Extraction and recovery of pectic fragments from citrus processing waste for co–production with ethanol


Correspondence to: Randall Cameron, USDA, ARS, Citrus and Subtropical Products Research Unit, U.S. Horticultural Research Laboratory, 2001 South Rock Road, Ft. Pierce, FL, USA. E-mail: Randall.cameron@ars.usda.gov


BACKGROUND: Approximately 0.7 − 1 × 106 dry tons of citrus processing waste (CPW) are produced annually in the United States. CPW is sold as animal feed but often the financial return does not exceed the production cost. Polysaccharides comprise 40% of the total dry matter of which pectin is the major component. CPW was steam treated to extract pectin fragments (PFs) as a value added co–product prior to fermentation of other sugars for biofuels production.

RESULTS: PFs were extracted in high yields, along with polymeric arabinans, galactans and arabinogalactans. The extracted polysaccharides ranged in size from small oligomers to polymers of ∼700 000 g mol−1. Acidified treatments led to greater fragmentation of water soluble polysaccharides, but did not enhance fragmentation of pectins to small oligomers (> 30 mer). Methylesterified PFs, arabinans and galactans were recovered by ethanol precipitation while demethylesterified PFs were recovered and purified by precipitation with dilute HCl.

CONCLUSION: Steam treatment of CPW provides for rapid, efficient fragmentation of protopectin into highly methylesterified PFs that could be recovered by precipitation. The steaming process for preparation of PFs is environmentally friendly. No toxic chemicals are introduced and the remaining CPW can be used in fermentations to produce ethanol and other compounds. © 2012 Society of Chemical Industry