Assessment of lead tolerance in gamma exposed Aspergillus niger van Tieghem & Penicillium cyclopium Westling.

Purpose: Present study deals with the role of gamma irradiation in modulating lead (Pb) tolerance of Aspergillus niger van Tieghem. and Penicillium cyclopium Westling. Materials and methods: After being exposed to gamma absorbed doses those fungal strains were subjected to heavy metal uptake efficacies and anti-oxidative study. Fourier Transform Infrared (FTIR) spectra and Scanning Electron Microscopic (SEM) studies were also evaluated. Result: Gamma exposed A. niger & P. cyclopium showed enhanced growth in terms of colony forming unit (CFU) and more Pb uptake efficacies compared to their un-irradiated counterparts. FTIR spectra illustrated the involvement of functional groups in Pb biosorption. SEM photographs revealed the structural deformities in both the fungal strains after being exposed to Pb and gamma. Upregulated anti-oxidative defense system (super oxide dismutase, catalase, total glutathione) in gamma exposed fungal groups are accountable for enhanced Pb tolerance and removal than that of their un-irradiated counterparts. Conclusion: The outcomes of this study exhibit a light towards a new step of heavy metal bioremediation.

UV Tolerance of Spoilage Microorganisms and Acid-Shocked and Acid-Adapted Escherichia coli in Apple Juice Treated with a Commercial UV Juice-Processing Unit.

The enhanced thermal tolerance and survival responses of Escherichia coli O157:H7 in acid and acidified foods is a major safety concern for the production of low-pH products, including beverages. Little is known about this phenomenon when using UV light treatments. This study was conducted to evaluate the effects of strain (E. coli O157:H7 strains C7927, ATCC 35150, ATCC 43895, and ATCC 43889 and E. coli ATCC 25922) and physiological state (control-unadapted, acid adapted, and acid shocked) on the UV tolerance of E. coli in apple juice treated under conditions stipulated in current U.S. Food and Drug Administration regulations. A greater than 5-log reduction of E. coli was obtained under all tested conditions. A significant effect of strain (P < 0.05) was observed, but the physiological state did not influence pathogen inactivation (P ≥ 0.05). The UV sensitivity of three spoilage microorganisms (Aspergillus niger, Penicillium commune, and Alicyclobacillus acidoterrestris) was also determined at UV doses of 0 to 98 mJ/cm(2). Alicyclobacillus was the most UV sensitive, followed by Penicillium and Aspergillus. Because of the nonsignificant differences in UV sensitivity of E. coli in different physiological states, the use of an unadapted inoculum would be adequate to conduct challenge studies with the commercial UV unit used in this study at a UV dose of 14 mJ/cm(2). The high UV tolerance of spoilage microorganisms supports the need to use a hurdle approach (e.g., coupling of refrigeration, preservatives, and/or other technologies) to extend the shelf life of UV-treated beverages.

Regulation of rubratoxin-B biosynthesis: assessment of role of gamma-irradiation, pH and carbohydrates.

The maximum rubratoxin-B yield was obtained at pH 5.5,, and by increasing the initial pH to near neutrality the yield decreased for both yeast extract sucrose (YES) and Sabouraud dextrose yeast extract (SDYE) media, but the concentration of mycotoxin was higher in YES medium. The rubratoxin-B yield from Penicillium purpurogenium decreased with increasing gamma-irradiation, and at 1.0 kGy no mycotoxin was detected at any pH values. In both the unirradiated and irradiated P. purpurogeniium cultures, as the rubratoxin-B synthesis increased from 46 to 72 h, the lipid content decreased. The concentration (mmoles/g dry wt mycelium) of puridine nucleotides in the mycelium of P. purpurogenium during growth in YES and SDYE media may be a factor in rubratoxin-B synthesis. An elevated NADPH/ NADP ratio favours fatty acid synthesis whereas a depressed NADPH/NADP ratio favours mycotoxin formation. The gamma-irradiation played a role in the regulation of rubratoxin-B biosynthesis.