Prospecting Microbial Genomes for Biomolecules and Their Applications.

Bioactive molecules of microbial origin are finding increasing biotechnological applications. Their sources range from the terrestrial, marine, and endophytic to the human microbiome. These biomolecules have unique chemical structures and related groups, which enable them to improve the efficiency of the bioprocesses. This review focuses on the applications of biomolecules in bioremediation, agriculture, food, pharmaceutical industries, and human health.

Characterization of a xylitol dehydrogenase from Aspergillus flavus and its application in l-xylulose production.

An NAD+-dependent xylitol dehydrogenase from A. flavus (AfXDH) was cloned and successfully expressed in Escherichia coli. AfXDH gene sequence revealed an open reading frame of 1,110 bp, encoding a polypeptide of 369 amino acids with a calculated molecular mass of 38,893 Da. Among various polyols, sorbitol and xylitol were preferred substrates of AfXDH with Km values of 16.2 and 16.9 mM, respectively. AfXDH showed the highest activity in Tris-glycine-NaOH buffer (pH 9.5) at 50°C; it required Zn2+ or Mn2+ for enzyme activity. The half-life at 40°C and half denaturation temperature (T1/2) was 200 min and 45°C, respectively. Bioinformatic analyses along with biochemical properties confirmed that AfXDH belonged to the medium-chain dehydrogenase/reductase family. AfXDH exhibits higher thermostability and k cat values than those of other XDHs. The feasibility of using AfXDH in l-xylulose production was demonstrated. AfXDH, when coupled with Streptococcus pyogenes NADH oxidase, efficiently converted xylitol to l-xylulose with 97% yield, suggesting its usefulness for the industrial l-xylulose production from xylitol.

The Emerging Biotherapeutic Agent: Akkermansia.

The human gastrointestinal tract (GIT) is a well-recognized hub of microbial activities. The microbiota harboring the mucus layer of the GIT act as a defense against noxious substances, and pathogens including Clostridium difficile, Enterococcus faecium, Escherichia coli, Salmonella Typhimurium. Toxins, pathogens, and antibiotics perturb the commensal floral composition within the GIT. Imbalanced gut microbiota leads to dysbiosis, manifested as diseases ranging from obesity, diabetes, and cancer to reduced lifespan. Among the bacteria present in the gut microbiome, the most beneficial are those representing Firmicutes and Bacteroidetes. Recent studies have revealed the emergence of a novel biotherapeutic agent, Akkermansia, which is instrumental in regaining eubiosis and conferring various health benefits.

Azulene Bridged π-Distorted Chromophores: The Influence of Structural Symmetry on Optoelectrochemical and Photovoltaic Parameters.

Conjugated chromophores possessing π-twisted functionality such as tetracyanobutadiene (TCBD) have emerged as promising active layer materials for organic photovoltaics (OPVs). In this study, we disclose the synthesis of two azulenyl chromophores containing one and two TCBD groups. The symmetrical and unsymmetrical structural characteristics of these molecules inflict dissimilar optoelectronic and electrochemical properties. Based on molar absorptivity, aggregation behavior, HOMO-LUMO energies and other quantum chemical parameters, the symmetrical molecule (TATC2) appears to be a better non-fullerene acceptor (NFA) compared to its unsymmetrical counterpart (TATC1). For instance, higher absorptivity and deeper HOMO-LUMO levels for TATC2 (23950 M-1 cm-1 ; -6.01 eV/-3.86 eV) over TATC1 (12200 M1 cm-1 ; -5.46 eV/-3.64 eV) was observed. Validating this structure-property relationship on solar cell prototypes exhibited higher photovoltaic parameters (VOC =0.54 V, FF=0.48, JSC =6.42 mA/cm2 ) for TATC2 than TATC1 (VOC =0.47 V, FF=0.38, JSC =5.77 mA/cm2 ). Though the device parameters are not high, this work uncovers the intrinsic properties of azulene-tethered twisted chromophores as potential π-semiconductor choice for NFA solar cells. In particular, this report explores the utility of azulene-based π-twisted semiconductors as acceptor material for OPVs with cell efficiencies of 1.70 and 1.04 % for TATC2 and TATC1 respectively.

Biotin and Zn2+ Increase Xylitol Production by Candida tropicalis.

In this study, the medium requirements to increase the production of xylitol by using Candida tropicalis (CT) have been investigated. The technique of single addition or omission of medium components was applied to determine the nutritional requirements. The addition of amino acids such as Asp, Glu, Gln, Asn, Thr, and Gly had no significant effect on CT growth. However, in the absence of other metal ions, there was a higher concentration of cell growth and xylitol production when only Zn2+ was present in the medium. The analysis of various vitamins unveiled that biotin and thiamine were the only vitamins required for the growth of CT. Surprisingly, when only biotin was present in the medium as a vitamin, there was less growth of CT than when the medium was complete, but the amount of xylitol released was significantly higher. Overall, this study will increase the xylitol production using the single omission or addtion technique.

Site-directed lysine modification of xylanase for oriented immobilization onto silicon dioxide nanoparticles.

Enhanced covalent immobilization of xylanase from Chaetomium globosum (XylCg) onto SiO2 nanoparticles was achieved by the modification of surface residues. The mutation of surface residues to lysine by site-directed mutagenesis increased the immobilization efficiency (IE) and immobilization yield (IY). The immobilized mutant XylCg (N172K-H173K-S176K-K133A-K148A) exhibited an IY of 99.5% and IE of 135%, which were 1.8- and 4.3-fold higher than immobilized wildtype (WT). Regarding the catalytic properties, the kcat and kcat/Km values were 1850 s-1 and 2030 mL mg-1 s-1 for the immobilized mutant, and 331 s-1 and 404 mL mg-1 s-1 for the immobilized WT, respectively. Additionally, the immobilized mutant exhibited four times higher thermal stability than the immobilized WT at 60 °C. These results suggest that surface-mutated lysine residues confer good stability and orientation on the support matrix, thus improving the overall performance of xylanase.

Polyhydroxyalkanoates: Trends and advances toward biotechnological applications.

Plastics are an integral part of most of the daily requirements. Indiscriminate usage and disposal have led to the accumulation of massive quantities of waste. Their non-biodegradable nature makes it increasingly difficult to manage and dispose them. To counter this impending disaster, biodegradable polymers, especially polyhydroxy-alkanoates (PHAs), have been envisaged as potential alternatives. Owing to their unique physicochemical characteristics, PHAs are gaining importance for versatile applications in the agricultural and medical sectors. Applications in the medical sector are more promising because of their commercial viability and sustainability. Despite such potential, their production and commercialization are significant challenges. The major limitations are their poor mechanical strength, production in small quantities, costly feed, and lack of facilities for industrial production. This article provides an overview of the contemporary progress in the field, to attract researchers and stakeholders to further exploit these renewable resources to produce biodegradable plastics on a commercial scale.

Tyr320 is a molecular determinant of the catalytic activity of ß-glucosidase from Neosartorya fischeri.

ß-Glucosidases (BGL) are key members of the cellulase enzyme complex that determine efficiency of lignocellulosic biomass degradation, which have shown great functional importance to many biotechnological systems. A previous reported BGL from Neosartorya fischeri (NfBGL) showed much higher activity than other BGLs. Screening the important residues based on sequence alignment, analyzing a homology model, and subsequent alteration of individually screened residues by site-directed mutagenesis were carried out to investigate the molecular determinants of the enzyme's high catalytic efficiency. Tyr320, located in the wild-type NfBGL substrate-binding pocket was identified as crucial to the catalytic function of NfBGL. The replacement of Tyr320 with aromatic amino acids did not significantly alter the catalytic efficiency towards p-nitrophenyl ß-d-glucopyranoside (pNPG). However, mutants with charged and hydrophilic amino acids showed almost no activity towards pNPG. Computational studies suggested that an aromatic acid is required at position 320 in NfBGL to stabilize the enzyme-substrate complex formation. This knowledge on the mechanism of action of the molecular determinants can also help rational protein engineering of BGLs.

Methanol production by polymer-encapsulated methanotrophs from simulated biogas in the presence of methane vector.

Type I (Methylomicrobium album) and II (Methyloferula stellata) methanotrophs were encapsulated by alginate and polyvinyl alcohol (PVA) to improve methanol production from simulated biogas [methane (CH4) and carbon dioxide (CO2)] in the presence of CH4 vector. Polymeric matrix alginate (2%) and PVA (10%) were found to be optimum for the immobilization of both the methanotrophs, with a relative efficiency of methanol production up to 80.6 and 88.7%, respectively. The stability of methanol production by immobilized cells was improved up to 13.2-fold under repeated batch-culture over free cells. The addition of CH4 vectors showed 1.7-fold higher methanol production on using simulated biogas than in the control. The maximum methanol production of 7.46 and 7.14 mmol/L was noted for PVA-encapsulated M. album and M. stellata, respectively. This study successfully established the beneficial effects of CH4 vectors on methanol production by methanotrophs from greenhouse gases that can be applied for real biogas feedstock.

Phosphine oxide-based tricarbonylrhenium(i) complexes from phosphine/phosphine oxide and dihydroxybenzoquinones.

Neutral phosphine oxide (P[double bond, length as m-dash]O) donor-based organometallic complexes [{Re(CO)3O[double bond, length as m-dash]PCy3}{µ-DHBQ}{Re(CO)3O[double bond, length as m-dash]PCy3}] (1), [{Re(CO)3O[double bond, length as m-dash]PPh3}{µ-DHBQ}{Re(CO)3O[double bond, length as m-dash]PPh3}] (2), [{Re(CO)3O[double bond, length as m-dash]PCy3}{µ-THQ}{Re(CO)3O[double bond, length as m-dash]PCy3}] (3), [{Re(CO)3O[double bond, length as m-dash]PPh3}{µ-THQ}{Re(CO)3O[double bond, length as m-dash]PPh3}] (4), [{Re(CO)3O[double bond, length as m-dash]PCy3}{µ-CA}{Re(CO)3O[double bond, length as m-dash]PCy3}] (5), and [{Re(CO)3O[double bond, length as m-dash]PPh3}{µ-CA}{Re(CO)3O[double bond, length as m-dash]PPh3}] (6) were assembled from phosphine/phosphine oxide, a dihydroxybenzoquinone donor and Re2(CO)10via a one-pot solvothermal approach. The soft phosphine donor was transformed into a hard phosphine oxide donor during the formation of 1, 3, 4, 5, and 6. The complexes 1-6 were air and moisture stable and were soluble in polar organic solvents. The complexes were characterized by elemental analysis, FT-IR, and NMR spectroscopic methods. The molecular structures of 1, 2, 4, and 6 were analyzed by single-crystal X-ray diffraction analysis. The UV-Visible absorption studies indicated that 1-6 in THF display strong visible light absorption in the range of ∼350-700 nm.

Targeting the cyclin-binding groove site to inhibit the catalytic activity of CDK2/cyclin A complex using p27(KIP1)-derived peptidomimetic inhibitors.

Functionally activated cyclin-dependent kinase 2 (CDK2)/cyclin A complex has been validated as an interesting therapeutic target to develop the efficient antineoplastic drug based on the cell cycle arrest. Cyclin A binds to CDK2 and activates the kinases as well as recruits the substrate and inhibitors using a hydrophobic cyclin-binding groove (CBG). Blocking the cyclin substrate recruitment on CBG is an alternative approach to override the specificity hurdle of the currently available ATP site targeting CDK2 inhibitors. Greater understanding of the interaction of CDK2/cyclin A complex with p27 (negative regulator) reveals that the Leu-Phe-Gly (LFG) motif region of p27 binds with the CBG site of cyclin A to arrest the malignant cell proliferation that induces apoptosis. In the present study, Replacement with Partial Ligand Alternatives through Computational Enrichment (REPLACE) drug design strategies have been applied to acquire LFG peptide-derived peptidomimetics library. The peptidomimetics function is equivalent with respect to substrate p27 protein fashion but does not act as an ATP antagonist. The combined approach of molecular docking, molecular dynamics (MD), and molecular electrostatic potential and ADME/T prediction were carried out to evaluate the peptidomimetics. Resultant interaction and electrostatic potential maps suggested that smaller substituent is desirable at the position of phenyl ring to interact with Trp217, Arg250, and Gln254 residues in the active site. The best docked poses were refined by the MD simulations which resulted in conformational changes. After equilibration, the structure of the peptidomimetic and receptor complex was stable. The results revealed that the various substrate protein-derived peptidomimetics could serve as perfect leads against CDK2 protein.

Crystal structure of bis-(4-acetyl-anilinium) tetra-chlorido-cobaltate(II).

The structure of the title salt, (C8H10NO)2[CoCl4], is isotypic with the analogous cuprate(II) structure. The asymmetric unit contains one 4-acetyl-anilinium cation and one half of a tetra-chlorido-cobaltate(II) anion for which the Co(II) atom and two Cl(-) ligands lie on a mirror plane. The Co-Cl distances in the distorted tetra-hedral anion range from 2.2519 (6) to 2.2954 (9) Šand the Cl-Co-Cl angles range from 106.53 (2) to 110.81 (4)°. In the crystal, cations are self-assembled by inter-molecular N-H⋯O hydrogen-bonding inter-actions, leading to a C(8) chain motif with the chains running parallel to the b axis. π-π stacking inter-actions between benzene rings, with a centroid-to-centroid distance of 3.709 Å, are also observed along this direction. The CoCl4 (2-) anions are sandwiched between the cationic chains and inter-act with each other through inter-molecular N-H⋯Cl hydrogen-bonding inter-actions, forming a three-dimensional network structure.

New class of phosphine oxide donor-based supramolecular coordination complexes from an in situ phosphine oxidation reaction or phosphine oxide ligands.

A one-pot, multicomponent, coordination-driven self-assembly approach was used to synthesize the first examples of neutral bridging phosphine oxide donor-based supramolecular coordination complexes. The complexes were self-assembled from a fac-Re(CO)3 acceptor, an anionic bridging O donor, and a neutral soft phosphine or hard phosphine oxide donor.

Furan-decorated neutral Re(I)-based 2D rectangle and 3D trigonal prism.

Neutral, stable and luminescent metallacycles decorated with furan units, a 2D rectangle with four furans and a 3D trigonal prism with six furans, were synthesized from readily accessible starting materials through a fac-Re(CO)(3)-directed approach.