Improvement of bacterial cellulose production in <Emphasis Type="Italic">Acetobacter xylinum</Emphasis> using byproduct produced by <Emphasis Type="Italic">Gluconacetobacter hansenii</Emphasis>

A single sugar α-linked glucuronic acid based oligosaccharide (SSGO) is water soluble oligosaccharides (WSOS) obtained by Gluconacetobacter hansenii PJK (KCTC 10505BP) as a byproduct during bacterial cellulose (BC) production. In this study, SSGO was used for the improvement of BC production by the vinegar bacterium, Acetobacter xylinum, which produces heteropolysaccharides as a byproduct. The addition of 1.0% SSGO to the chemically defined medium (CDM) resulted in an 89.3% increase in BC production by A. xylinum after 15 days of cultivation under static condition, and a 52.3% increase in BC production by G. hansenii. Both the dry cell weight and live cell density of A. xylinum increased 50% with the addition of 1.0% SSGO. SSGO successfully improved BC production by A. xylinum.     

Development of Cre-<Emphasis Type="Italic">lox</Emphasis> based multiple knockout system in <Emphasis Type="Italic">Deinococcus radiodurans</Emphasis> R1

The extremophilic bacterium Deinococcus radiodurans R1 has been considered as an attractive microorganism due to its remarkable tolerance to various external stresses. Considering the nature of D. radiodurans R1, it has potential as a platform microorganism for industrial applications, including biorefinery and bioremediation process. However, D. radiodurans R1 is well known for its hard genetic manipulation. Thus, much effort has been made to develop efficient genetic engineering tools for making D. radiodurans R1 suitable for industrial platform microorganism. Although a plasmid-based single gene knockout method has been reported, development of multiple gene knockout system has not yet been reported. Here we report, for the first time, Cre-lox based rapid and efficient multiple knockout method for metabolic engineering of D. radiodurans R1. Also, deletion of dr0053 gene was successfully achieved within seven days to make biofilm overproducing strain.     

Dynamic mechanical properties of bacterial cellulose nanofibres

In this work, dynamic mechanical properties of the grown bacterial cellulose (BC) nanofibers were investigated. BC pellicles were fabricated using bacterial fermentation (Gluconacetobacter xylinus). The morphology results confirmed that the dried BC at ambient conditions could be categorized as a xerogel. The thermal dynamic mechanical analysis results indicated that the bound water in bacterial cellulose structure had a very significant effect on thermal and dynamic mechanical properties of BC pellicles. The results of dehydration kinetics study showed that the main mechanism governing water loss of BC was Fickian diffusion. The glass transition temperatures (T_g) of the BC dried at 25 °C (ambient temperature) and 105 °C were estimated ??33 and ??18 °C, respectively. This discrepancy can be attributed to the plasticizing effect of the bound water of BC dried at ambient temperature. Furthermore, the results indicated that its modulus drop smaller than one order of magnitude can be attributed to its high crystalline nature. The storage modulus versus frequency increased due to the limitation of the relaxation process of the polymer chains. Moreover, the relaxation time distribution was achieved from the slope of the modulus master curve versus logarithmic frequency. As a result, BC exhibited a solid-like behavior.     

Recent advances for serial processes of hazardous chemicals in fully integrated microfluidic systems

The development and enlargement of toxic and hazardous chemicals are severely limited by health and safety concerns. We summarize studies on fully integrated micro-chemical systems and total processes to reduce accidental exposure to various regents that are toxic, explosive, or carcinogenic, which significantly improved the safety of work involving risky compounds. This review covers the leak-free continuous-flow processes of hazardous chemicals in fully integrated microfluidic systems, specially denoted as micro-total envelope systems (μ-TESs), that are conducting a serial process of the generation of hazardous reagents, in-situ purification and separation, subsequent reaction, and product isolation with improved efficiencies. These attempts suggest safe and efficient tools and processes of useful but hazardous chemicals for researchers and manufacturing workers in the field of pharmaceutic discovery, natural products, biology as well as materials synthesis.     

New methods for the one-pot processing of polysaccharide components (cellulose and hemicelluloses) of lignocellulose biomass into valuable products. Part 3: Products synthesized via the biotechnological conversion of poly- and monosaccharides of biomass

Part 3 of the review discusses the modern aspects in the biotechnological synthesis of the valuable chemicals derived from the lignocellulosic biomass, including ethanol, n-butanol, isobutanol, 2,3-butanediol, and lactic and succinic acids. A comparative characteristic of different approaches (including SHF, SSF, SSCF and CBP) toward biosynthesis of valuable products is given. It is shown that the consolidated processing of lignocellulose into the valuable chemicals is a promising approach toward their direct synthesis by fermentation, but remains less efficient than other processing methods. Development of genetic engineering tools and the application of synthetic biology will allow to develop more efficient strains and advanced biotechnological processes for lignocellulose processing.     

Engineering of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> for enhanced production of L-lactic acid by co-expression of acid-stable glycolytic enzymes from <Emphasis Type="Italic">Picrophilus torridus</Emphasis>

L-lactic acid, as a monomer of polylactic acid, has attracted much attention because of the growing market for biodegradable bioplastics to reduce landfill waste. As an industrial L-lactic acid producer, Saccharomyces cerevisiae is generally used because it survives in low pH. However, in S. cerevisiae, production of L-lactic acid causes a decrease in intracellular pH, which leads to slow glycolytic flux, and consequently results in a lower productivity of L-lactic acid. For this reason, yeast strains that maintain their growth and the activities of metabolic enzymes during lactic acid production need to be developed for industrial applications. Herein, acid stable enzymes from acidophilic archaea Picrophilus torridus were expressed in L-lactic acid producing S. cerevisiae to increase glycolytic flux at low intracellular pH conditions for a higher L-lactic acid titer. Enzymes of lower glycolysis including phosphoglycerate kinase, phosphoglycerate mutase, enolase, and pyruvate kinase from P. torridus were introduced to develop a novel L-lactic acid producing strain. It was clearly shown that the production of lactic acid in the developed strain increased by 20% compared to the parental strain. To the best of our knowledge, this is the first report of P. torridus enzymes used in metabolic engineering to enhance the metabolic flux at a lower intracellular pH. Moreover, it is expected that the new strain will have an enhanced glycolytic flux at a low pH expressing acid stable enzymes that could be used to produce other valuable organic acids with increased titers.     

Thyroid Carcinoma: Phenotypic Features,Underlying Biology and Potential Relevance for Targeting Therapy

Thyroid carcinoma consists a group of phenotypically heterogeneous cancers. Recent advances in biological technologies have been advancing the delineation of genetic, epigenetic, and non-genetic factors that contribute to the heterogeneities of these cancers. In this review article, we discuss new findings that are greatly improving the understanding of thyroid cancer biology and facilitating the identification of novel targets for therapeutic intervention. We review the phenotypic features of different subtypes of thyroid cancers and their underlying biology. We discuss recent discoveries in thyroid cancer heterogeneities and the critical mechanisms contributing to the heterogeneity with emphases on genetic and epigenetic factors, cancer stemness traits, and tumor microenvironments. We also discuss the potential relevance of the intratumor heterogeneity in understanding therapeutic resistance and how new findings in tumor biology can facilitate designing novel targeting therapies for thyroid cancer.     

Engineering Bacterial Cellulose by Synthetic Biology

Synthetic biology is an advanced form of genetic manipulation that applies the principles of modularity and engineering design to reprogram cells by changing their DNA. Over the last decade, synthetic biology has begun to be applied to bacteria that naturally produce biomaterials, in order to boost material production, change material properties and to add new functionalities to the resulting material. Recent work has used synthetic biology to engineer several Komagataeibacter strains; bacteria that naturally secrete large amounts of the versatile and promising material bacterial cellulose (BC). In this review, we summarize how genetic engineering, metabolic engineering and now synthetic biology have been used in Komagataeibacter strains to alter BC, improve its production and begin to add new functionalities into this easy-to-grow material. As well as describing the milestone advances, we also look forward to what will come next from engineering bacterial cellulose by synthetic biology.     

Optimizing the composition of cellulase enzyme complex from <Emphasis Type="Italic">Penicillium verruculosum</Emphasis>: Enhancing hydrolytic capabilities via genetic engineering

Modern technologies for the enzyme hydrolysis of cellulose-containing raw materials allow the production of sugars from which alcohols (biofuel), organic and amino acids, biopolymers, feed additives, and other value-added products can be obtained via microbiological conversion. Three types of cellulolytic enzymes are required for the bioconversion of cellulose containing materials: endoglucanase, cellobiohydrolase, and ß-glucosidase. The prospects for improving the hydrolytic capabilities of the enzyme complex secreted from Penicillium verruculosum are investigated in this work by means of genetic engineering to add different combinations and ratios of homologous and heterologous cellulases: endoglucanase IV (EGIV) of Trichoderma reesei, endoglucanase II (EGII), and cellobiohydrolase I (CBHI) of P. verruculosum, along with ß-glucosidase (ß-GLU) of Aspergillus niger. The optimum ratio of components is determined and the catalytic activity of enzymatic complexes is increased by as much as 100%.     

Effect of down-stream processing parameters on the mechanical properties of bacterial cellulose

Bacterial cellulose (BC), a biodegradable polymer with high degree of crystallinity, produced by Gluconacetobacter xylinus, was used as reinforcement in biocomposites. The downstream process parameters involved in the preparation process of BC have important influence on its mechanical properties. The effect of some key processing parameters such as treatment temperature, drying stages, type of treatment solvent and pressure on biocellulose sheets was investigated during drying in order to modify the parameters responsible in mechanical properties. The rise in treatment temperature and drying processes of BC sheets showed about 8 and 11 % reduction in tensile strength, respectively. The addition of NaOH solutions during the treatment reduced the tensile strength of BC sheets sharply, though an increase in NaOH concentration produced treated samples with higher tensile modulus. The use of optimum NaClO solution as a cheap treatment solvent led to an increase of about 10–11 % in the mechanical properties of BC. A pressure increase during drying stage improved the tensile strength of biocellulose sheets by 7 % and resulted in highly enhanced tensile modulus of BC samples. The production process (microbial fermentation) and structural features (porous web-shaped structure) provide an ideal scenario for synthesis of BC composites. A number of schemes have been introduced to synthesize BC composites with different materials. Among these schemes, the initial addition of materials to BC culture media, the treatment of BC with solutions and suspensions, and the dissolution of BC in solvents are the most commonly used techniques.     

Biosynthesis and characterization of novel polyhydroxyalkanoate copolymers consisting of 3-hydroxy-2-methylbutyrate and 3-hydroxyhexanoate

In this study, in order to explore the possibility of biosynthesizing a novel polyhydroxyalkanoate (PHA), copolymerization of 3-hydroxy-2-methylbutyrate (3H2MB) as the α-position methylated monomer and 3-hydroxyhexanoate (3HHx) as the medium-chain-length monomer was performed to obtain P(3H2MB-co-3HHx). The β-oxidation-deficient Escherichia coli LSBJ, harboring the PHA biosynthetic operon from Aeromonas caviae and the propionyl-CoA transferase gene (pct) from Megasphaera elsdenii, was cultured with feeding tiglic and hexanoic acids as the precursors for 3H2MB and 3HHx, respectively. It was observed that pct expression was highly effective to enhance the incorporation of 3H2MB into PHA. The biosynthesized PHA was composed of 3H2MB and 3HHx units only, and the 3H2MB fraction varied in the range of 36–60 mol% depending on the culture conditions. These PHAs exhibited glass transition temperatures between ?11 to ?17 °C; moreover, no melting peak was observed during analysis using differential scanning calorimetry. This study demonstrated the biosynthesis of a hitherto unreported PHA by engineering metabolic pathway in E. coli.     

Who Produces Ianthelline? The Arctic Sponge <Emphasis Type="Italic">Stryphnus fortis</Emphasis> or its Sponge Epibiont <Emphasis Type="Italic">Hexadella dedritifera</Emphasis>: a Probable Case of Sponge-Sponge Contamination

The bromotyrosine derivative ianthelline was isolated recently from the Atlantic boreo-arctic deep-sea sponge Stryphnus fortis, and shown to have clear antitumor and antifouling effects. However, chemosystematics, field observations, and targeted metabolic analyses (using UPLC-MS) suggest that ianthelline is not produced by S. fortis but by Hexadella dedritifera, a sponge that commonly grows on S. fortis. This case highlights the importance of combining taxonomic and ecological knowledge to the field of sponge natural products research.     

Heterogeneous oligomerization of light alkenes: 80 years in oil refining

Existing industrial technologies for the production of motor fuel compounds by the heterogeneous oligomerization of light С₂–С₄ alkenes are considered, along with ones promising for the practical use. Such basic types of systems used as heterogeneous catalysts in these processes as solid phosphoric acid, amorphous alumosilicates, zeolites, ion-exchange resins, anion-modified metal oxides, and nickel-containing catalysts, are described. Special attention is given to the dimerization of iso-butylene with the formation of iso-octene and its subsequent hydrogenation to iso-octane.     

微生物代谢工程：绘制细胞工厂的蓝图

代谢工程是一种理解并利用代谢过程的方法,其目的是优化或改变生物细胞中的代谢网络和表达调控网络,提高其代谢产物的产量或合成新的化合物.后基因组时代系统生物学和功能基因组学技术的发展,为构建能够实现特定目标的微生物细胞工厂提供了空前机遇.本文回顾代谢工程在技术和应用上的最新进展,讨论代谢工程中的关键问题和发展趋势,并提出中国在该领域的发展策略.     

Attraction of Three Mirid Predators to Tomato Infested by Both the Tomato Leaf Mining Moth <Emphasis Type="Italic">Tuta absoluta</Emphasis> and the Whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Plants emit volatile compounds in response to insect herbivory, which may play multiple roles as defensive compounds and mediators of interactions with other plants, microorganisms and animals. Herbivore-induced plant volatiles (HIPVs) may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. We report here the first evidence of the attraction of three Neotropical mirid predators (Macrolophus basicornis, Engytatus varians and Campyloneuropsis infumatus) toward plants emitting volatiles induced upon feeding by two tomato pests, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci, in olfactometer bioassays. Subsequently, we compared the composition of volatile blends emitted by insect-infested tomato plants by collecting headspace samples and analyzing them with GC-FID and GC-MS. Egg deposition by T. absoluta did not make tomato plants more attractive to the mirid predators than uninfested tomato plants. Macrolophus basicornis is attracted to tomato plants infested with either T. absoluta larvae or by a mixture of B. tabaci eggs, nymphs and adults. Engytatus varians and C. infumatus responded to volatile blends released by tomato plants infested with T. absoluta larvae over uninfested plants. Also, multiple herbivory by T. absoluta and B. tabaci did not increase the attraction of the mirids compared to infestation with T. absoluta alone. Terpenoids represented the most important class of compounds in the volatile blends and there were significant differences between the volatile blends emitted by tomato plants in response to attack by T. absoluta, B. tabaci, or by both insects. We, therefore, conclude that all three mirids use tomato plant volatiles to find T. absoluta larvae. Multiple herbivory did neither increase, nor decrease attraction of C. infumatus, E. varians and M. basicornis. By breeding for higher rates of emission of selected terpenes, increased attractiveness of tomato plants to natural enemies may improve the effectiveness of biological control.     

Genetic biosensors for small-molecule products: Design and applications in high-throughput screening

Overproduction of small-molecule chemicals using engineered microbial cells has greatly reduced the production cost and promoted environmental protection. Notably, the rapid and sensitive evaluation of the in vivo concentrations of the desired products greatly facilitates the optimization process of cell factories. For this purpose, many genetic components have been adapted into in vivo biosensors of small molecules, which couple the intracellular concentrations of small molecules to easily detectable readouts such as fluorescence, absorbance, and cell growth. Such biosensors allow a high-throughput screening of the small-molecule products, and can be roughly classified as protein-based and RNA-based biosensors. This review summarizes the recent developments in the design and applications of biosensors for small-molecule products.

Open image in new window

     

Expanding the repertoire of aromatic chemicals by microbial production

Microbial production of aromatic chemicals would greatly contribute to solving the problems with fossil resource supply and environmentally sustainable development. Engineering and extending the shikimate/aromatic amino acid biosynthetic pathways are important routes for microbial production of various aromatic chemicals. With advances in metabolic engineering and synthetic biology, we can broaden the product spectrum and obtain several valuable and novel aromatic chemicals from renewable feedstocks. Here, in this review, the latest research progress on microbial production of various aromatic chemicals, and recent metabolic engineering and synthetic biology strategies targeting the central carbon metabolism, the shikimate and aromatic amino acid biosynthetic pathways are summarized and discussed. This work aims to provide some valuable tips for the construction of cost‐effective engineered strains for producing various aromatic chemicals. © 2018 Society of Chemical Industry     

Application of synthetic biology in manufacture of bio-based plastics

Synthetic biology is a new discipline that uses engineering ideas as a guide to transform and reconstruct natural biological genomes, synthesize new biological components, construct new metabolic routes, and produce novel products or obtain new phenotypes. Bio-based plastics are plastics produced under the action of microorganisms or the chemical reactions using natural materials as raw materials. The usage of synthetic biology to construct engineered strains to produce bio-based plastics has become a hot topic in academia and industry. This paper reviews the development of synthetic biology and important techniques in the field of synthetic biology, focusing on the research progress in the field of metabolic pathways and engineering optimization for the construction of bio-based plastic polymer monomers and derivatives such as polyhydroxyalkanoate, nylon, polylactic acid, and butylene glycol succinate using synthetic biological techniques.     

合成生物学研究进展

合成生物学是以工程化设计思路,构建标准化的元器件和模块,改造已存在的天然系统或者从头合成全新的人工生命体系,实现在化学品合成(包括材料、能源和天然化合物)、医学、农业、环境等领域的应用。人们利用基本的生物学元件设计和构建了基因开关、振荡器、放大器、逻辑门、计数器等合成器件,实现对生命系统的重新编程并执行特殊功能。模块化处理生物的代谢途径,并在底盘细胞上进行组装和优化,可以实现大宗化学品和精细化学品的合成。目前人们已经在丁醇、异丁醇、青蒿素和紫杉醇等化合物的生物合成上取得了重要进展。近年来还发展了多种基因组编辑和组装技术,可精确地对基因组进行编辑,人们还成功地合成了噬菌体基因组、支原体基因组和酵母基因组。在未来的50～100年内,合成生物学将对人类的医疗、化学品制造(含药品)、军事产生渐进性的、渗透性的但颠覆性的意义。     

Phosphorylated cardanol prepolymer grafted guayule natural rubber: an advantageous green natural rubber

Natural rubber (HNR), produced from Hevea Brasiliensis, is being considered as the major source of 99.9% 1,4-cis-polyisoprene. Till date, this grade of natural rubber is not manufactured synthetically even using sophisticated solution polymerization techniques and utilizing the most advanced catalyst systems. Rubber industries have been continuously thriving for an alternative as well as an additional source of natural rubber to compensate for the reduction in production of Hevea natural rubber and to reduce the consumption of petroleum-based rubbers. The present study deals with chemical grafting of phosphorylated cardanol prepolymer (PCP) onto the main chain of guayule natural rubber (GNR), which could impart inherent multifunctional characteristics to the rubber. The grafting of PCP onto GNR was carried out successively using benzoyl peroxide as a free radical initiator in the solution stage and the grafting parameters have been optimized through the Taguchi method using grafting efficiency and percent grafting. Grafting of PCP onto GNR (PCP-g-GNR) was confirmed through UV–Visible, FTIR, NMR and GPC analysis. Thermal behavior of PCP-g-GNR indicates a significant increase in thermo-oxidative stability and it also displays a slight depression of glass transition temperature as compared to GNR. The viscoelastic characteristics of GNR also alter and cure characteristic improves drastically in giving rise to improved processability after grafting of the PCP. The unfilled PCP-g-GNR vulcanizates show approximately similar physico-mechanical properties with 5 phr processing oil as plasticized GNR vulcanizates. Therefore, PCP-g-GNR can be used in rubber industries as gum rubber materials as it reduces the usage of processing aids significantly.