Abstract
Xylanases are hydrolases which depolymerize the xylan components present in plants cell wall. Commercial applications for these enzymes include its use in the pulp bleaching, food and animal feed industries, among others. Recently, there is a great interest on the exploitation of agro-industrial wastes as low-cost raw materials for value-added compounds production, as xylanolytic enzymes for industrial applications. This is the first report about the xylanase production using pineapple peel as substrate. The xylanase production by Trichoderma viride was optimized and the enzymes produced were biochemically characterized. Additionally, the effect of these enzymes on pulp biobleaching process was evaluated. High xylanase production was obtained with pineapple peel at 2% concentration, for seven days, in stationary cultivation at 28°C, in pH 7.5. Xylanases were more active at 50°C, pH 6.0-6.5 remaining stable at pH 5.0-5.5. T. viride xylanase was stable at 40°C, showing the half-life (T 1/2 ) value of 255 min. The enzyme was remarkably stimulated by Mg 2+ and Zn 2+ , while Pb 3+ and Hg 2+ were strong inhibitors of the xylanase activity. This work shows the ability of the filamentous fungus T. viride to produce high levels of xylanases using pineapple peel as substrate, an inexpensive and abundant agro-industrial waste. Therefore, the reduction on kappa number achieved in this investigation revealed the application potential of these enzymes in biobleaching process. Keywords: Agro-industrial wastes, filamentous fungi, submerged fermentation, pulp pretreatment, xylanolytic enzymes African Journal of Biotechnology, Vol 13(22) 2248-2259
Highlights
After cellulose, xylan is the most abundant polysaccharide present in wood, agricultural and several agroindustrial wastes
Submerged fermentation was prepared in 125 ml flasks containing 25 ml of the Vogel’s medium, pH 6.5, supplemented with 1% carbon source and inoculated with 1.0 ml conidia suspension (7 × 107 conidia/mL) to each flask
Only cellulose production using pineapple peel as substrate was described in the literature (Folakemi et al, 2008; Saravanan et al, 2013)
Summary
Xylan is the most abundant polysaccharide present in wood, agricultural and several agroindustrial wastes This complex heteropolysaccharide consists of a main chain of 1,4-β-D-xylose monomers which is partially acetylated and substituted in different degrees by a variety of side chains, mainly single α-Dglucuronosyl and α-L-arabinosyl units (Collins et al., 2005; Wakiyama et al, 2008). The main enzymes involved in xylan degradation are the endo-β-(1,4)-xylanases. An example is the bioconversion of lignocellulosic residues in their constituent sugars These enzymes have attracted attention due to their role in the production of xylose which can be converted into bioethanol and xylitol (Laxmi et al, 2008)
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