Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 9, 2005
Publication Date: February 28, 2006
Repository URL: http://www.ars.usda.gov/sp2UserFiles/Place/66210000/Reprint967.pdf
Citation: Cameron, R.G., Luzio, G.A., Baldwin, E.A., Narciso, J.A., Plotto, A. 2006. Production of narrow-range size-classes of polygalacturonic acid oligomers. Proceedings of Florida State Horticultural Society. 118:406-409. Interpretive Summary: Pectin, a major component of citrus fruit peel, is composed largely of polygalacturonic acid (PGA). Potential uses for PGA, modified PGA or PGA containing bio-based products include additives for a variety of manufactured products, ion exchange resins, flavor or aroma encapsulators, as coatings or surface treatments and as substrates for studying how pectin degrading enzymes function. The functional properties of PGA largely depend on its size. Small changes in polymer length can produce very different functional properties. One method of changing its structural properties is by enzymatic degradation. In this report we used an endo-polygalacturonase enzyme and differential precipitation methods to produce three different narrow-range size-classes of PGA. These size-classes will be used to study how different pectin degrading enzymes function, their efficiency in binding specific pollutants and their ability to delay decay in minimally processed fruits.
Technical Abstract: A structural component of citrus processing residues with significant functionality is the homogalacturonan region of pectin. Its functional properties include ion binding, gelation, water retention and elicitation of plant defense responses to pathogens. It is also the site of attack by commercial pectinolytic enzymes used as processing aids for viscosity reduction, enzymatic peeling and conversion of peel polysaccharides to monomeric sugars for subsequent fermentation. More recently endo-polygalacturonases (EPG) have been used as research tools to probe the mode of action of pectin methylesterases and to map pectin fine structure. Consequently, knowing how EPG acts on oligomers of polygalacturonic acid is needed. A major limitation in studying these oligomers has been the difficulties due to limitations on chromatographic detection. In the work presented here, three size-classes with a degree of polymerization ranging from 1-13, 8-24 and 22-46 were prepared by enzymatic digestion followed by a combination of differential pH and alcohol precipitation. The oligomers were characterized using improved chromatographic techniques that enabled us to estimate masses of individual oligomers. Strawberries were treated with each size-class to determine if the fragments elicited a biological response. The medium-DP size-class resulted in a delay in fruit decay not observed with the low- or high-DP size-classes.