Abstract
An alkaline xylanase secreted by Paenibacillus macquariensis RC 1819 has been purified using ammonium sulfate fractionation, ion exchange chromatography using DEAE-cellulose and gel filtration chromatography over Sephadex G-200 and Sephadex G-100. The purified enzyme had the specific activity, 25.2 units/mg protein with birchwood xylan as a substrate. The purified enzyme showed a single protein band over sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of the enzyme has been found to be 31,000 ± 2000 as determined by using Sephadex G-200 gel filtration chromatography. The subunit molecular weight has also been found to be ~31,000 as determined using SDS-PAGE indicating monomeric enzyme. The enzyme showed optimum activity at pH 8.6 and temperature, 50°C. The Michaelis constant (Km) of the enzyme for birchwood xylan was 2.2 mg/ml as determined using velocity saturation plot. The metal ions viz. Co+2 and Mn+2 stimulated xylanase enzyme activity whereas Hg+2 inhibited the enzyme activity.
Highlights
Hemicellulose is the second most abundant component in plant cell wall and xylan is the major component of hemicellulose which is found in solid agricultural and agroindustrial residues, as well as in effluents released during wood processing [1,2]
An alkaline xylanase secreted by Paenibacillus macquariensis RC 1819 has been purified using ammonium sulfate fractionation, ion exchange chromatography using DEAE-cellulose and gel filtration chromatography over Sephadex G-200 and Sephadex G-100
The ion exchange chromatography over DEAE-cellulose of the 30% to 60% ammonium sulfate fraction revealed only one peak of xylanase activity that was eluted at 0.22 M NaCl (Figure 1)
Summary
Hemicellulose is the second most abundant component in plant cell wall and xylan is the major component of hemicellulose which is found in solid agricultural and agroindustrial residues, as well as in effluents released during wood processing [1,2]. A 20% - 35% of the total dry weight of plants accounts for xylans which can be used for production of fermentable sugars and fuels [4,5]. Xylanase is produced by many bacteria and fungi [6,7]. It has been exploited for a range of industrial and environmental applications. A recent application of xylanase is in the production of biofuels. It is estimated that the total energy content of global xylan and cellulose waste is equivalent to almost 640 billion tons of oil [10]
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