Browsing by Author "Thidarat Nimchua"

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    Alkaliphilic endoxylanase from lignocellulolytic microbial consortium metagenome for biobleaching of eucalyptus pulp
    (2012-12-01) Chawannapak Weerachavangkul; Thanaporn Laothanachareon; Katewadee Boonyapakron; Sarunyou Wongwilaiwalin; Thidarat Nimchua; Lily Eurwilaichitr; Kusol Pootanakit; Yasuo Igarashi; Verawat Champreda; Mahidol University; Thailand National Center for Genetic Engineering and Biotechnology; Graduate School of Agricultural and Life Sciences The University of Tokyo
    Enzymatic pre-bleaching by modification of pulp fibers with xylanases is an attractive approach to reduce the consumption of toxic bleaching chemicals in the paper industry. In this study, an alkaliphilic endoxylanase gene was isolated from metagenomic DNA of a structurally stable thermophilic lignocellulose-degrading microbial consortium using amplification with conserved glycosyl hydrolase family 10 primers and subsequent genome walking. The full-length xylanase showed 78% sequence identity to an endo-β-1,4-xylanase of Clostridium phytofermentans and was expressed in a ma ture form with an N-terminal His6 tag fusion in Escherichia coli. The recombinant xylanase Xyn3F was thermotolerant and alkaliphilic, working optimally at 65-70°C with an optimal pH at 9- 10 and retaining > 80% activity at pH 9, 60°C for 1 h. Xyn3F showed a V max of 2,327 IU/mg and K m of 3.5 mg/ml on birchwood xylan. Pre-bleaching of industrial eucalyptus pulp with no prior pH adjustment (pH 9) using Xyn3F at 50 IU/g dried pulp led to 4.5-5.1% increase in final pulp brightness and 90.4-102.4% increase in whiteness after a single-step hypochlorite bleaching over the untreated pulp, which allowed at least 20% decrease in hypochlorite consumption to achieve the same final bleaching indices. The alkaliphilic xylanase is promising for application in an environmentally friendly bleaching step of kraft and soda pulps with no requirement for pH adjustment, leading to improved economic feasibility of the process. © The Korean Society for Microbiology and Biotechnology.
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    The effect of mechano-enzymatic treatment on the characteristics of cellulose nanofiber obtained from kenaf (Hibiscus cannabinus L.) bark
    (2019-02-01) Koranat Narkpiban; Chularat Sakdaronnarong; Thidarat Nimchua; Phitsanu Pinmanee; Paweena Thongkred; Thitivara Poonsawat; Kasetsart University, Kamphaeng Saen Campus; Mahidol University; Thailand National Center for Genetic Engineering and Biotechnology
    © 2019 North Carolina State University. Cellulose nanofiber (CNF) was successfully isolated from kenaf bark by microfluidization at 20,000 psi for 40 passes. The combination of hydrothermal process and xylanase treatment prior to CNF isolation led to effective cellulose purification. The fiber used for enzymatic pretreatment for CNF isolation had an 85.9% whiteness index and 85.1% cellulose content. The crystallinity of the cellulose extracted from the kenaf bark continued to increase with successive treatments, as indicated by X-ray diffraction analysis. In addition, the enzyme-treated fiber showed increased thermal stability, as shown by thermogravimetric analysis. After CNF isolation, morphological characterization of the CNF was performed via field emission-scanning electron microscopy and transmission electron microscopy. The CNF had an average diameter that ranged from 5 to 10 nm and no undesired elemental contamination, as evidenced by energy dispersive X-ray spectroscopy. The mechano-enzymatic treatments used in this work to obtain CNF were judged to be a promising technique for the fabrication of biomedical and other high-value materials.