Extraction of nisin from a 2.5% commercial nisin product using methanol and ethanol solutions.
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Nisin is a class Ia bacteriocin used widely in the food industry to inhibit a number of gram-positive pathogens. Although this peptide exhibits activity against many gram-positive bacteria, its effectiveness can vary significantly depending upon the food application. Encapsulation is one method that has been investigated for improving the activity of nisin. Improvement of the encapsulation efficiency of nisin requires purification of the compound, which can be accomplished utilizing organic solvents. The objective of this study was to use methanol and ethanol solutions to extract and concentrate nisin from a commercial preparation containing 2.5% nisin. Commercial nisin was extracted with different concentrations of ethanol or methanol in sterile water for up to 8 h. Approximately 75% of the nisin activity was recovered with 10 or 50% ethanol compared with less than 1% recovery with an ethanol concentration higher than 90%. Extraction with 10 or 50% methanol was approximately as effective as that with lower concentrations of ethanol. However, yields were significantly greater for extraction with methanol at concentrations greater than 90%. The solubility of the nisin likely influenced the extraction profiles for the conditions used. Purification for an 8-h extraction using 10 and 50% ethanol was 1.36 and 1.93 times, respectively. Purification was less than 0.1 at higher ethanol concentrations due to poor extraction. For methanol treatments, purification factors were all 1.09 to 5.98, and they increased as methanol concentration increased. This method for extracting and purifying nisin from dairy proteins using organic solvents may provide an alternative means for preparing and concentrating nisin for encapsulation and other applications.