reliable procedures are now available to isolate and culture protoplasts from diverse groups of seaweeds. To date, there are 89 species belonging to 36 genera of green, red and brown seaweeds from which successful protoplast isolation and regeneration has been reported. Of the total species studied for protoplasts, most belonged to Rhodophyta with 41 species (13 genera) followed by Chlorophyta and Phaeophyta with 24 species each belonging to 5 and 18 genera, respectively. Regeneration of protoplast-to-plant system is available for a large number of species, with extensive literature relating to their culture methods and morphogenesis. In the context of plant genetic manipulation, somatic hybridization by protoplast fusion has been accomplished in a number of economically important species with various levels of success. Protoplasts have also been used for studying foreign gene expression in Porphyra and Ulva. Isolated protoplasts are also exploited in numerous miscellaneous studies involving membrane function, cell structure, bio-chemical synthesis of cell walls etc. This article briefly reviews the status of various developments in seaweed protoplasts research and their potentials in genetic improvement of seaweeds, along with needs that must to be fulfilled for effective realization of the objectives envisaged for protoplast research.     

Aminomutases: mechanistic diversity, biotechnological applications and future perspectives

Aminomutases carry out the chemically challenging exchange of a hydrogen atom and an amine substituent present on neighboring carbon atoms. In recent years, aminomutases have been intensively investigated for their biophysical, structural and mechanistic characteristics. The reactions catalyzed by these enzymes have considerable potential for biotechnological applications. Here, we present an overview of this diverse group of enzymes, with a focus on enzymatic mechanisms and recent developments in their use in applied biocatalysis.     

History of protein-protein interactions: from egg-white to complex networks

Today, it is widely appreciated that protein-protein interactions play a fundamental role in biological processes. This was not always the case. The study of protein interactions started slowly and evolved considerably, together with conceptual and technological progress in different areas of research through the late 19th and the 20th centuries. In this review, we present some of the key experiments that have introduced major conceptual advances in biochemistry and molecular biology, and review technological breakthroughs that have paved the way for today's systems-wide approaches to protein-protein interaction analysis.     

Bacterial outer membrane proteins: topological analyses and biotechnological perspectives

The outer membrane proteins (OMPs) from gram-negative bacteria form a distinct group of integral membrane proteins with unusual primary, secondary and tertiary structures. Unlike typical prokaryotic and eukaryotic membrane proteins, bacterial OMPs contain primarily polar sequences, arranged in amphipathic antiparallel beta-barrels, and inclined to the plane of the membrane. Due to their unique structure, OMPs have recently become the subject of extensive study. This article reviews (i) experimental and theoretical approaches of topological analyses used in the study of OMPs, and (ii) the applications of OMPs.     

Feruloyl Esterases as Biotechnological Tools： Current and Future Perspectives

Feruloyl esterases represent a diverse group of hydrolases catalyzing the cleavage and formation of ester bonds between plant cell wall polysaccharide and phenolic acid. They are widely distributed in plants and microorganisms. Besides lipases, a considerable number of microbial feruloyl esterases have also been discovered and overexpressed. This review summarizes the latest research on their classification, production, and biophysicochemical properties. Special emphasis is given to the importance of that type of enzyme and their related phenolic ferulic acid compound in biotechnological processes, and industrial and medicinal applications.     

Biosynthesis and biotechnological production of flavanones: current state and perspectives

Polyphenols produced in a wide variety of flowering and fruit-bearing plants have the potential to be valuable fine chemicals for the treatment of an assortment of human maladies. One of the major constituents within this chemical class are flavonoids, among which flavanones, as the precursor to all flavonoid structures, are the most prevalent. We review the current status of flavanone production technology using microorganisms, with focus on heterologous protein expression. Such processes appear as attractive production alternatives for commercial synthesis of these high-value chemicals as traditional chemical, and plant cell cultures have significant drawbacks. Other issues of importance, including fermentation configurations and economics, are also considered.     

The seaweed holobiont: from microecology to biotechnological applications

In the ocean, seaweed and microorganisms have coexisted since the earliest stages of evolution and formed an inextricable relationship. Recently, seaweed has attracted extensive attention worldwide for ecological and industrial purposes, but the function of its closely related microbes is often ignored. Microbes play an indispensable role in different stages of seaweed growth, development and maturity. A very diverse group of seaweed-associated microbes have important functions and are dynamically reconstructed as the marine environment fluctuates, forming an inseparable ‘holobiont’ with their host. To further understand the function and significance of holobionts, this review first reports on recent advances in revealing seaweed-associated microbe spatial and temporal distribution. Then, this review discusses the microbe and seaweed interactions and their ecological significance, and summarizes the current applications of the seaweed–microbe relationship in various environmental and biological technologies. Sustainable industries based on seaweed holobionts could become an integral part of the future bioeconomy because they can provide more resource-efficient food, high-value chemicals and medical materials. Moreover, holobionts may provide a new approach to marine environment restoration.     

RNase P: from biological function to biotechnological applications

The M1 RNA subunit of Escherichia coli RNase P is a ribozyme responsible for the catalytic activity of the complex. It removes the 5' leader sequence from tRNA precursors to form mature tRNAs. M1 recognizes its target mainly on the basis of its structure and this allows the design of modified ribozymes engineered to destroy other molecules without the need for special sequences in the targeted mRNAs. M1 is thus an ideal tool to eliminate the tumourigenic chimeric messengers created after chromosomal translocations. These results have direct implications for cancer therapeutics and molecular biology in general.     

Advances in bacterial exopolysaccharides: from production to biotechnological applications

A vast number of bacterial extracellular polysaccharides (EPSs) have been reported over recent decades, and their composition, structure, biosynthesis and functional properties have been extensively studied. Despite the great diversity of molecular structures already described for bacterial EPSs, only a few have been industrially developed. The main constraints to full commercialization are their production costs, mostly related to substrate cost and downstream processing. In this article, we review EPS biosynthetic and fermentative processes, along with current downstream strategies. Limitations and constraints of bacterial EPS development are stressed and correlation of bacterial EPS properties with polymer applications is emphasized.     

Flue gas compounds and microalgae: (Bio-)chemical interactions leading to biotechnological opportunities

Flue gases are a resource yet to be fully utilised in microalgal biotechnology, not only to moderate the anthropogenic effects on our climate, but also to steer microalgal resource management towards innovative applications of microalgal biomass compounds. These gases, both untreated and treated into current discharge standards, contain CO₂, N₂, H₂O, O₂, NO_x, SO_x, C_xH_y, CO, particulate matter, halogen acids and heavy metals. To better steer and engineer flue gas-fed microalgal cultures, all these compounds need to be considered. Therefore, here, we review (i) the chemical composition and treatment technologies of flue gas, (ii) the uptake pathways and removal of the different compounds in microalgae reactors, and (iii) the tolerance and effects on microalgae of all flue gas compounds. By emphasising the interactions between microalgae and flue gas compounds, we envisage new pathways for microalgal biomass valorisation such as enzyme production for environmental technology, novel biogas production and biosequestration of minerals. Furthermore, we highlight fundamental and applied research niches that merit further investigation.     

Burkholderia cepacia complex species: health hazards and biotechnological potential

The Burkholderia cepacia complex is a group of nine closely related bacterial species that have useful properties in the natural environment as plant pest antagonists, plant growth promoters and degradative agents of toxic substances. Because these species are human opportunistic pathogens, especially in cystic fibrosis patients, biotechnological applications that involve environmental releases have been severely restricted. Recent progress in understanding the taxonomy, epidemiology and ecology of the B. cepacia complex species has unravelled considerable variability in their pathogenicity and ecological properties, which has set the basis for a reassessment of the risk posed by individual species to human health.     

Artemisinin: current state and perspectives for biotechnological production of an antimalarial drug

Artemisinin isolated from the aerial parts of Artemisia annua L. is a promising and potent antimalarial drug which has a remarkable activity against chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum, and is useful in treatment of cerebral malaria. Because the low content (0.01–1 %) of artemisinin in A. annua is a limitation to the commercial production of the drug, many research groups have been focusing their researches on enhancing the production of artemisinin in tissue culture or in the whole plant of A. annua. This review mainly focuses on the progresses made in the production of artemisinin from A. annua by biotechnological strategies including in vitro tissue culture, metabolic regulation of artemisinin biosynthesis, genetic engineering, and bioreactor technology.