Chemical pretreatment-independent saccharifications of xylan and cellulose of rice straw by bacterial weak lignin-binding xylanolytic and cellulolytic enzymes

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Author list: Teeravivattanakit T., Baramee S., Phitsuwan P., Sornyotha S., Waeonukul R., Pason P., Tachaapaikoon C., Poomputsa K., Kosugi A., Sakka K., Ratanakhanokchai K.

Publisher: American Society for Microbiology

Publication year: 2017

Journal: Applied and Environmental Microbiology (0099-2240)

Volume number: 83

Issue number: 22

ISSN: 0099-2240

eISSN: 1098-5336

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032681222&doi=10.1128%2fAEM.01522-17&partnerID=40&md5=8125d9dcca51c40af68baff3038246ae

Languages: English-Great Britain (EN-GB)

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Abstract

Complete utilization of carbohydrate fractions is one of the prerequisites for obtaining economically favorable lignocellulosic biomass conversion. This study shows that xylan in untreated rice straw was saccharified to xylose in one step without chemical pretreatment, yielding 58.2% of the theoretically maximum value by Paenibacillus curdlanolyticus B-6 PcAxy43A, a weak lignin-binding trifunctional xylanolytic enzyme, endoxylanase/β-xylosidase/arabinoxylan arabinofuranohydrolase. Moreover, xylose yield from untreated rice straw was enhanced to 78.9% by adding endoxylanases PcXyn10C and PcXyn11A from the same bacterium, resulting in improvement of cellulose accessibility to cellulolytic enzyme. After autoclaving the xylanolytic enzyme-treated rice straw, it was subjected to subsequent saccharification by a combination of the Clostridium thermocellum endoglucanase CtCel9R and Thermoanaerobacter brockii β-glucosidase TbCglT, yielding 88.5% of the maximum glucose yield, which was higher than the glucose yield obtained from ammoniatreated rice straw saccharification (59.6%). Moreover, this work presents a new environment-friendly xylanolytic enzyme pretreatment for beneficial hydrolysis of xylan in various agricultural residues, such as rice straw and corn hull. It not only could improve cellulose saccharification but also produced xylose, leading to an improvement of the overall fermentable sugar yields without chemical pretreatment. © 2017 American Society for Microbiology.

Keywords

Cellulolytic enzyme, glucose, Xylanolytic enzyme, Xylose