Characterization of hydrocortisone bioconversion and 16S RNA gene in Synechococcus nidulans cultures

A unicellular cyanobacterium, Synechococcus nidulans (Pringsheim) Komárek, was isolated from paddy-fields and applied in the biotransformation experiment of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25°C for 14 days of incubation. The products obtained were chromatographically purified followed by their characterization using spectroscopic methods, 11β,17β-dihydroxyandrost-4-en-3-one (2), 11β-hydroxyandrost-4-en-3,17-dione (3), and androst-4-ene-3,17-dione (4) were the main bioproducts in the hydrocortisone bioconversion. The observed bioreaction characteristics were the side chain degradation of the substrate to prepare compounds (2) and (3) following the 11β-dehydroxylation for accumulation of the compound (4). Time course study showed the accumulation of the product (2) from the second day of the fermentation and compounds (3) and (4) from the third day. All the metabolites reached their maximum concentration in seven days. Cyanobacterial 16S rRNA gene was also amplified by PCR. Sequences were amplified using the universal prokaryotic primers which amplify a ～400-bp region of the 16S rRNA gene. PCR products were sequenced to confirm their authenticity as 16S rRNA gene of cyanobacteria. The result of PCR blasted with other sequenced cyanobacteria in NCBI showed 99% identity to the 16S small subunit rRNA of seven Synechococcus species.     

Experimental Evaluation of In Silico Selected Signal Peptides for Secretory Expression of Erwinia Asparaginase in Escherichia coli

International Journal of Peptide Research and Therapeutics - Erwinia chrysanthemi asparaginase is an important drug used in cancer treatment, especially in acute lymphoblastic leukemia (ALL)....     

Biotransformation of monoterpenes by Oocystis pusilla

The biotransformation of several monoterpenes by the locally isolated unicellular microalga, Oocystis pusilla was investigated. The metabolites were identified by thin layer chromatography and GC/MS. The results showed that O. pusilla had the ability to reduce the C=C double bond in (+)-carvone to yield trans-dihydrocarvone and traces of cis-dihydrocarvone. O. pusilla also converted (+)-limonene to trans-carveol, as the main product, and yielded carvone and trans-limonene oxide. Furthermore, (−)-linalool was converted to trans-furanoid and trans-pyranoid linalool oxide, thymol was converted to thymoquinone, (−)-carveol was converted to carvone and trans-dihydrocarvone, (−)-menthone and (+)-pulegone were converted to menthol, (L)-citronellal was converted to citronellol, and (+)-β-pinene was converted to trans-pinocarveol.     

Vaccinomics approach for developing multi-epitope peptide pneumococcal vaccine

Streptococcus pneumoniae is a leading cause of some diseases such as pneumonia, sepsis, and meningitis mostly in children less than 5?years of age. Presently, two types of pneumococcal vaccine are available on the market: polysaccharide vaccines (PPV) that are based on capsular polysaccharides of at least 92 different serotypes, and protein-conjugated polysaccharide vaccine (PCV). The PPVs such as PPV23 do not stimulate efficient protective immunity in children under 2?years old, while the PCVs such as PCV7, PCV10, and PCV13 that cover 7, 10, and 13 serotypes, respectively, highly protect newborns, but have some disadvantages such as complications in manufacturing, costly production, and also requires refrigeration and multiple injections. Epitope-based vaccines, including varied mixtures of conserved virulence proteins, are a promising alternative to the existing capsular antigen vaccines. In this study, it has been tried to design an efficient subunit vaccine in order to elicit both CTL and HTL responses. The immunodominant epitopes from highly protective antigens of S. pneumoniae (PspA, CbpA, PiuA, and PhtD) were selected from different databanks, such as IEDB, PROPRED, RANKPEP, and MHCPRED. The PspA and CbpA were chosen as CTL epitope stimulants, and PhtD and PiuA were defined as helper epitopes. Because of low immunogenicity of epitope vaccines, PorB protein as a TLR2 agonist was employed to increase the immunogenicity of the vaccine. All the peptide segments were fused to each other by proper linkers, and the physicochemical, structural, and immunological characteristics of the construct were also evaluated. To achieve a high-quality 3?D structure of the protein, modeling, refinement, and validation of the final construct were done. Docking and molecular dynamics analyses demonstrated an appropriate and stable interaction between the vaccine and TLR2 during the simulation period. The computational studies suggested the designed vaccine as a novel construct, capable to elicit efficient humoral and cellular immunities, which are crucial for protection against S. pneumoniae.

Communicated by Ramaswamy H. Sarma     

Modification in media composition to obtain secretory production of STxB-based vaccines using Escherichia coli

Shiga toxin B-subunit (STxB) from Shigella dysenteriae targets in vivo antigen to cancer cells, dendritic cells (DC) and B cells, which preferentially express the globotriaosylceramide (Gb3) receptor. This pivotal role has encouraged scientists to investigate fusing STxB with other clinical antigens. Due to the challenges of obtaining a functional soluble form of the recombinant STxB, such as formation of inclusion bodies during protein expression, scientists tend to combine STxB with vaccine candidates rather than using their genetically fused forms. In this work, we fused HPV16 E7 as a vaccine candidate to the recombinantly-produced STxB. To minimize the formation of inclusion bodies, we investigated a number of conditions during the expression procedure. Then various strategies were used in order to obtain high yield of soluble recombinant protein from E. coli which included the use of different host strains, reduction of cultivation temperature, as well as using different concentrations of IPTG and different additives (Glycin, Triton X-100, ZnCl₂). Our study demonstrated the importance of optimizing incubation parameters for recombinant protein expression in E. coli; also showed that the secretion production can be achieved over the course of a few hours when using additives such as glycine and Triton X-100. Interestingly, it was shown that when the culture mediums were supplemented by additives, there was an inverse ratio between time of induction (TOI) and the level of secreted protein at lower temperatures. This study determines the optimal conditions for high yield soluble E7-STxB expression and subsequently facilitates reaching a functionally soluble form of STxB-based vaccines, which can be considered as a potent vaccine candidate for cervical cancer.