In this present study, a newly isolated strain, Streptomyces sp. NEAE-H, capable of producing high amount of black extracellular melanin pigment on peptone-yeast extract iron agar and identified as Streptomyces glaucescens NEAE-H. Plackett–Burman statistical design was conducted for initial screening of 17 independent (assigned) variables for their significances on melanin pigment production by Streptomyces glaucescens NEAE-H. The most significant factors affecting melanin production are incubation period, protease-peptone and ferric ammonium citrate. The levels of these significant variables and their interaction effects were optimized by using face-centered central composite design. The maximum melanin production (31.650 μg/0.1 ml) and tyrosinase activity (6089.10 U/ml) were achieved in the central point runs under the conditions of incubation period (6 days), protease-peptone (5 g/L) and ferric ammonium citrate (0.5 g/L). Melanin pigment was recovered by acid-treatment. Higher absorption of the purified melanin pigment was observed in the UV region at 250 nm. It appeared to have defined small spheres by scanning electron microscopy imaging. The maximum melanin yield was 350 mg dry wt/L of production medium. In vitro anticancer activity of melanin pigment was assayed against skin cancer cell line using MTT assay. The IC ₅₀ value was 16.34 ± 1.31 μg/ml for melanin and 8.8 ± 0.5 μg/ml for standard 5-fluorouracil.

In recent decades, researchers were attracted towards cyanobacterial components which are potential low-cost biological reagents for silver nanoparticle biosynthesis. This article describes the biological synthesis of silver nanoparticles using a proteinaceous pigment phycocyanin extracted fromNostoc linckiaas reducing agent. The synthesized silver nanoparticles have a surface plasmon resonance band centered at 425 nm. Face-centered central composite design used for optimization of silver nanoparticles (AgNPs) biosynthesis using phycocyanin. The maximum AgNPs biosynthesis obtained using the optimized four variables, initial pH level (10), AgNO₃concentration (5 mM), phycocyanin pigment concentration (1 mg/mL) and incubation period (24 h) was 1100.025 µg/mL. The TEM analysis of AgNPs showed spherical nanoparticles with mean size between 9.39 to 25.89 nm. FTIR spectra showed major peaks of proteins involved in AgNPs biosynthesis by identifying different functional groups involved in effective capping of AgNPs. The biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic Gram-positive (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa, E. coliandKlebsiella pneumonia). The synthesized AgNPs exhibited effective cytotoxic activity against MCF-7 and the inhibitory concentration (IC₅₀) was recorded at 27.79 ± 2.3 µg/mL. Thein vivostudies clearly indicated that AgNPs has a capacity to inhibit the growth of tumor in Ehrlich ascites carcinoma bearing mice.

Chlorella vulgaris, like a wide range of other microalgae, are able to grow mixotrophically. This maximizes its growth and production of polysaccharides (PS). The extracted polysaccharides have a complex monosaccharide composition (fructose, maltose, lactose and glucose), sulphate (210.65 ± 10.5 mg g⁻¹ PS), uronic acids (171.97 ± 5.7 mg g⁻¹ PS), total protein content (32.99 ± 2.1 mg g⁻¹ PS), and total carbohydrate (495.44 ± 8.4 mg g⁻¹ PS). Fourier Transform infrared spectroscopy (FT-IR) analysis of the extracted polysaccharides showed the presence of N–H, O–H, C–H, –CH₃, >CH₂, COO⁻¹, S=O and the C=O functional groups. UV–Visible spectral analysis shows the presence of proteins, nucleic acids and chemical groups (ester, carbonyl, carboxyl and amine). Purified polysaccharides were light green in color and in a form of odorless powder. It was soluble in water but insoluble in other organic solvents. Thermogravimetric analysis demonstrates that Chlorella vulgaris soluble polysaccharide is thermostable until 240°C and degradation occurs in three distinct phases. Differential scanning calorimetry (DSC) analysis showed the characteristic exothermic transition of Chlorella vulgaris soluble polysaccharides with crystallization temperature peaks at 144.1°C, 162.3°C and 227.7°C. The X–ray diffractogram illustrated the semicrystalline nature of these polysaccharides. Silver nanoparticles (AgNPs) had been biosynthesized using a solution of Chlorella vulgaris soluble polysaccharides. The pale green color solution of soluble polysaccharides was turned brown when it was incubated for 24 hours with 100 mM silver nitrate in the dark, it showed peak maximum located at 430 nm. FT-IR analysis for the biosynthesized AgNPs reported the presence of carbonyl, –CH₃, >CH₂, C–H,–OH and –NH functional groups. Scanning and transmission electron microscopy show that AgNPs have spherical shape with an average particle size of 5.76. Energy-dispersive X-ray (EDX) analysis showed the dominance of silver. The biosynthesized silver nanoparticles were tested for its antimicrobial activity and have positive effects against Bacillus sp., Erwinia sp., Candida sp. Priming seeds of Triticum vulgare and Phaseolus vulgaris with polysaccharides solutions (3 and 5 mg mL⁻¹) resulted in significant enhancement of seedling growth. Increased root length, leaf area, shoot length, photosynthetic pigments, protein content, carbohydrate content, fresh and dry biomass were observed, in addition these growth increments may be attributed to the increase of antioxidant activities.

Chitosan nanoparticles (CNPs) are promising versatile cationic polymeric nanoparticles, which have received growing interest over last few decades. The biocompatibility, biodegradability, environmental safety and non-toxicity of the chitosan nanoparticles makes it preferred for a wide range of biological applications including agriculture, medical and pharmaceutical fields. In this study, CNPs were biosynthesized by aqueous extract of Eucalyptusglobulus Labill fresh leaves as bio-reductant. Box–Behnken design in 29 experimental runs was used for optimization of different factors affecting the production of CNPs. The maximum yield of CNPs was 9.91 mg/mL at pH of 4.5, chitosan concentration of 1%, incubation time of 60 min and temperature of 50 °C. The crystallinity, particle size and morphology of the biosynthesized CNPs were characterized. The CNPs possess a positively charged surface of 31.1 mV. The SEM images of the CNPs confirms the formation of spherical form with smooth surface. The TEM images show CNPs were spherical in shape and their size range was between 6.92 and 10.10 nm. X-ray diffraction indicates the high degree of CNPs crystallinity. FTIR analysis revealed various functional groups of organic compounds including NH, NH₂, C–H, C−O, C–N, O–H, C–C, C–OH and C–O–C. The thermogravimetric analysis results revealed that CNPs are thermally stable. The antibacterial activity of CNPs was determined against pathogenic multidrug-resistant bacteria, Acinetobacterbaumannii. The diameters of the inhibition zones were 12, 16 and 30 mm using the concentrations of 12.5, 25 and 50 mg/mL; respectively. When compared to previous studies, the biosynthesized CNPs produced using an aqueous extract of fresh Eucalyptusglobulus Labill leaves have the smallest particle sizes (with a size range between 6.92 and 10.10 nm). Consequently, it is a promising candidate for a diverse range of medical applications and pharmaceutical industries.

Phycoerythrin is the main phycobiliprotein that responsible for harvesting light for photosynthesis in cyanobacteria. In this research, phycoerythrin extracted from the cyanobacteriumNostoc carneumhas been used to reduce silver nitrate for silver nanoparticles (AgNPs) biosynthesis. UV–visible spectrophotometry for measuring surface plasmon resonance showed a single absorption peak at 430 nm, which confirmed the presence of AgNPs. The face-centered central composite design was chosen to evaluate the interaction effects between four process variables and also to determine their optimal levels which influence the AgNPs biosynthesis using phycoerythrin. The maximum silver nanoparticles biosynthesis (1733.260 ± 21 µg/mL) was achieved in the central runs under the conditions of initial pH 10, incubation period of the 24 h, phycoerythrin concentration of the 0.8 mg/mL and 20 mM of AgNO₃. The biosynthesized AgNPs were characterized using TEM which revealed the formation of spherical shape nanoparticles with size ranged between 7.1‒26.68 nm. EDX analysis confirmed silver as the major constituent element. FTIR spectrum indicates the presence of proteinaceous capping agent that prevents silver nanoparticles agglomeration. The IC₅₀of cell inhibition by AgNPs was observed at 13.07 ± 1.1 µg/mL. Treatment of mice bearing Ehrlich ascites carcinoma with 5 mg AgNPs/kg of mice body weight significantly decreased tumor volume, tumor cells count, white blood cells count and body weight. It was concluded that the phycoerythrin protein has the ability to synthesize AgNPs, which have antibacterial, antihemolytic,in vitroandin vivocytotoxic activities.

L-asparaginase is an important enzyme as therapeutic agents used in combination with other drugs in the treatment of acute lymphoblastic leukemia. A newly isolated actinomycetes strain, Streptomyces sp. NEAE-82, was potentially producing extracellular L-asparaginase, it was identified as Streptomyces fradiae NEAE-82, sequencing product was deposited in the GenBank database under accession number KJ467538. L-asparaginase was purified from the crude enzyme using ammonium sulfate precipitation, dialysis and ion exchange chromatography using DEAE Sepharose CL-6B. Further the kinetic studies of purified enzyme were carried out. The optimum pH, temperature and incubation time for maximum L-asparaginase activity were found to be 8.5, 40 °C and 30 min, respectively. The optimum substrate concentration was found to be 0.06 M. The Km and Vmax of the enzyme were 0.01007 M and 95.08 Uml⁻¹min⁻¹, respectively. The half-life time (T_1/2) was 184.91 min at 50 °С, while being 179.53 min at 60 °С. The molecular weight of the subunits of L-asparaginase was found to be approximately 53 kDa by SDS–PAGE analysis. The purified L-asparaginase showed a final specific activity of 30.636 U/mg protein and was purified 3.338-fold. The present work for the first time reported more information in the production, purification and characterization of L-asparaginase produced by newly isolated actinomycetes Streptomyces fradiae NEAE-82.