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

Abstract

BACKGROUND: Approximately 0.7 − 1 × 10 6 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 methylesterifiedPFs 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.

Recovery of pectic hydrocolloids and phenolics from huanglongbing related dropped citrus fruit

“…Of the major sugars associated with pectic hydrocolloids (galacturonic acid, rhamnose, arabinose and galactose), only minor amounts of galactose were detected before enzymatic hydrolysis. These findings are in agreement with previous studies . Enzymatic hydrolysis resulted in an increase in glucose and fructose yields resulting from the hydrolysis of cellulose and sucrose.…”

“…The steam‐exploded dropped ‘Hamlin’ fruit was made into a slurry containing cooked fruit tissue (150 g L −1 ) in cold (4 °C) 0.05 mol L −1 trisodium phosphate (TSP) to obtain a pH of ∼12.0 for the alkaline demethylesterification of the released pectic hydrocolloids as described previously . Alternatively, the precipitated pectic hydrocolloids obtained from water washing of the steam‐exploded dropped ‘Hamlin’ fruit were alkaline demethylesterified using sodium hydroxide as described previously …”

Process–Structure–Function Relations of Pectin in Food

“…(Rolin 2002). In search for an improved extraction in terms of yield, extraction time and/or quality of the obtained products, different alternatives have been investigated including the application of ultrasound (Panchev et al 1994), microwave heating (under pressure) (Fishman et al 2000) and steam treatment (Fishman et al 2003;Grohmann et al 2012). Finally, the application of enzymes presents a more environmentally friendly way for the extraction of pectin.…”

Production of pectinases by solid-state fermentation of a mixture of citrus waste and sugarcane bagasse in a pilot-scale packed-bed bioreactor

“…[1]). Currently, citrus pulp is either dumped, or given away or sold with a very small margin to be used as a complement for cattle feed [2]. However, citrus waste biorefineries could be established to produce pectin [3], limonene [3][4][5], ethanol [3][4][5] and d-galacturonic acid as a platform chemical [6,7].…”