A novel hybrid organosolv: Steam explosion method for the efficient fractionation and pretreatment of birch biomass
Artikel i vetenskaplig tidskrift, 2018

Background: The main role of pretreatment is to reduce the natural biomass recalcitrance and thus enhance saccharification yield. A further prerequisite for efficient utilization of all biomass components is their efficient fractionation into well-defined process streams. Currently available pretreatment methods only partially fulfill these criteria. Steam explosion, for example, excels as a pretreatment method but has limited potential for fractionation, whereas organosolv is excellent for delignification but offers poor biomass deconstruction. Results: In this article, a hybrid method combining the cooking and fractionation of conventional organosolv pretreatment with the implementation of an explosive discharge of the cooking mixture at the end of pretreatment was developed. The effects of various pretreatment parameters (ethanol content, duration, and addition of sulfuric acid) were evaluated. Pretreatment of birch at 200 °C with 60% v/v ethanol and 1% w/wbiomassH2SO4was proven to be the most efficient pretreatment condition yielding pretreated solids with 77.9% w/w cellulose, 8.9% w/w hemicellulose, and 7.0 w/w lignin content. Under these conditions, high delignification of 86.2% was demonstrated. The recovered lignin was of high purity, with cellulose and hemicellulose contents not exceeding 0.31 and 3.25% w/w, respectively, and ash to be < 0.17% w/w in all cases, making it suitable for various applications. The pretreated solids presented high saccharification yields, reaching 68% at low enzyme load (6 FPU/g) and complete saccharification at high enzyme load (22.5 FPU/g). Finally, simultaneous saccharification and fermentation (SSF) at 20% w/w solids yielded an ethanol titer of 80 g/L after 192 h, corresponding to 90% of the theoretical maximum. Conclusions: The novel hybrid method developed in this study allowed for the efficient fractionation of birch biomass and production of pretreated solids with high cellulose and low lignin contents. Moreover, the explosive discharge at the end of pretreatment had a positive effect on enzymatic saccharification, resulting in high hydrolyzability of the pretreated solids and elevated ethanol titers in the following high-gravity SSF. To the best of our knowledge, the ethanol concentration obtained with this method is the highest so far for birch biomass.

Delignification

Inhibitor-free biomass

Cellulose-enriched biomass

Hybrid organosolv-steam explosion

Cellic CTec2

Birch

Ethanol

High-gravity

Fractionation

Författare

Leonidas Matsakas

Luleå tekniska universitet

Christos Nitsos

Luleå tekniska universitet

Vijayendran Raghavendran

University of Sheffield

Chalmers, Biologi och bioteknik, Industriell bioteknik

Olga Yakimenko

Luleå tekniska universitet

Gustav Persson

Chalmers, Fysik, Eva Olsson Group

Eva Olsson

Chalmers, Fysik, Eva Olsson Group

Ulrika Rova

Luleå tekniska universitet

Lisbeth Olsson

Chalmers, Biologi och bioteknik, Industriell bioteknik

P. Christakopoulos

Luleå tekniska universitet

Biotechnology for Biofuels

1754-6834 (eISSN)

Vol. 11 1 160

Ämneskategorier

Förnyelsebar bioenergi

Kemiska processer

Bioenergi

DOI

10.1186/s13068-018-1163-3

PubMed

29930706