Steam Explosion Pretreatment of Beechwood. Part 1: Comparison of the Enzymatic Hydrolysis of Washed Solids and Whole Pretreatment Slurry at Different Solid Loadings

Abstract

Steam explosion is a well-known process to pretreat lignocellulosic biomass in order to enhance sugar yields in enzymatic hydrolysis, but pretreatment conditions have to be optimized individually for each material. In this study, we investigated how the results of a pretreatment optimization procedure are influenced by the chosen reaction conditions in the enzymatic hydrolysis. Beechwood was pretreated by steam explosion and the resulting biomass was subjected to enzymatic hydrolysis at glucan loadings of 1% and 5% employing either washed solids or the whole pretreatment slurry. For enzymatic hydrolysis in both reaction modes at a glucan loading of 1%, the glucose yields markedly increased with increasing severity and with increasing pretreatment temperature at identical severities and maximal values were reached at a pretreatment temperature of 230 °C. However, the optimal severity was 5.0 for washed solids enzymatic hydrolysis, but only 4.75 for whole slurry enzymatic hydrolysis. When the glucan loading was increased to 5%, glucose yields hardly increased for pretreatment temperatures between 210 and 230 °C at a given severity, and a pretreatment temperature of 220 °C was sufficient under these conditions. Consequently, it is important to precisely choose the desired conditions of the enzymatic hydrolysis reaction, when aiming to optimize the pretreatment conditions for a certain biomass.

Assessment of the effectiveness of liquid hot water and steam explosion pretreatments of fast-growing poplar (Populus trichocarpa) wood

“…1. Based on the results, it can be observed, that the applied pretreatments caused a large increase in the efficiency of enzymatic hydrolysis, and these findings are consistent with studies of other researchers (Li et al 2014;Pielhop et al 2016;Michelin and Teixeira 2016;Imman et al 2018;Balan et al 2020). The average glucose yield after enzymatic hydrolysis was 46.0 mg/g native biomass, whereas the average xylose yield was 23.1 mg/g native biomass.…”

“…Additionally, the energy consumption during this process is relatively moderate (lower than in the LHW pretreatment), there is a possibility of using large biomass particles as a feedstock and the process was even developed on an industrial scale. Many studies have been carried out on this subject for different kinds of lignocellulosic material, which proves that the process is well known and documented (Brownell et al 1986;Brownell and Saddler 1987;Nunes and Pourquie 1996;Ballesteros et al 2006;Fang et al 2011;Martín-Sampedro et al 2011;Liu et al 2013;Li et al 2015;Pielhop et al 2016;Simangunsong et al 2018;Balan et al 2020). Biomass during the steam explosion process is treated with high-pressure steam typically at a temperature of 160-260 °C.…”

Steam Explosion Pretreatment of Beechwood. Part 2: Quantification of Cellulase Inhibitors and Their Effect on Avicel Hydrolysis

“…All steam explosion pretreatment experiments were performed with a custom-built steam gun system (Industrieanlagen Planungsgesellschaft m.b.H., Graz, Austria), as described in the companion publication [24]. Briefly, we performed a series of pretreatment experiments with severities (log R 0 ) ranging from 3.0 to 5.25 at reaction temperatures between 160 and 230 • C using 250 g of air-dried beechwood per run ( Table 1) (1) Table 1.…”

“…For example, Djioleu et al characterized 24 different prehydrolyzates of dilute acid pretreated switchgrass, but, to the best of our knowledge, no such comprehensive dataset exists for autohydrolysis pretreatments. Thus, we analyzed in this work the prehydrolyzates derived from a series of experiments aiming at the optimization of steam explosion pretreatment of beechwood [24] for their content of inhibitors and quantified their inhibitory effect on the enzymatic hydrolysis of Avicel as a model of a microcrystalline cellulosic substrate.…”

Evaluation of the Hydrolysis Efficiency of Bacterial Cellulose Gel Film after the Liquid Hot Water and Steam Explosion Pretreatments

“…In similar studies by Kashcheyev et al [ 41 ], the hydrolysis efficiency of the crude and untreated bacterial cellulose was 56.3–66.6%, thus similar to the values obtained in this study for raw cellulose. It should also be stated that the hydrolysis efficiency of the non-purified pretreated bacterial cellulose significantly exceeded the hydrolysis efficiency of the plant biomass [ 35 , 44 , 45 ]. In studies conducted by Antczak et al [ 28 ], the glucose yield from the enzymatic hydrolysis of cellulose isolated from P. trichocarpa wood subjected to the LHW and SE pretreatment methods was up to 67%.…”