Abstract
A novel treatment involving enzymatic hydrolysis using an acidic xylanase coupled with ultrasound was performed to improve the xylo-oligosaccharides (XOS) yield from corncob bran. The acidic xylanase (XynB) was purified to a most suitable pH, temperature, and operational parameters for ultrasound-assisted hydrolysis were determined. A preliminary mechanistic investigation was performed through circular dichroism (CD) spectroscopy, scanning electron microscope (SEM) and a laser particle size analyzer, and the effects of ultrasound on enzyme (XynB) and substrate (corncob bran) were assessed. The results show that the maximum XOS yield was 20.71% when the reaction pH and temperature were 4.3 and 50°C, the ultrasonic parameters were 50 kHz and 0.40 W/cm2, which was 2.55 fold higher than that obtained using a non-ultrasound-assisted enzymatic preparation. Mechanism studies indicated that ultrasonic pretreatment could reduce the β-fold content and increase the random coil content. Changes in structure and size of substrate were observed. The specific surface area of the XAC molecules is easy to carry out enzymatic reaction, which is beneficial to the production of XOS.
Highlights
Lignocellulosic materials are the most abundant organic residues worldwide
The optimal process conditions can be got from single factor experiment carried out by using four main factors: corncob concentration, pH, temperature and time: corncob was pretreated with 10% NaOH, with a liquid to solid ratios (L: S) of 10:1, at 100°C for 2 h
Maximum xylanase activity of 1807.9U/mL was observed in the presence of 6% corncob and 1.5% ammonium sulfate as the most appropriate inorganic nitrogen source
Summary
Lignocellulosic materials are the most abundant organic residues worldwide. Rice straw, corn cobs and tobacco straw are rich in lignocellulose and are potential industrial feeds (Chapla et al, 2012). Plant biomass is an economical, available, and renewable source of biofuel, bioenergy, and a variety of value-added biomolecules (Kumar and Satyanarayana, 2015). Corncob contains about 35% xylan, which is an essential by-product of that industry. It has many functions and can be used as animal feed or return to harvested farmland (Aachary and Prapulla, 2009). It is noteworthy that the xylan, a complex five-carbon polysaccharide, is the main component in hemicellulose (Liu et al, 2021).
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