Abstract
Xylanase is an important enzyme with potential application in the degradation of xylan component in the lignocellulosic biomass. There are very few reports on the production of cellulase free xylanases especially by yeast strains which have great potential in paper and pulp industry in removing the hemicellulose from the treated or untreated pulp. In this study, P. hubeiensis NCIM 3574 isolated in our laboratory produced significant levels of extracellular cellulase free xylanase (2480 IU/g DSS) in solid state fermentation (SSF) using wheat bran and xylan. It also produced high levels of β-xylosidase (198 IU/g DSS) when grown in SSF using ground nut oil cake and xylan. These highest activities were obtained when fermented Koji was extracted with 1% NaCl supplemented with 0.5% of Triton X-100. These are the highest activities reported so far from yeast strains in the available literature. The crude xylanase preparation of P. hubeiensis produced xylooligosaccharides (XOS) without xylose proving its potential for XOS production with no further requirement of downstream processing. The XOS as prebiotic show beneficial effect on gut microflora such as Lactobacilli and Bifidobacteria which suppress the activity of pathogenic organisms. This xylanase also has a potential application as a bio-bleaching agent in paper and pulp industry.
Highlights
The results showed that it produced high activities of xylanase and β-xylosidase in both submerged fermentation (SmF) and solid state fermentation (SSF)
Very high xylanase (565 IU/ml) and β-xylosidase (5.4 IU/ml) activities were secreted in the medium on 3rd and 5th day respectively in SmF when P. hubeiensis was grown in fermentation medium containing 2% xylan (Figure 1)
P. hubeiensis NCIM 3574 isolated from decaying sandal wood produced a cellulase free xylanase and β-xylosidase
Summary
Cellulose and hemicellulose can be converted to a number of bulk chemicals. Cellulases and xylanases degrade lignocellulosic biomass in to simple sugars that can be converted to value-added chemicals including biofuels. The high cost of lignocellulose degrading enzymes poses the problems in their application for biofuel production. Aspergillus strains are the potent producers of both β-glucosidase [1] and β-xylosidase [2] [3]. Most of the commercial enzyme preparations are deficient in both β-glucosidases and β-xylosidases [4]. It is necessary to supplement the commercial biomass degrading enzymes with such enzyme preparations containing high amounts of β-glucosidases and β-xylosidases to achieve complete biomass hydrolysis
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