Optimization of selective acidolysis pretreatment for the valorization of wheat straw by a combined chemical and enzymatic process

Abstract

BACKGROUND: Advances in industrial biotechnology offer potential opportunities for economic utilization of abundantly available agricultural crop waste such as wheat straw, which is of great interest for advancement in xylo-oligosaccharides (XOS) and fermentable monosaccharides. In the present study, crude XOS and fermentable monosaccharides were sequentially produced by a combined chemical and enzymatic process from wheat straw.RESULTS: Maximum yield of XOS was 38.2% and the corresponding yield of glucose was 82.7% despite the wax barrier on the surface of wheat straw, while the acetic acid concentration was decreased from 20% to 5%. Pilot scale run produces 91.6 g XOS, 92.5 g xylose and 316.0 g glucose from 1000 g of wheat straw that means the utilization of 78.9% of xylan and 89.7% glucan constitutes.CONCLUSION: By removal of 65% xylan from wheat straw, enzymatic hydrolysis of cellulose was also improved efficiently although its polymer structure was almost kept inert during acetic acid pretreatment. ABBREVIATIONSAA acetic acid DC degraded chemicals HMF hydroxymethyl furfural SSTs stainless steel tubes XOS xylo-oligosaccharides Analytical method The sugars and degraded chemicals were detected by high-performance liquid chromatography (HPLC, Agilent 1260, J Chem Technol Biotechnol 2020; 95: 694-701Figure 3. (a) Enzymatic hydrolysis at various cellulase loading; (b) main sugar contents variations in 15 FPIU/g enzymatic hydrolysis; (c) changes of polysaccharide components in wheat straw before and after enzymatic hydrolysis and pretreatment. J Chem Technol Biotechnol 2020; 95: 694-701

Aliphatic Extractive Effects on Acetic Acid Catalysis of Typical Agricultural Residues to Xylo-Oligosaccharide and Enzymatic Hydrolysability of Cellulose

“…The reaction conditions were determined based on the difficulty in processing the poplar material and was based on previous literature. The reaction was carried out at 170°C for 20 min with an acetic acid concentration of 5% (v/v) [13,18,22]. After the reaction was terminated, the stainlesssteel reaction tube was immersed in cold water and cooled rapidly, followed by the phase separation of the acetic acid mixture of lignocelluloses.…”

“…Zhang et al obtained the highest XOS yield of 45.91% by pretreating CC with acetic acid, while achieving a cellulose conversion rate of more than 91%, thus achieving the efficient conversion of hemicellulose and cellulose [11]. Interestingly, the pretreatment of wheat straw (WS) with acetic acid resulted in the XOS yield of 38.21% [18]. This discrepancy in yield might be attributed to a variety of reasons, including the low xylan content, high lignin content, and recalcitrant structure of wood capillary.…”

Comparison of various organic acids for xylo-oligosaccharide productions in terms of pKa values and combined severity

“…Most widely studied pretreatment methods include physical, chemical, and biological methods. After pretreatment, hemicellulose can be converted into a mixture of oligosaccharides called xylo-oligosaccharides (XOS), an extremely valuable degradation product [ 5 ]. XOS are functional oligomers of sugars with straight as well as branched chains formed by 2–10 xylose molecules through β-1,4-glycosidic bonds [ 6 ].…”

Comparison of various orgainc acids for xylo-oligosaccharide productions in term of pKa values and combined severity

“…Most widely studied pretreatment methods include physical, chemical, and biological methods. After pretreatment, hemicellulose can be converted into a mixture of oligosaccharides called xylooligosaccharides (XOS), an extremely valuable degradation product [5]. XOS are functional oligomers of sugars with straight as well as branched chains formed by 2-10…”