Ensiling of wheat straw decreases the required temperature in hydrothermal pretreatment

Abstract

BackgroundEnsiling is a well-known method for preserving green biomasses through anaerobic production of organic acids by lactic acid bacteria. In this study, wheat straw is subjected to ensiling in combination with hydrothermal treatment as a combined pretreatment method, taking advantage of the produced organic acids.ResultsEnsiling for 4 weeks was accomplished in a vacuum bag system after addition of an inoculum of Lactobacillus buchneri and 7% w/w xylose to wheat straw biomass at 35% final dry matter. Both glucan and xylan were preserved, and the DM loss after ensiling was less than 0.5%. When comparing hydrothermally treated wheat straw (170, 180 and 190°C) with hydrothermally treated ensiled wheat straw (same temperatures), several positive effects of ensiling were revealed. Glucan was up-concentrated in the solid fraction and the solubilisation of hemicellulose was significantly increased.Subsequent enzymatic hydrolysis of the solid fractions showed that ensiling significantly improved the effect of pretreatment, especially at the lower temperatures of 170 and 180°C.The overall glucose yields after pretreatments of ensiled wheat straw were higher than for non-ensiled wheat straw hydrothermally treated at 190°C, namely 74-81% of the theoretical maximum glucose in the raw material, which was ~1.8 times better than the corresponding yields for the non-ensiled straw pretreated at 170 or 180°C. The highest overall conversion of combined glucose and xylose was achieved for ensiled wheat straw hydrothermally treated at 180°C, with overall glucose yield of 78% and overall conversion yield of xylose of 87%.ConclusionsEnsiling of wheat straw is shown to be an effective pre-step to hydrothermal treatment, and can give rise to a welcomed decrease of process temperature in hydrothermal treatments, thereby potentially having a positive effect on large scale pretreatment costs.

The multi‐feedstock biorefinery – Assessing the compatibility of alternative feedstocks in a 2G wheat straw biorefinery process

“…Many research articles and industrial reports have addressed hydrothermal pretreatment as an effective pretreatment strategy for wheat straw biomass (Larsen, Petersen, Thirup, Li, & Iversen, 2008;Mosier et al, 2005;Petersen, Larsen, & Thomsen, 2009;Thomsen, Thygesen, & Thomsen, 2008). The reported optimized conditions differ slightly between different studies, due to differences in pretreatment unit and scale, but several authors have reported 190°C for 10 min as an optimum for wheat straw (Ambye-Jensen, Thomsen, Kádár, & Meyer, 2013;Ertas, Han, Jameel, & Chang, 2014;Zhang et al, 2014). Using existing pretreatment technology and infrastructure optimized for wheat straw biomass, it could be economically efficient to add biomass feedstock diversity to the biorefinery on a local/ regional supply basis.…”

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

“…These organosolv lignins were dry powders with a volume-based particle size of D [4,3] Wheat straw lignin (WSL) was a hydrothermally pretreated wheat straw sample that had been exhaustively enzymatically treated with a Cellic CTec2 enzyme cocktail from Novozymes (Bagsvaerd, Denmark). The wheat straw had first been hydrothermally pre-treated in a pilot plant facility (10 min, 190 °C) according to [22]. After pre-treatment, the insoluble fiber fraction was suspended to 4.5 wt% dry matter (DM) and treated for 48 h with a Cellic CTec2 at pH 5.1, 50 °C.…”

Cathode Assessment for Maximizing Current Generation in Microbial Fuel Cells Utilizing Bioethanol Effluent as Substrate

“…Bioethanol effluent was obtained through hydrothermal treatment of 1 kg wheat straw (Triticum aestivum L.) at 190˝C for 10 min on the Mini IBUS pretreatment pilot plant at Department of Chemical and Biochemical Engineering, Technical University of Denmark [24]. The pretreated slurry was separated by filtration into a filter cake and a filtrate.…”