(599bh) Production of Xylooligosaccharides from Beechwood Xylan and Sawdust By Using Clostridium Sp. BOH3 Xylanase

Authors: 
Yang, K. L., National University of Singapore
Rajagopalan, G., National University of Singapore (NUS)
Shanmugavelu, K., National University of Singapore
Hong Wei, L., National University of Singapore

Abstract

Xylooligosaccharides (XOS) are oligomers of xylose and often used as additives in food, animal feeds, and drugs. In the literature, there are many methods for production of XOS. Among them, enzymatic hydrolysis of xylan is very popular due to its mild reaction conditions. Recently, a new isolate Clostridium sp. BOH3 is reported to express endo-xylanase from reinforced clostridial medium supplemented with xylan (1%w/v). BOH3 xylanase can be purified by using FPLC with an anionic Q-column. In this study, XOS production from beechwood xylan by using free and immobilized BOH3 xylanase is investigated. We also study the possibility of utilizing low-cost substrates including mango, teak and mahogany sawdusts. Our results show that BOH3 xylanase can hydrolyse beechwood xylan (5%w/v) and release XOS mixtures which contain 33.7 % of xylobiose (X2), 32.2 % of xylotriose (X3), 22.4 % of xylotetraose (X4), 4.5 % of xylopentaose (X5) and negligible amount (0.34%) of xylose. To recycle BOH3 xylanase after hydrolysis, the enzyme is immobilized in calcium alginate beads. Alignate beads prepared by using 4-5% of calcium alginate are stable for 3 successful runs, and their mechanical strength can be further enhanced by adding 1-3% of silica gel. Interestingly, immobilized xylanase only produces X2 (45%), X3 (43%) and xylose (<5%) after 24h of hydrolysis. Moreover, sawdusts from a wide variety of hardwoods including mahogany, teak and mango were employed as substrates to replace xylan for XOS production. Among the selected substrates, mahogany sawdust can be used to produce 25.45±0.25mg/g of XOS. After optimization, 32±1.2mg/g of XOS can be produced from mahogany sawdust pretreated with 0.05N of NaOH. Our results support that mahogany sawdust can be used as low-cost substrate for XOS production. This study is potentially useful for production of XOS for commercial and industrial use.

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