Volume 49 Number 3

Enzymatic hydrolyses of glucurono(arabino)xylan from two pasture crops, purple guinea (Panicum maximum TD58) and Napier (Pennisetum purpureum ? Pennisetum americanum) grasses

Sorawit Na Nongkhai^a,b,c, Wichanee Bankeeree^b, Hunsa Punnapayak^b, Sehanat Prasongsuk^b, Pongtharin Lotrakul^b,*

 
ABSTRACT:      In this study, purple guinea grass (PG) and Napier grass (NG) were demonstrated and validated as great sources of xylan and, after enzymatic hydrolysis, xylooligosaccharides (XOs) and xylose. A simple alkaline extraction gave near-complete recoveries of xylan from both plants. Based on Response Surface Methodology, the highest xylan yields from PG (95.9?7.6% recovery) and NG (93.5?3.9% recovery) were obtained, respectively, under the following condition: 13.3% (w/v) NaOH, a liquid-to-solid ratio of 13.3:1, 121?C/15 psi, and 44 min; 16.8% (w/v) NaOH, a liquid-to-solid ratio of 14.75:1, 121?C/15 psi, and 30 min. Analyses of sugar composition and FTIR spectra confirmed that xylan from both PG and NG was glucurono(arabino)xylan. These xylans were partially hydrolyzed to obtain XOs using crude endoxylanase while completely hydrolyzed to obtain xylose using a mixture of crude endoxylanase and ?-xylosidase, both from Aureobasidium pullulans. After optimization, the highest yields of both XOs and xylose from PG were significantly enhanced. The yields of reducing sugars (170.3?10.3 mg/g xylan) and combined xylobiose and xylotriose (121.2?1.9 mg/g xylan) were maximized at 74.9 U/g xylan of endoxylanase after 64-h incubation. For xylose, the yield (179.4?3.2 mg/g xylan) was highest at 69.9 U/g xylan and 70.0 U/g xylan of endoxylanase and ?-xylosidase, respectively, after 18-h incubation. Slightly lower yields of reducing sugars (166.4?4.3 mg/g xylan), combined xylobiose and xylotriose (112.2?1.8 mg/g xylan), and xylose (138.8?3.8 mg/g xylan) were obtained from NG.

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* Corresponding author, E-mail: pongtharin.l@chula.ac.th

Received 3 Mar 2025, Accepted 25 Jan 2026