title: Purification, characterization and thermostability improvement of xylanase from Bacillus amyloliquefaciens and its application in pre-bleaching of kraft pulp.
abstract: Xylanases have important industrial applications but are most extensively utilized in the pulp and paper industry as a pre-bleaching agent. We characterized a xylanase from Bacillus amyloliquefaciens strain SK-3 and studied it for kraft pulp bleaching. The purified enzyme had a molecular weight of ~50 kDa with optimal activity at pH 9.0 and 50 °C. The enzyme showed good activity retention (85%) after 2 h incubation at 50 °C and pH 9.0. This enzyme obeyed Michaelis-Menten kinetics with regard to beechwood xylan with Kmand Vmaxvalues of 5.6 mg/ml, 433 μM/min/mg proteins, respectively. The enzyme activity was stimulated by Mn2+, Ca2+and Fe2+metal ions. Further, it also showed good tolerance to phenolics (2 mM) in the presence of syringic acid (no loss), cinnamic acid (97%), benzoic acid (94%) and phenol (97%) activity retention. The thermostability of xylanase was increased by 6.5-fold in presence of sorbitol (0.75 M). Further, pulp treated with 20U/g of xylanase (20IU/g) alone and with sorbitol (0.75M) reduced kappa number by 18.3 and 23.8%, respectively after 3 h reaction. In summary, presence of xylanase shows good pulp-bleaching activity, good tolerance to phenolics, lignin and metal ions and is amenable to thermostability improvement by addition of polyols. The SEM image showed significant changes on the surface of xylanase-treated pulp fiber as a result of xylan hydrolysis.
authors.affiliation: Environmental Microbiology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.|Amity Institute of Biotechnology, Amity University, Lucknow Campus, Malhaur, Near Railway Station, Gomti Nagar Extension, Lucknow, Uttar Pradesh, 226028, India.
authors.forename: Sharad
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Environmental Microbiology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India.
authors.forename: Izharul
authors.initials: I
authors.lastname: Haq
authors.affiliation: Amity Institute of Biotechnology, Amity University, Lucknow Campus, Malhaur, Near Railway Station, Gomti Nagar Extension, Lucknow, Uttar Pradesh, 226028, India.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Prakash
authors.affiliation: Microbiology Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Sudheer Kumar
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Environment Management Division, Central Pulp and Paper Research Institute, Post Box 174, Paper Mill Road, Himmat Nagar, Saharanpur, Uttar Pradesh, 247001, India.
authors.forename: Shivaker
authors.initials: S
authors.lastname: Mishra
authors.affiliation: Environmental Microbiology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan 31, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, 226001, India. araj@iitr.res.in.
authors.forename: Abhay
authors.initials: A
authors.lastname: Raj
keywords: Bacillus amyloliquefaciens; Kappa number; Purification; SEM; Thermostability; Xylanase