Engineering Bacillus subtilis for production of 3-hydroxypropanoic acid.

3-Hydroxypropionic acid (3-HP) is a valuable platform chemical that is used as a precursor for several higher value-added chemical products. There is an increased interest in development of cell factories as a means for the synthesis of 3-HP and various other platform chemicals. For more than a decade, concentrated effort has been invested by the scientific community towards developing bio-based approaches for the production of 3-HP using primarily Escherichia coli and Klebsiella pneumoniae as production hosts. These hosts however might not be optimal for applications in e.g., food industry due primarily to endotoxin production and the pathogenic origin of particularly the K. pneumoniae. We have previously demonstrated that the generally recognized as safe organism Bacillus subtilis can be engineered to produce 3-HP using glycerol, an abundant by-product of the biodiesel industry, as substrate. For commercial exploitation, there is a need to substantially increase the titer. In the present study, we optimized the bioprocess conditions and further engineered the B. subtilis 3-HP production strain. Thereby, using glycerol as substrate, we were able to improve 3-HP production in a 1-L bioreactor to a final titer of 22.9 g/L 3-HP.

Targeted manipulation of bZIP53 DNA-binding properties influences Arabidopsis metabolism and growth.

bZIP transcription factors regulate diverse processes in eukaryotic cells. Arabidopsis bZIP members of the C and S1 groups form heterodimers and synergistically control metabolic reprogramming during stress responses. However, their functional characterization is complicated due to an overlapping heterodimerization network and high redundancy. In this study, we develop a simple but powerful approach for generating dominant negative mutants of bZIP factors with high specificity. By applying in vitro DNA-binding, reporter gene and protoplast two-hybrid assays, and plant mutant analysis, we show that phosphorylation-mimicking substitution of conserved serines in the DNA-binding domain of bZIP monomeric subunits suffices for the disruption of the interaction of both bZIP homo- and heterodimers with cognate DNA. This results in the transcriptional inactivation of target genes. The dominant-negative effect is achieved by the unaltered function of the intrinsic nuclear localization signal and dimerization properties of the mutated bZIP protein. Our findings not only reveal an additional regulatory mechanism of bZIP10 intracellular localization, but also provide evidence of the involvement of bZIP53 in the diurnal adjustments of amino acid metabolism. Our data demonstrate the advantages and the suitability of this new approach for the artificial inactivation of bZIP transcription factors in plants, and it may also be of use for other organisms.

Production of 3-Hydroxypropanoic Acid From Glycerol by Metabolically Engineered Bacteria.

3-hydroxypropanoic acid (3-HP) is a valuable platform chemical with a high demand in the global market. 3-HP can be produced from various renewable resources. It is used as a precursor in industrial production of a number of chemicals, such as acrylic acid and its many derivatives. In its polymerized form, 3-HP can be used in bioplastic production. Several microbes naturally possess the biosynthetic pathways for production of 3-HP, and a number of these pathways have been introduced in some widely used cell factories, such as Escherichia coli and Saccharomyces cerevisiae. Latest advances in the field of metabolic engineering and synthetic biology have led to more efficient methods for bio-production of 3-HP. These include new approaches for introducing heterologous pathways, precise control of gene expression, rational enzyme engineering, redirecting the carbon flux based on in silico predictions using genome scale metabolic models, as well as optimizing fermentation conditions. Despite the fact that the production of 3-HP has been extensively explored in established industrially relevant cell factories, the current production processes have not yet reached the levels required for industrial exploitation. In this review, we explore the state of the art in 3-HP bio-production, comparing the yields and titers achieved in different microbial cell factories and we discuss possible methodologies that could make the final step toward industrially relevant cell factories.

Antimicrobial Effects of Biogenic Nanoparticles.

Infectious diseases pose one of the greatest health challenges in the medical world. Though numerous antimicrobial drugs are commercially available, they often lack effectiveness against recently developed multidrug resistant (MDR) microorganisms. This results in high antibiotic dose administration and a need to develop new antibiotics, which in turn requires time, money, and labor investments. Recently, biogenic metallic nanoparticles have proven their effectiveness against MDR microorganisms, individually and in synergy with the current/conventional antibiotics. Importantly, biogenic nanoparticles are easy to produce, facile, biocompatible, and environmentally friendly in nature. In addition, biogenic nanoparticles are surrounded by capping layers, which provide them with biocompatibility and long-term stability. Moreover, these capping layers provide an active surface for interaction with biological components, facilitated by free active surface functional groups. These groups are available for modification, such as conjugation with antimicrobial drugs, genes, and peptides, in order to enhance their efficacy and delivery. This review summarizes the conventional antibiotic treatments and highlights the benefits of using nanoparticles in combating infectious diseases.

Gold Nanoparticles in Diagnostics and Therapeutics for Human Cancer.

The application of nanotechnology for the treatment of cancer is mostly based on early tumor detection and diagnosis by nanodevices capable of selective targeting and delivery of chemotherapeutic drugs to the specific tumor site. Due to the remarkable properties of gold nanoparticles, they have long been considered as a potential tool for diagnosis of various cancers and for drug delivery applications. These properties include high surface area to volume ratio, surface plasmon resonance, surface chemistry and multi-functionalization, facile synthesis, and stable nature. Moreover, the non-toxic and non-immunogenic nature of gold nanoparticles and the high permeability and retention effect provide additional benefits by enabling easy penetration and accumulation of drugs at the tumor sites. Various innovative approaches with gold nanoparticles are under development. In this review, we provide an overview of recent progress made in the application of gold nanoparticles in the treatment of cancer by tumor detection, drug delivery, imaging, photothermal and photodynamic therapy and their current limitations in terms of bioavailability and the fate of the nanoparticles.

The low energy signaling network.

Stress impacts negatively on plant growth and crop productivity, caicultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy-saving responses. The resulting low energy syndrome (LES) includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases sucrose-non-fermenting-1-related protein kinase-1 (SnRK1) and target of rapamycin (TOR) play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments.