Process optimization for gold nanoparticles biosynthesis by Streptomyces albogriseolus using artificial neural network, characterization and antitumor activities

Gold nanoparticles (GNPs) are highly promising in cancer therapy, wound healing, drug delivery, biosensing, and biomedical imaging. Furthermore, GNPs have anti-inflammatory, anti-angiogenic, antioxidants, anti-proliferative and anti-diabetic effects. The present study presents an eco-friendly approach for GNPs biosynthesis using the cell-free supernatant of Streptomyces albogriseolus as a reducing and stabilizing agent. The biosynthesized GNPs have a maximum absorption peak at 540 nm. The TEM images showed that GNPs ranged in size from 5.42 to 13.34 nm and had a spherical shape. GNPs have a negatively charged surface with a Zeta potential of - 24.8 mV. FTIR analysis identified several functional groups including C-H, -OH, C-N, amines and amide groups. The crystalline structure of GNPs was verified by X-ray diffraction and the well-defined and distinct diffraction rings observed by the selected area electron diffraction analysis. To optimize the biosynthesis of GNPs using the cell-free supernatant of S. albogriseolus, 30 experimental runs were conducted using central composite design (CCD). The artificial neural network (ANN) was employed to analyze, validate, and predict GNPs biosynthesis compared to CCD. The maximum experimental yield of GNPs (778.74 μg/mL) was obtained with a cell-free supernatant concentration of 70%, a HAuCl4 concentration of 800 μg/mL, an initial pH of 7, and a 96-h incubation time. The theoretically predicted yields of GNPs by CCD and ANN were 809.89 and 777.32 μg/mL, respectively, which indicates that ANN has stronger prediction potential compared to the CCD. The anticancer activity of GNPs was compared to that of doxorubicin (Dox) in vitro against the HeP-G2 human cancer cell line. The IC50 values of Dox and GNPs-based treatments were 7.26 ± 0.4 and 22.13 ± 1.3 µg/mL, respectively. Interestingly, treatments combining Dox and GNPs together showed an IC50 value of 3.52 ± 0.1 µg/mL, indicating that they targeted cancer cells more efficiently.

NMR characterization of streptogramin B and L-156,587, a non-synergistic pair of the streptogramin family antibiotic complexes produced inductively by a combined culture of Streptomyces albogriseolus and Tsukamurella pulmonis

The complete ¹ H and ¹³ C NMR characterization of streptogramin B (1), the major component of a clinically important synergistic antibiotic complex, was presented for the first time, along with those of L-156,587 (2), a dehydrated congener of streptogramin A (3). Compounds 1 and 2 were not synergistic and produced by Streptomyces albogriseolus in co-culture with Tsukamurella pulmonis, which poses a question on the adaptive significance of the induced production of this antibiotic pair.

Brevibacillus borstelensis and Streptomyces albogriseolus have roles to play in degradation of herbicide, sulfosulfuron

Use of herbicides, in particular sulfosulfuron, at more than recommended doses has raised major concerns about the health hazards for animals and humans. In the present study, isolation of sulfosulfuron-degrading Brevibacillus borstelensis and Streptomyces albogriseolus from the field soils in the northwestern region of India was carried out where the use of sulfosulfuron is predominant, and further assessed for their potential to degrade sulfosulfuron individually and together in a consortium form under lab conditions. Concentration of sulfosulfuron was reduced from 10 to 7.72 µg/ml in 12 h to 5.13 µg/ml in 20 h by B. borstelensis and the metabolites detected by LCMS–MS were aminopyrimidine and a rearranged amine in 12 and 20 h of growth. Similarly, S. albogriseolus reduced the concentration of sulfosulfuron from 10 to 6.74 µg/ml in 12 h to 6.62 µg/ml in 20 h with aminopyrimidine and a rearranged amine as metabolites. B. borstelensis and S. albogriseolus together also reduced the concentration of sulfosulfuron from 10 µg/ml in initial hour to 8.34 µg/ml in 12 h to 6.66 µg/ml in 20 h. Hence, B. borstelensis and S. albogriseolus provide a safer, inexpensive and effective way to bio-remediate the harmful and toxic sulfosulfuron from the environment if further explored at a larger field scale in near future.

Bioprocessing of some agro-industrial residues for endoglucanase production by the new subsp.; Streptomyces albogriseolus subsp. cellulolyticus strain NEAE-J

The use of low cost agro-industrial residues for the production of industrial enzymes is one of the ways to reduce significantly production costs. Cellulase producing actinomycetes were isolated from soil and decayed agricultural wastes. Among them, a potential culture, strain NEAE-J, was selected and identified on the basis of morphological, cultural, physiological and chemotaxonomic properties, together with 16S rDNA sequence. It is proposed that strain NEAE-J should be included in the species Streptomyces albogriseolus as a representative of a novel sub-species, Streptomyces albogriseolus subsp. cellulolyticus strain NEAE-J and sequencing product was deposited in the GenBank database under accession number JN229412. This organism was tested for its ability to produce endoglucanase and release reducing sugars from agro-industrial residues as substrates. Sugarcane bagasse was the most suitable substrate for endoglucanase production. Effects of process variables, namely incubation time, temperature, initial pH and nitrogen source on production of endoglucanase by submerged fermentation using Streptomyces albogriseolus subsp. cellulolyticus have been studied. Accordingly optimum conditions have been determined. Incubation temperature of 30 °C after 6 days, pH of 6.5, 1% sugarcane bagasse as carbon source and peptone as nitrogen source were found to be the optimum for endoglucanase production. Optimization of the process parameters resulted in about 2.6 fold increase in the endoglucanase activity. Therefore, Streptomyces albogriseolus subsp. cellulolyticus coud be potential microorganism for the intended application.