Two-step hydrolysis of nipa (Nypa fruticans) frond as treated by semi-flow hot-compressed water

Abstract

Two-step hydrolysis of nipa (Nypa fruticans) frond, one of the monocotyledonous angiosperms, was studied in a semi-flow hot-compressed water treatment at 230°C/10 MPa/15 min (first stage) and 270°C/10 MPa/30 min (second stage). In the first stage, hemicelluloses such as O-acetyl-4-O-methylglucuronoarabinoxylan and pectin and para-crystalline cellulose were selectively hydrolyzed, as well as lignin, which was partially decomposed. In the second stage, hydrolysis of crystalline cellulose and some additional decomposition of lignin were observed. In addition, inorganic constituents and free sugars, composed mainly of glucose, fructose, and sucrose, were recovered in cold water (20°C/10 MPa/30 min) prior to these 2 stages. In total, 97.3% of oven-dried nipa frond sample could be solubilized into cold and hot-compressed water. The degradation products in the water-soluble portion were primarily recovered as various saccharides (hydrolyzed moieties of the polyoses), which were later dehydrated, fragmented and isomerized partly. The residual (2.7%) is composed mainly of lignin associated with 0.4% of Si. A decomposition pathway is proposed for O-acetyl-4-O-methylglucuronoarabinoxylan as the major hemicellulose based on its various hydrolyzed products.

Two-step hydrolysis of rice (Oryza sativa) husk as treated by semi-flow hot-compressed water

“…Arabinan units are hydrolyzed and recovered as arabinose obviously faster than other mono-saccharides. Similar results were also observed in our previous studies (Lu et al, 2009;Ogura et al, 2013;Phaiboonsilpa et al, 2011Phaiboonsilpa et al, , 2010. The relatively high susceptibility of arabinose in wood hemicelluloses to acid hydrolysis is well known (Fengel and Wegener, 1984;Rydholm, 1965;Sano et al, 1989).…”

“…In rice straw (Ogura et al, 2013), however, larger amounts of free sugars (0.03%) and inorganic constituents (2.8%) were found in the cold-water extracts. This recovery was more pronounced in the study of nipa frond (Phaiboonsilpa et al, 2011). It was reported that 1.5% of free sugars and 7.4% of inorganic constituents could be achieved.…”

“…In brief, approximately 0.5 g of oven-dried rice husk sample was placed into the reaction vessel and treated with cold water (20°C/10MPa/30min) in the semi-flow manner, followed by two-step semi-flow hot-compressed water at 1 st stage, 230°C/10MPa/15min, and 2 nd stage, 270°C/10MPa/30min. The same fractionation process as our previous works was applied to the rice husk (Phaiboonsilpa et al, 2011). Solubles in cold and hot-compressed water were collected by the fraction collector every 1 min.…”

“…In our previous works (Lu et al, 2009;Ogura et al, 2013;Phaiboonsilpa et al, 2011Phaiboonsilpa et al, , 2010), a two-step hydrolysis of various lignocelluloses has been reported, in the course of which the samples are treated in a semi-flow system with hot-compressed water. Four lignocellulose samples from taxonomically different plant species have been studied, i.e., 1Japanese cedar (Cryptomeria japonica) as one of the softwoods, gymnosperms, 2Japanese beech (Fagus crenata) as one of the hardwoods, dicotyledonous angiosperms, 3frond of nipa (Nypa fruticans) as one of the palms (Arecaceae), monocotyledonous angiosperms, and (4) straw of rice, as one of the grasses (Gramineae), monocotyledonous angiosperms.…”

Hydrothermal processing, as an alternative for upgrading agriculture residues and marine biomass according to the biorefinery concept: A review

“…3B). The residence time of liquid products is short, compared to a batch reactor [16,82,[93][94][95][96][97][98]. Liu and Wyman [99] reported that in this type of reactors the fluid velocity in flow through has a significant impact on hydrothermal processing.…”