Optimization of Siderophore Production in Three Marine Bacterial Isolates along with Their Heavy-Metal Chelation and Seed Germination Potential Determination.

Siderophores are low-molecular-weight and high-affinity molecules produced by bacteria under iron-limited conditions. Due to the low iron (III) (Fe+3) levels in surface waters in the marine environment, microbes produce a variety of siderophores. In the current study, halophilic bacteria Bacillus taeanensis SMI_1, Enterobacter sp., AABM_9, and Pseudomonas mendocina AMPPS_5 were isolated from marine surface water of Kalinga beach, Bay of Bengal (Visakhapatnam, Andhra Pradesh, India) and were investigated for siderophore production using the Chrome Azurol S (CAS) assay. The effect of various production parameters was also studied. The optimum production of siderophores for SMI_1 was 93.57% siderophore units (SU) (after 48 h of incubation at 30 °C, pH 8, sucrose as carbon source, sodium nitrate as nitrogen source, 0.4% succinic acid), and for AABM_9, it was 87.18 %SU (after 36 h of incubation period at 30 °C, pH 8, in the presence of sucrose, ammonium sulfate, 0.4% succinic acid). The maximum production of siderophores for AMPPS_5 was 91.17 %SU (after 36 h of incubation at 35 °C, pH 8.5, glucose, ammonium sulfate, 0.4% citric acid). The bacterial isolates SMI_1, AABM_9, and AMPPS_5 showed siderophore production at low Fe+3 concentrations of 0.10 µM, 0.01 µM, and 0.01 µM, respectively. The SMI_1 (73.09 %SU) and AMPPS_5 (68.26 %SU) isolates showed siderophore production in the presence of Zn+2 (10 µM), whereas AABM_9 (50.4 %SU) exhibited siderophore production in the presence of Cu+2 (10 µM). Additionally, these bacterial isolates showed better heavy-metal chelation ability and rapid development in seed germination experiments. Based on these results, the isolates of marine-derived bacteria effectively produced the maximum amount of siderophores, which could be employed in a variety of industrial and environmental applications.

Characterization, catalytic, and recyclability studies of nano-sized spherical palladium particles synthesized using aqueous poly-extract (turmeric, neem, and tulasi).

Green synthesis of noble metal nanoparticles (NPs) has gained immense significance compared to other metal ions owing to their unique properties. Among them, palladium 'Pd' has been in the spotlight for its stable and superior catalytic activity. This work focuses on the synthesis of Pd NPs using the combined aqueous extract (poly-extract) of turmeric (rhizome), neem (leaves), and tulasi (leaves). The bio-synthesized Pd NPs were characterized to study its physicochemical and morphological features using several analytical techniques. Role of Pd NPs as nano-catalysts in the degradation of dyes (1 mg/2 mL stock solution) was evaluated in the presence of a strong reducing agent (sodium borohydride; SBH). In the presence of Pd NPs and SBH, maximum reduction of methylene blue (MB), methyl orange (MO), and rhodamine-B (Rh-B) dyes was observed under 20nullmin (96.55 ± 2.11%), 36nullmin (96.96 ± 2.24%), and 27nullmin (98.12 ± 1.33%), with degradation rate of 0.1789 ± 0.0273 min-1, 0.0926 ± 0.0102 min-1, and 0.1557 ± 0.0200 min-1, respectively. In combination of dyes (MB + MO + Rh-B), maximum degradation was observed under 50nullmin (95.49 ± 2.56%) with degradation rate of 0.0694 ± 0.0087 min-1. It was observed that degradation was following pseudo-first order reaction kinetics. Furthermore, Pd NPs showed good recyclability up to cycle 5 (72.88 ± 2.32%), cycle 9 (69.11 ± 2.19%) and cycle 6 (66.21 ± 2.72%) for MB, MO and Rh-B dyes, respectively. Whereas, up to cycle 4 (74.67 ± 0.66%) during combination of dyes. As Pd NPs showed good recyclability, they can be used for several cycles thus influencing the overall economics of the process.

Effect of size on physicochemical, antibacterial, and catalytic properties of Neolamarckia cadamba (burflower-tree) synthesized silver/silver chloride nanoparticles.

Aqueous extract of Neolamarchia cadamba leaves were used in the synthesis of silver/silver chloride nanoparticles (Ag/AgCl NPs). Further they were separated based on their using step-wise centrifugation approach at 09,000, 12,000, and 15,000 rpm. Thus obtained NPs were characterized for their physicochemical features. NPs showed maximum absorbance at 455 nm, 415 nm, and 402 nm. All the NPs were found to be crystalline in nature with average crystallite size (nm) of 58.31, 23.43, and 09.56. Particle size distribution (nm) of NPs was observed to 435.43, 276.75, and 105.49, Surface charge (-mV) of NPs was observed to be 14.59, 23.90, and 32.17. Ag/AgCl NPs-rpm@15,000 showed antibacterial activity against Escherichia coli, coagulase-negative Staphylococci, and Staphylococcus aureus with zone of inhibition (mm) of 16.65, 13.69, and 14.02 at 50 µg per well, respectively. Ag/AgCl NPs-rpm@15,000 showed excellent catalytic activity in degradation of methyl red, methylene blue, rhodamine-B, and methyl orange dyes in the presence of sodium borohydride under 4, 6, 5, and 4 min with pseudo-first order rate constant (min-1) of 0.981 (96.4%), 0.666 (97.1%), 0.905 (98.1%), and 1.032 (96.6%), respectively. Furthermore, Ag/AgCl NPs-rpm@15,000 showed good catalytic efficiency even under different dye combinations. Total combination was degraded under 18 min.

Role of metagenomics in prospecting novel endoglucanases, accentuating functional metagenomics approach in second-generation biofuel production: a review.

As the fossil fuel reserves are depleting rapidly, there is a need for alternate fuels to meet the day to day mounting energy demands. As fossil fuel started depleting, a quest for alternate forms of fuel was initiated and biofuel is one of its promising outcomes. First-generation biofuels are made from edible sources like vegetable oils, starch, and sugars. Second-generation biofuels (SGB) are derived from lignocellulosic crops and the third-generation involves algae for biofuel production. Technical challenges in the production of SGB are hampering its commercialization. Advanced molecular technologies like metagenomics can help in the discovery of novel lignocellulosic biomass-degrading enzymes for commercialization and industrial production of SGB. This review discusses the metagenomic outcomes to enlighten the importance of unexplored habitats for novel cellulolytic gene mining. It also emphasizes the potential of different metagenomic approaches to explore the uncultivable cellulose-degrading microbiome as well as cellulolytic enzymes associated with them. This review also includes effective pre-treatment technology and consolidated bioprocessing for efficient biofuel production.

Biogenic synthesis of novel platinum-palladium bimetallic nanoparticles from aqueous Annona muricata leaf extract for catalytic activity.

This work reports the fast and effective bio-fabrication of novel platinum-palladium bimetallic nanoparticles (Pt-Pd BNPs) along with their counterparts Pt and Pd monometallic NPs (MNPs) through aqueous Annona muricata leaf extract. The bio-fabrication of the NPs was achieved within 2 h at 100 °C and pH 7 which was established by the occurrence of dark brown color for Pt MNPs and black color for Pd MNPs and Pt-Pd BNPs. NPs were evaluated for their catalytic activity in the reduction of methyl orange (MO), rhodamine-B (rh-B), and methylene blue (MB) textile dyes in presence of sodium borohydride as a reducing agent. Pt-Pd (1:3) BNPs showed higher MO dye degradation (96.84 ± 2.05% in 50 min) followed by Pd MNPs (97.07 ± 1.46% in 60 min), Pt-Pd (3:1) BNPs (97.34 ± 1.17% in 70 min) and Pt-Pd (1:1) BNPs (98.12 ± 1.04% in 80 min). Pd MNPs showed significant catalytic activity in the reduction of rh-B dye by 97.27 ± 1.14% in 12 min followed by Pt-Pd (3:1) BNPs (96.76 ± 2.17% in 18 min), Pt-Pd (1:3) BNPs (96.53 ± 1.97% in 33 min) and Pt-Pd (1:1) BNPs (97.11 ± 2.09% in 39 min). Pt-Pd (1:3) BNPs also showed higher MB dye degradation (96.95 ± 1.57% in 40 min) followed by Pd MNPs (96.22 ± 2.36% in 55 min), Pt-Pd (3:1) BNPs (97.29 ± 1.22% in 75 min) and Pt-Pd (1:1) BNPs (96.45 ± 2.19% in 105 min). However, Pt MNPs showed no catalytic activity. Standard disc diffusion method was used to evaluate the NPs toxicity towards Escherichia coli and Staphylococcus aureus, which showed no inhibitory zones. NPs showed less toxicity compared to potassium dichromate (control) against Artemia nauplii. Among the NPs studied, Pt-Pd (1:1) BNPs showed less toxicity with 100% mortality only at 100 µg/mL concentration followed by Pt MNPs (≥ 80 µg/mL), Pt-Pd (1:3) BNPs (≥ 60 µg/mL), Pt-Pd (3:1) BNPs (≥ 60 µg/mL) and Pd MNPs (≥ 40 µg/mL) after 72 h exposure. These evaluations support the application of bio-fabricated Pt-Pd BNPs as nano-catalysts in textile dyes degradation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02935-0.

Assessment of properties, applications and limitations of scaffolds based on cellulose and its derivatives for cartilage tissue engineering: A review.

Cartilage is a connective tissue, which is made up of ~80% of water. It is alymphatic, aneural and avascular with only one type of cells present, chondrocytes. They constitute about 1-5% of the entire cartilage tissue. It has a very limited capacity for spontaneous repair. Articular cartilage defects are quite common due to trauma, injury or aging and these defects eventually lead to osteoarthritis, affecting the daily activities. Tissue engineering (TE) is a promising strategy for the regeneration of articular cartilage when compared to the existing invasive treatment strategies. Cellulose is the most abundant natural polymer and has desirable properties for the development of a scaffold, which can be used for the regeneration of cartilage. This review discusses about (i) the basic science behind cartilage TE and the study of cellulose properties that can be exploited for the construction of the engineered scaffold with desired properties for cartilage tissue regeneration, (ii) about the requirement of scaffolds properties, fabrication mechanisms and assessment of cellulose based scaffolds, (iii) details about the modification of cellulose surface by employing various chemical approaches for the production of cellulose derivatives with enhanced characteristics and (iv) limitations and future research prospects of cartilage TE.

Novel buffalo rumen metagenome derived acidic cellulase Cel-3.1 cloning, characterization, and its application in saccharifying rice straw and corncob biomass.

Lignocellulosic biomass (LCB) is a prominent option for second-generation biofuels production. Cellulase hydrolyses cellulose, a component of LCB by attacking the ß-1,4-glycosidic bonds, thus liberating mono, di, and oligosaccharides, which subsequently, can be converted to biofuel. In this study, a novel cellulase (Cel-3.1) of 1593 bp which encodes a 530 amino acid protein was identified from buffalo rumen metagenomic fosmid library, and functional expression was achieved through transformation into Escherichia coli. The molecular weight was estimated as 58 kDa on SDS-PAGE. Cel-3.1 belongs to glycosyl hydrolase family-5 (GH-5) and is predicted to have 14 α-helices and 15 ß-strands. The optimal temperature and pH for Cel-3.1 were experimentally determined as 5.0 and 50 °C respectively. The synergistic effect of Ca2+ with K+ ions improved Cel-3.1 activity significantly (25%) and 1% Polyethylene Glycol (PEG-400), 1% ß-mercaptoethanol enhanced the relative activity Cel-3.1 by 31.68%, 12.03% respectively. Further, the enzymatic (Cel-3.1) hydrolysis of pretreated rice straw and corncob released 13.41 ± 0.26 mg/mL and 15.04 ± 0.08 mg/mL reducing sugars respectively. High Performance Liquid Chromatography (HPLC), Scanning Electron Microscope (SEM), and Fourier Transformation Infrared spectroscopy (FTIR) analysis revealed the capability of Cel-3.1 for the breakdown and hydrolysis of both rice straw and corncob to generate various fermentable sugars.