The current investigation addressed the green synthesis of silver nanoparticles (AgNPs) using newly isolated silver-resistant rare actinomycetes, Glutamicibacter nicotianae SNPRA1 and Leucobacter aridicollis SNPRA2, and investigated their impact on the mycotoxigenic fungi Aspergillus flavus ATCC 11498 and Aspergillus ochraceus ATCC 60532. The formation of AgNPs was evidenced by the reaction’s color change to brownish and the appearance of the characteristic surface plasmon resonance. The transmission electron microscopy of biogenic AgNPs produced by G. nicotianae SNPRA1 and L. aridicollis SNPRA2 (designated Gn-AgNPs and La-AgNPs, respectively) revealed the generation of monodispersed spherical nanoparticles with average sizes of 8.48 ± 1.72 nm and 9.67 ± 2.64 nm, respectively. Furthermore, the XRD patterns reflected their crystallinity and the FTIR spectra demonstrated the presence of proteins as capping agents. Both bioinspired AgNPs exhibited a remarkable inhibitory effect on the conidial germination of the investigated mycotoxigenic fungi. The bioinspired AgNPs caused an increase in DNA and protein leakage, suggesting the disruption of membrane permeability and integrity. Interestingly, the biogenic AgNPs completely inhibited the production of total aflatoxins and ochratoxin A at concentrations less than 8 μg/mL. At the same time, cytotoxicity investigations revealed the low toxicity of the biogenic AgNPs against the human skin fibroblast (HSF) cell line. Both biogenic AgNPs exhibited feasible biocompatibility with HSF cells at concentrations up to 10 μg/mL and their IC₅₀ values were 31.78 and 25.83 μg/mL for Gn-AgNPs and La-AgNPs, respectively. The present work sheds light on the antifungal prospect of the biogenic AgNPs produced by rare actinomycetes against mycotoxigenic fungi as promising candidates to combat mycotoxin formation in food chains at nontoxic doses.

: This study compared microbiological and chemical methods used in astaxanthin extraction from the exoskeleton of the shrimp species Penaeus japonicus and Penaeus semisulcatus. The microbiological method was performed using Saccharomyces cerevisiae (bakery yeast) or Lactobacillus acidophilus (from yogurt), followed by solvent extraction with hexane and acetone at different ratios (1:1, 1:2, and 1:3). The chemical method was performed traditionally using hexane. The highest astaxanthin yield from P. japonicus exoskeleton was obtained using either S. cerevisiae or L. acidophilus followed by solvent extraction with hexane and acetone at a ratio of 1:1 (8.5 and 8.1 mg/g waste, respectively) as well as by the chemical method (8.4 mg/g waste). Likewise, the highest astaxanthin yield from P. semisulcatus exoskeleton was obtained using either S. cerevisiae or L. acidophilus followed by solvent extraction with hexane and acetone at a ratio of 1:1 (3.0 and 4.1 mg/g waste, respectively) as well as by the chemical method (3.2 mg/g waste). The values obtained from P. semisulcatus exoskeleton were considerably lower than those attained from P. japonicus exoskeleton. In addition, the nuclear magnetic resonance (C-NMR) analysis confirmed that astaxanthin was the main carotenoid present in the extract. In conclusion, the pretreatment of exoskeleton wastes of P. japonicus using S. cerevisiae followed by solvent extraction with hexane and acetone at a ratio of 1:1 as well as the classical chemical treatment led to the highest astaxanthin content.

Astaxanthin is a xanthophyll carotenoid possessing impressive nutraceutical, antioxidant, and bioactive merits. Traditionally, astaxanthin is extracted from crustacean wastes via solvent extraction methods. However, the rigid structure of shells that comprise complex proteins and chitin challenges the extraction process. This investigation addressed an efficient microbial-assisted method to facilitate astaxanthin recovery from crab exoskeleton waste utilizing chitinolytic and proteolytic microorganisms. Herein, we evaluated the effect of pretreatment of the exoskeleton waste with a newly isolated probiotic strain, Bacillus amyloliquefaciens CPFD8, showing remarkable protease and chitinase activity and a proteolytic Saccharomyces cerevisiae 006-001 before solvent extraction, using acetone/hexane, on astaxanthin recovery. Furthermore, the antioxidant and anti-inflammatory activities of the recovered astaxanthin were inspected. Results revealed that both strains boosted the astaxanthin yield from the crab (Callinectes sapidus) exoskeleton compared with solvent extraction using acetone/hexane. Under optimum conditions, astaxanthin yield was 217 and 91 µg/g crab exoskeleton in samples treated with B. amyloliquefaciens CPFD8 and S. cerevisiae 006-001, respectively. Interestingly, pretreatment of crab exoskeleton waste with B. amyloliquefaciens CPFD8 yielded more than 6-fold astaxanthin compared with the solvent extraction method that yielded just 35 µg/g. This increase could be attributed to the proteolytic activity of B. amyloliquefaciens CPFD8 that rendered deproteinized shell chitin accessible to chitinase, facilitating the penetration of solvents and the recovery of astaxanthin. The recovered astaxanthin exhibited excellent antioxidant activity in scavenging DPPH or ABTS free radicals with IC₅₀ values of 50.93 and 17.56 µg/mL, respectively. In addition, the recovered astaxanthin showed a remarkable anti-inflammatory impact on LPS-induced murine macrophage RAW264.7 cells and significantly inhibited the production of nitric oxide, TNF-α, and IL-6 compared with the untreated control. These findings suggest the potential use of the developed microbial-assisted method utilizing chitinolytic and proteolytic B. amyloliquefaciens CPFD8 to maximize the recovery of bioactive astaxanthin from crab (C. sapidus) exoskeleton waste.