Utilization of chestnut shells: a valuable agronomic waste for bioactive molecules recovery.

For many centuries, chestnut fruits represented one of the most important food resources of rural areas. In recent years, chestnut has become increasingly important because of positive health effects as it is a rich font of bioactive compounds. The peeling process produces a high amount of shells which could be regarded as an exploitable source of high value-added compounds.In fact, they contain huge amounts of phenols provided with antioxidant activity. This residue also contains about 36% sugars in form of polysaccharides. Previously, we investigated the potential of fermentable sugars production from an enzymatic hydrolysate of chestnut shells, but the hydrolysate needs to be detoxified before fermentation because it contains phenolic molecules that inhibits microorganism growth. Currently, the necessity to replace synthetic antioxidants,whose safety has been questioned, has promoted the research of new sources of natural antioxidant molecules. In the present study we have evaluated the efficacy of the phenols removal from the chestnut hydrolysate by activated charcoal, and the successive recovery of the antioxidant molecules from the sorbent. Chestnut shells (5% w/v) were soaked in ammonium hydroxide (10% v/v) at 70°C for 22h, and then subjected to saccharification of the cellulose and xylan fractions for 72h at 50°C, pH 5.0 by enzymatic cocktail prepared with commercial enzymes. The hydrolysate was subjected to detoxification by treatment with untreated charcoal and charcoal heated at 500°C for 1 h. Detoxification with untreated and pretreated charcoal gave similar results with 82% phenol removal. Recovery of the absorbed molecules is at present under assessment through the comparison of different eluents such as water, sodium hydroxide, and alkaline ethanol.