Biological pretreatment of rice straw with cellulase-free xylanolytic enzyme-producing Bacillus firmus K-1: Structural modification and biomass digestibility

Journal article

Authors/Editors

Strategic Research Themes

2nd gen biofuels (Biofuels & Bio-refinery )

Publication Details

Author list: Baramee S., Siriatcharanon A.-K., Ketbot P., Teeravivattanakit T., Waeonukul R., Pason P., Tachaapaikoon C., Ratanakhanokchai K., Phitsuwan P.

Publisher: Elsevier

Publication year: 2020

Journal: Renewable Energy (0960-1481)

Volume number: 160

Start page: 555

End page: 563

Number of pages: 9

ISSN: 0960-1481

eISSN: 1879-0682

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088221088&doi=10.1016%2fj.renene.2020.06.061&partnerID=40&md5=182b5d51be4561c73e5eca7aa61c4052

Languages: English-Great Britain (EN-GB)

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Abstract

Biological pretreatment using microorganisms or enzymes offers an eco-friendly process for biomass processing. Herein, the efficiency of pretreatment of rice straw with the cellulase-free xylanolytic enzyme-producing Bacillus firmus K-1 and its enzymes was assessed. After pretreatment with strain K-1 (BRS), the xylan content in rice straw reduced significantly (21% removal), thus increasing exposure of the cellulose crystal structure (Crystallinity index (CrI) = 40.2%) and creating biomass porosity. Subsequent treatment of BRS with the in-house xylanase preparation (BRS-E) slightly increased xylan removal (30% removal). The reduction of xylan thus led to larger pore size and increased crystallinity (CrI = 42.8%). Compared to untreated rice straw (24% glucan conversion), hydrolysis of BRS and BRS-E with the commercial cellulase preparation Accellerase 1500 at 100 g/L substrate load showed comparable glucose yield, giving about 74% glucan conversion. The results indicate that the removal of xylan can enhance accessibility of cellulose to cellulases, although the lignin content was not reduced (24% for BRS and 25% for BRS-E). This work demonstrates a new insight into the improvement of pretreatment efficiency using a xylan-degrading microorganism, which is an alternative to conventional lignin removal by fungal pretreatment. © 2020 Elsevier Ltd

Keywords

Xylanolytic bacterium