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Study on Enzymatic Properties of Feeding Xylanase
Xylanase is a group of enzymes capable of breaking down xylan into oligosaccharides and xylose. It includes exo-β-1,4-xylanase, endo-β-1,4-xylanase, and β-xylosidase [1]. Xylanase has broad applications in various fields such as feed, food, paper, textiles, medicine, and energy. As a feed enzyme, it effectively reduces the anti-nutritional effects of xylan, improving the digestion and absorption of roughage by livestock and poultry. In pulp bleaching, xylanase helps reduce the use of chlorine, addressing environmental concerns in industrial processes. Additionally, xylanase breaks down hemicellulose in plants, producing pentose sugars that can be used for manufacturing xylitol, alcohol, and organic acids, playing a key role in the biotransformation of renewable resources [2].
In the early stages of laboratory research, a highly efficient xylan-degrading strain was isolated [3]. This experiment aimed to investigate the enzymatic properties of xylanase produced through solid-state fermentation, including optimal pH, pH stability, optimal temperature, thermal stability, and resistance to pepsin and trypsin. The goal was to gain a deeper understanding of the enzyme's characteristics and provide guidance for its practical application.
**1 Materials and Methods**
1.1 Xylanase was obtained through solid-state fermentation in our laboratory.
1.2 Reagents
Oat xylan (X0627), pepsin (P7000), and trypsin (T1005) were purchased from Sigma. The DNS reagent was prepared according to GB/T 23874-2009. All other reagents were of analytical grade.
1.3 Enzyme Activity Determination
Enzyme activity was measured using the DNS spectrophotometric method, as described in GB/T 23874-2009. One unit of enzyme activity is defined as the amount of enzyme required to release 1 μmol of reducing sugar per minute from a 5 mg/mL xylan solution at 37°C and pH 5.5.
**2 Experimental Design**
2.1 Optimum Reaction pH
Different pH buffers (0.1 mol/L, ranging from 2.0 to 8.0) were used, with sodium dihydrogen phosphate-citrate buffer for pH ≤ 8.0 and glycine-sodium hydroxide buffer for pH > 8.0. Enzyme activity was measured according to national standards. The highest activity was set as 100%, and other conditions were expressed as a percentage of this value.
2.2 pH Stability
Buffers with varying pH (2.0–9.0) were mixed in equal volumes and incubated at 37°C for 4 hours. After cooling, enzyme activity was determined using the standard method. The highest activity was considered 100%.
2.3 Optimum Reaction Temperature
The reaction was carried out at different temperatures (30–70°C) using a buffer at the optimal pH. Enzyme activity was measured to determine the optimal temperature.
2.4 Thermal Stability
The enzyme was treated at 50, 55, and 60°C for 10–120 minutes. Enzyme activity was measured to assess thermal stability, with untreated enzyme activity set as 100%.
2.5 Effect of Pepsin and Trypsin on Xylanase Activity
Xylanase was incubated with pepsin (pH 2.0, 0.01 mg/mL) and trypsin (pH 7.0, 0.2 mg/mL) at 37°C for 30, 60, and 90 minutes. Enzyme activity was measured to evaluate the impact of these proteases. The untreated sample was used as the control.