Bioprospecting xylanase enzymes from environmental samples

Abstract

Hemicelluloses are a group of heteropolysaccharides which accounts for 33% by dry weight of the total lignocellulosic biomass. Xylan is one of the most important and abundantly found hemicellulose which has diverse structures according to the source from which it is extracted. Due to its structural diversity, xylan is hydrolysed by a class of xylanase enzymes into its monomeric xylose subunits. These xylose residues when treated with yeasts get converted into ethanol which can be used as a supplement along with natural fuels. Ethanol production by biological means not only reduces the cost of production but also decreases the formation of inhibitors which are formed during chemical pretreatment of xylan that hampers the process of fermentation. Besides bioethanol production xylanases have also got many other productive uses in various industries such as paper pulp bleaching, oil extraction, food additives, bakeries, detergents, fodder industries, etc. Twelve strains were isolated from environmental samples like cow dung, leaf litter, waste water, soil, termites, etc. The isolated strains were confirmed for xylanase production on xylan agar plates and Congo red assay. Activity of endoxylanases (1-4 â-D xylanases) was determined by measuring the amount of reducing sugar from xylan which was estimated spectrophotometrically with 3,5 dinitrosalycilic acid using xylose as standard. The isolated strains produced maximum xylanase at 37ᵒC at a pH of 6.8 to 7.0 after 120 h of incubation. Xylanases extracted from different strains showed maximum activity at an optimal pH of 7.0 and optimal temperature 40ᵒC. The value of km and Vmax recorded for highest xylanase producing strain JS4(7) was recorded to be 0.25mg/ml and 83µg/ml/min. The morphology of the two highest xylanase producing strains JS3(4) and JS4(7) was found to be bacillus and coccus respectively under SEM imaging.