![]() ![]() The partial 16S rRNA sequences were retrieved on NCBI server ( ) using BLAST tool. Culture was deposited at National Centre for Cell Sciences (NCCS), Pune, India. Prominent selected isolate was identified on the basis of morphological, cultural, biochemical properties and 16S rRNA sequencing. Twenty five bacterial cultures were screened for xylanolytic ability by adding dye-labelled substrate, for example, xylan-brilliant red 3BA in xylan agar medium. Enrichment was done using birchwood xylan (Sigma Chemicals, Germany) as a sole source of carbon. Soil samples were collected from coastal areas of Mandovi, Goa, India. In addition, this xylanase was found to be able to degrade xylan into xylo-oligosaccharides. To our knowledge, this is the first report describing the production of thermoalkalophilic cellulase-free xylanase by Bacillus arseniciselenatis DSM 15340. In consideration with these facts the present study aims to characterize extracellular alkalothermophilic xylanase produced by Bacillus arseniciselenatis DSM 15340 when grown in solid state fermentation. The technique of fermentation using solid state substrate has the great advantage over submerged fermentation due to absence or near absence of aqueous phase that provides natural habitat for growth of microorganisms, economy of the space, simplicity of the media, no complex machinery, equipments and control systems, greater compactness of the fermentation vessel owing to a lower water volume, greater product yields, reduced energy demand, lower capital and recurring expenditures in industry, easier scale-up of processes, lesser volume of solvent needed for product recovery, superior yields, absence of foam build-up, and easier control of contamination due to the low moisture level in the system. The use of agriculture residues as low-cost substrates for the production of industrial enzymes is a significant way to reduce production cost. ![]() Industrial production of enzymes on large scale is associated mainly with substrate. To use xylanase prominently in bleaching process it should be stable at high temperature and alkaline pH. The most practical approach is the screening for naturally occurring microbial strains capable of secreting cellulose-free xylanases under optimized fermentation conditions. To use xylanase for pulp treatment, it is preferable to use cellulose-free xylanases, since the cellulase may adversely affect the quality of the paper pulp. Xylanase secretion often associates with low or high amount of cellulases. Several species of Bacillus and filamentous fungi secrete high amounts of extracellular xylanases. Microorganisms are the rich sources of xylanases, produced by diverse genera and species of bacteria, actinomycetes, and fungi. Applications of xylanase avoid the use of chemicals that are expensive and cause pollution. Xylanases are of industrial importance, which can be used in paper manufacturing to bleach paper pulp, increasing the brightness of pulp and improving the digestibility of animal feed and for clarification of fruit juices. Xylanase (E.C 3.2.1.8) degrades β-1, 4 xylan by cleaving β-1, 4 glycosidic linkages randomly, and the products are xylose and xylo-oligosaccharides like xylobiose. In simplest forms, xylans are linear homopolymers that contain D-xylose monomers linked through β-1, 4–glycosyl bonds. It is likely that xylan molecules covalently link with lignin phenolic residues and also interact with polysaccharides, such as pectin and glucan. Xylan is found mainly in the secondary cell wall and is considered to be forming an interphase between lignin and other polysaccharides. In temperate softwoods, xylans are less abundant and may comprise about 8% of the total dry weight. Xylan is the most abundant noncellulosic polysaccharide present in both hardwoods and annual plants and accounts for 20–35% of the total dry weight in tropical plant biomass. In addition, the xylanase was also capable of producing high-quality xylo-oligosaccharides, which indicated its application potential not only in pulp biobleaching processes but also in the nutraceutical industry. For birchwood xylan, the enzyme gave a Km 5.26 mg/mL and Vmax 277.7 μmol/min/mg, respectively. The enzyme was active on birchwood xylan and little active on p-nitrophenyl xylopyranoside but not on Avicel, CMC, cellobiose, and starch, showing its absolute substrate specificity. The optimum temperature and pH for the enzyme activity were 50☌ and pH 8.0. The molecular weight of xylanase was ~29.8 kDa. The extracellular xylanase was isolated by ammonium sulfate (80%) precipitation and purified using ion exchange chromatography. A thermoalkalophilic new species of Bacillus, similar to Bacillus arseniciselenatis DSM 15340, produced extracellular xylanase under solid state fermentation when wheat bran is used as carbon source. ![]()
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