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ABSTRACT: A sodium hydroxide-induced process was adopted and the effects of NaOH concentration, liquid-tosolid ratio, temperature, and stirring time on xylan extraction were investigated. Response surface methodology (RSM) was employed to optimize the selected conditions for xylan extraction. The results showed that NaOH concentration (w/w, %), liquid-to-solid ratio (mL/g,) and stirring time significantly affected the total xylan yield (TXY). The optimum conditions for xylan extraction were: NaOH concentration of 2.23%, liquid-to-solid ratio of 32.11 mL/g, temperature of 93°C, and stirring time of 1.8 h. Under these conditions, TXY of 46.94% was obtained. In addition, soluble xylan (WXY) had a higher inhibitory effect on apple (polyphenoloxidases) PPO activity than did insoluble xylan yield (WIXY) and TXY.
KEY WORDS: Corn straw xylan, PPO inhibition, Response surface methodology, Sodium hydroxide
INTRODUCTION
In China, millions of tons of corn straws are produced each year that are disposed by burning or leaving unused, which causes environmental pollution and wastes resources (Cherubini, 2010; Dale, 2003). Therefore, how to utilize corn straws efficiently has become a focus for research (Sermanni et al., 1994; Yang et al., 2001). Corn straws are rich in structural carbohydrates such as celluloses, hemicelluloses and xylans (Ebringerova and Heinze, 2000). Xylan, an important renewable biopolymer resource, is composed of a β-1,4xylosidic chain backbone with different side chains of xylose, arabinose, glucuronic acids, and acetyl acids. Corn straw contains considerable amounts of xylan-rich hemicelluloses that include soluble xylan (WXY) and insoluble xylan (WIXY), differing in composition and structural features (Ebringerova et al., 1992; Ebringerová et al., 2002). Sodium hydroxide has been shown as a suitable alkali for xylan extraction from corn straws (Ebringerova and Heinze, 2000; Huang et al., 2015). This manuscript presents data describing conditions for efficient extraction of xylan from corn straw.
Corn straw xylan has potential for practical application as an available form of bioenergy (Ragauskas et al., 2006; Wanner et al., 2005). Research findings indicate that xylan can be used as an additive in food preservation, food nutrition, and food technology (Moure et al., 2006; Sedlmeyer, 2011). For example, xylan can be co-heated with chitosan to prepare a food preservative (Li et al., 2011). Polyphenoloxidases (EC 1.10.3.1, PPO) negatively affect the appearance of vegetables and fruit. Evidence shows that apple browning is closely...