Abstract
The present study reports the production of high-level cellulase-free xylanase from Penicillium citrinum isolate HZN13. The variability in xylanase titers was assessed under both solid-state (SSF) and submerged (SmF) fermentation. SSF was initially optimized with different agro-waste residues, among them sweet sorghum bagasse was found to be the best substrate that favored maximum xylanase production (9643 U/g). Plackett–Burman and response surface methodology employing central composite design were used to optimize the process parameters for the production of xylanase under SSF. A second-order quadratic model and response surface method revealed the optimum conditions for xylanase production (sweet sorghum bagasse 25 g/50 ml; ammonium sulphate 0.36 %; yeast extract 0.6 %; pH 4; temperature 40 °C) yielding 30,144 U/g. Analysis of variance (ANOVA) showed a high correlation coefficient (R 2 = 97.63 %). Glutaraldehyde-activated calcium-alginate-immobilized purified xylanase showed recycling stability (87 %) up to seven cycles. Immobilized purified xylanase showed enhanced thermo-stability in comparison to immobilized crude xylanase. Immobilization kinetics of crude and purified xylanase revealed an increase in K m (12.5 and 11.11 mg/ml) and V max (12,500 and 10,000 U/mg), respectively. Immobilized (crude) enzymatic hydrolysis of sweet sorghum bagasse released 8.1 g/g (48 h) of reducing sugars. Xylose and other oligosaccharides produced during hydrolysis were detected by High-Performance Liquid Chromatography. The biomass was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray and Fourier Transformation Infrared Spectroscopy. However, this is one of the few reports on high-level cellulase-free xylanase from P. citrinum isolate using sweet sorghum bagasse.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0484-9) contains supplementary material, which is available to authorized users.
Highlights
Xylan is the major structural polysaccharide constituent of hard and soft wood and is the second most abundant renewable resource
The present study reports the production of highlevel cellulase-free xylanase from Penicillium citrinum isolate HZN13
response surface methodologies (RSM) has been used to optimize the production of microbial xylanases, less work has been reported on xylanase production by SSF using P. citrinum isolate
Summary
Xylan is the major structural polysaccharide constituent of hard and soft wood and is the second most abundant renewable resource. Crude enzyme preparations are cost effective as they bypass the high cost involved in downstream processing Such preparations have been employed as cocktails for enzymatic hydrolysis of biomass which requires a pool of hemicellulolytic enzymes. RSM has been used to optimize the production of microbial xylanases, less work has been reported on xylanase production by SSF using P. citrinum isolate. We report the characterization of a fungal isolate for the production of high-level cellulase-free xylanase from a variety of agro-waste residues. The isolated P. citrinum isolate HZN13 was used for xylanase production through a sequentially designed PBD and RSM statistical process optimization using sweet sorghum bagasse. Reports on high-level xylanase from P. citrinum isolate induced by sweet sorghum bagasse are scare
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