The PEOVW concentration used in this study was determined by investigating the inhibitory effects on E. coli K-12 strain 14R525 for a range of concentrations from 0.75 mg ml−1 to 12 mg ml−1. E. coli K-12 was cultured in LB and grown at 37°C. The MIC and growth kinetics were evaluated by measuring the optical density (JASCO 7800 UV/VIS Spectrophotometer) after 24 h and adjusting for interference by PEOVW pigments. Inhibition (%) = {[ODE. coli − (ODE. coli+PEOVW − ODPEOVW)]/ODE. coli} × 100, where ODE. coli is the OD600 for the negative control (containing no PEOVW), ODE. coli+VWPE is the OD600 for the sample treated with PEOVW and ODPEOVW is the OD600 for PEOVW. The MBC (minimum bactericidal concentration) and the counts on plates after 24 h were defined. The experiments were performed in triplicate. As PEOVW was diluted in 20% ethanol, the potential effects of this solvent on E. coli K-12 growth were also evaluated.
7800 uv vis spectrophotometer
Manufactured by Jasco
Sourced in United States
The 7800 UV/VIS Spectrophotometer is a laboratory instrument designed to measure the absorbance or transmittance of light in the ultraviolet and visible regions of the electromagnetic spectrum. It is capable of detecting and quantifying various compounds and materials by analyzing their interaction with light.
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2 protocols using 7800 uv vis spectrophotometer
1
PEOVW Antibacterial Activity on E. coli
2
Quantifying Milk Protein Hydrolysis
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The experimental set-up made it possible to calculate the net proteolytic activity produced during 2 weeks of storage at 37°C after a heat treatment simulating UHT process and storage (as described in Marchand et al., 2008 , 2009a ). Hydrolysis of proteins was measured by the determination of the release of a-amino groups by the trinitrobenzenesulfonic acid (TNBS) method. The free amino groups react with the TNBS reagent (Sigma-Aldrich) at pH 9.2 in the dark. A yellow-orange colour develops and its intensity is determined by absorption measurements at 420 nm. The degree of proteolysis is calculated from the increase in absorption after 2 weeks of storage at 37°C and expressed as mmol of glycine equivalents mL-1 milk, using glycine (2.5, 2.25, 2, 1.75, 1.5, 1.25, 1, 0.75, 0.5, 0.25 e 0 mM; Sigma-Aldrich) to create a standard curve. The experiment was repeated twice, first in macro method (experiment A using a 7800 UV/VIS spectrophotometer; JASCO, Easton, MD, USA) and second time in micro method (experiment B using a Multiskan GO UV/Vis spectrophotometer (Thermo Fisher Scientific).
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