Ye Shichao Xue Ting He Wenjin Ye Bingying Wei Fang Chen Youqiang
Xylanase is an important industrial enzyme preparation. A large number of different types and functions of xylanase have been isolated from various organisms and have been widely used in the paper, feed, food and wine industries. In this paper, the research status and progress of xylanase in terms of source, classification, structure and application are reviewed, and its application prospects are prospected.
Xylanase overview
Hemicellulose is a polymeric carbohydrate that is a mixture of several different types of polysaccharides that bind tightly to cellulose in plant cell walls, including xylan, glucomannan, arabinoxylan, xyloglucan, and galacto Various components such as grape mannan. Hemicellulose is the second most abundant polysaccharide in nature, and xylan is the main component in hemicellulose, which accounts for 15%-30% of dry weight in angiosperms; xylan in gymnosperms The content accounts for 7%-12%.
Xylan is a complex polysaccharide whose backbone is connected to β-D-xylopyranoside by a β-1,4-glycosidic bond; in the polymer backbone β-D-pyridyl 4-O-methyl-α-D-glucuronic acid, α-L-arabinose, etc. are attached to the O-2 or O-3 position of the xylose residue, wherein the softwood xylan structure is higher in the former. High; at the same time, its C2 or C3 is often acetylated, 70%-80% of the xylan of angiosperms such as hardwood is acetylated on C2 or C3, which affects the solubility of xylan in water. It means that a large part of xylan in nature is difficult to be decomposed. Xylanase is a multi-component complex enzyme system that degrades xylan into xylooligosaccharides and xylose, and has great potential for the utilization of semi-fibrous polysaccharide resources and industrial applications.
Source of xylanase
The structure of xylan is complicated, and there are often different types of branches in the main chain. Therefore, in order to degrade and utilize xylan, various enzymes are also required. Xylanase is a poly-complex enzyme in a broad sense, and is a general term for a class of enzymes that can degrade xylan. It is widely used in nature and is found in bacteria, fungi, snails, crustaceans, ruminants, marine algae, terrestrial plant tissues, and the like. The reported xylanase-producing microorganisms include Trichoderma, Aspergillus, Penicillium, Streptomyces, Bacteria, etc. Among them, xylanases produced by Trichoderma, Aspergillus, and bacteria are studied, and are derived from different sources. Xylanases, their enzymatic properties also vary.
Classification of xylanase
The xylanases in a broad sense mainly include three types: exo-β-1,4-xylanase (EC 3.2.1.92), which acts on the non-reducing ends of oligo-xylose and xylan; Endo-β-1,4-xylanase (EC 3.2.1.8), the most important enzyme for the degradation of xylan, acts on the internal chain of β-1,4-xylan to cut β-1. 4-glycosidic bond, which cleaves xylan and long-chain oligo-xylose from different sites and produces hydrolysates such as xylobiose and xylo-oligosaccharide; β-1,4-xylosidase (EC) 3.2.1.37), catalyzing the release of xylose residues by hydrolyzing the ends of xylooligosaccharides. The narrowly defined xylanase refers to the endo-β-1,4-xylanase.
Structure of xylanase
The xylanase has a wide range of sources and a complicated structure. If the amino acid sequence homology and hydrophobicity of the glycoside hydrolase catalytic region are analyzed, the glycoside hydrolase can be divided into a plurality of families. It has been found that the xylanase mainly contains G/11 and F/10 family hydrolases according to the hydrolase classification system. The F/10 family xylanase comprises an endo-β-1,4-xylanase, an endo-β-1,3-xylanase, etc., and has a relatively large molecular weight and a small pI value. It can act on p-nitrophenyl cellobiose and p-nitrobenzene. Xylo-oligosaccharide is the main product of substrate degradation; G/11 family xylanase is single, pI value is large, molecular weight is generally small, on wood The specificity of the glycan is relatively high, and the enzymatic hydrolyzed product is mainly xylose. Of course, some xylanase activities were also found in the glycoside hydrolase species 5, 7, 8, 16, 26, 43, 52, 62 families.
Xylanase, according to its genetic structure and function analysis, some xylanases only contain catalytic zone (CD), and some may contain some non-catalytic zones, such as cellulose binding zone, in addition to the catalytic zone. (CBD), xylan binding region (XBD), thermostable structural region, linking sequence and other non-catalytic regions of unknown function, and catalytic region.
Application of xylanase
Application of xylanase in feed
Anti-nutritional factors such as arabinoxylan are contained in the cell wall of the grain, which affects the absorption of nutrients by the poultry. Xylanase is used in animal feeds with glucanase, pectinase, cellulase, protease, amylase, phytase, etc. These enzymes can destroy the integrity of anti-nutritional factors such as arabinoxylan. Thereby reducing the viscosity of raw materials and promoting the digestion and absorption of feed nutrients by animals. Liao Xigu et al found that in the corn-bean meal-hybrid-based diet, 250g/t and 500g/t xylanase were added to the basal diet, respectively. Compared with the control group, it increased by 2.77% and 4.96%, and the feed-to-weight ratio decreased by 1.85% and 2.11%, respectively. It was concluded that the production performance of meat ducks was improved by using xylanase. Gong Min et al. studied the changes of physiological and biochemical indexes of piglets by adding arabinoxylanase to the diet, and concluded that adding arabinoxylanase to the diet can increase the daily weight gain of weaned piglets and affect the growth performance of piglets. Biochemical indicators of related blood.
Ye Shichao Xue Ting He Wenjin Ye Bingying Wei Fang Chen Youqiang
Xylanase is an important industrial enzyme preparation. A large number of different types and functions of xylanase have been isolated from various organisms and have been widely used in the paper, feed, food and wine industries. In this paper, the research status and progress of xylanase in terms of source, classification, structure and application are reviewed, and its application prospects are prospected.
Xylanase overview
Hemicellulose is a polymeric carbohydrate that is a mixture of several different types of polysaccharides that bind tightly to cellulose in plant cell walls, including xylan, glucomannan, arabinoxylan, xyloglucan, and galacto Various components such as grape mannan. Hemicellulose is the second most abundant polysaccharide in nature, and xylan is the main component in hemicellulose, which accounts for 15%-30% of dry weight in angiosperms; xylan in gymnosperms The content accounts for 7%-12%.
Xylan is a complex polysaccharide whose backbone is connected to β-D-xylopyranoside by a β-1,4-glycosidic bond; in the polymer backbone β-D-pyridyl 4-O-methyl-α-D-glucuronic acid, α-L-arabinose, etc. are attached to the O-2 or O-3 position of the xylose residue, wherein the softwood xylan structure is higher in the former. High; at the same time, its C2 or C3 is often acetylated, 70%-80% of the xylan of angiosperms such as hardwood is acetylated on C2 or C3, which affects the solubility of xylan in water. It means that a large part of xylan in nature is difficult to be decomposed. Xylanase is a multi-component complex enzyme system that degrades xylan into xylooligosaccharides and xylose, and has great potential for the utilization of semi-fibrous polysaccharide resources and industrial applications.
Source of xylanase
The structure of xylan is complicated, and there are often different types of branches in the main chain. Therefore, in order to degrade and utilize xylan, various enzymes are also required. Xylanase is a poly-complex enzyme in a broad sense, and is a general term for a class of enzymes that can degrade xylan. It is widely used in nature and is found in bacteria, fungi, snails, crustaceans, ruminants, marine algae, terrestrial plant tissues, and the like. The reported xylanase-producing microorganisms include Trichoderma, Aspergillus, Penicillium, Streptomyces, Bacteria, etc. Among them, xylanases produced by Trichoderma, Aspergillus, and bacteria are studied, and are derived from different sources. Xylanases, their enzymatic properties also vary.
Classification of xylanase
The xylanases in a broad sense mainly include three types: exo-β-1,4-xylanase (EC 3.2.1.92), which acts on the non-reducing ends of oligo-xylose and xylan; Endo-β-1,4-xylanase (EC 3.2.1.8), the most important enzyme for the degradation of xylan, acts on the internal chain of β-1,4-xylan to cut β-1. 4-glycosidic bond, which cleaves xylan and long-chain oligo-xylose from different sites and produces hydrolysates such as xylobiose and xylo-oligosaccharide; β-1,4-xylosidase (EC) 3.2.1.37), catalyzing the release of xylose residues by hydrolyzing the ends of xylooligosaccharides. The narrowly defined xylanase refers to the endo-β-1,4-xylanase.
Structure of xylanase
The xylanase has a wide range of sources and a complicated structure. If the amino acid sequence homology and hydrophobicity of the glycoside hydrolase catalytic region are analyzed, the glycoside hydrolase can be divided into a plurality of families. It has been found that the xylanase mainly contains G/11 and F/10 family hydrolases according to the hydrolase classification system. The F/10 family xylanase comprises an endo-β-1,4-xylanase, an endo-β-1,3-xylanase, etc., and has a relatively large molecular weight and a small pI value. It can act on p-nitrophenyl cellobiose and p-nitrobenzene. Xylo-oligosaccharide is the main product of substrate degradation; G/11 family xylanase is single, pI value is large, molecular weight is generally small, on wood The specificity of the glycan is relatively high, and the enzymatic hydrolyzed product is mainly xylose. Of course, some xylanase activities were also found in the glycoside hydrolase species 5, 7, 8, 16, 26, 43, 52, 62 families.
Xylanase, according to its genetic structure and function analysis, some xylanases only contain catalytic zone (CD), and some may contain some non-catalytic zones, such as cellulose binding zone, in addition to the catalytic zone. (CBD), xylan binding region (XBD), thermostable structural region, linking sequence and other non-catalytic regions of unknown function, and catalytic region.
Application of xylanase
Application of xylanase in feed
Anti-nutritional factors such as arabinoxylan are contained in the cell wall of the grain, which affects the absorption of nutrients by the poultry. Xylanase is used in animal feeds with glucanase, pectinase, cellulase, protease, amylase, phytase, etc. These enzymes can destroy the integrity of anti-nutritional factors such as arabinoxylan. Thereby reducing the viscosity of raw materials and promoting the digestion and absorption of feed nutrients by animals. Liao Xigu et al found that in the corn-bean meal-hybrid-based diet, 250g/t and 500g/t xylanase were added to the basal diet, respectively. Compared with the control group, it increased by 2.77% and 4.96%, and the feed-to-weight ratio decreased by 1.85% and 2.11%, respectively. It was concluded that the production performance of meat ducks was improved by using xylanase. Gong Min et al. studied the changes of physiological and biochemical indexes of piglets by adding arabinoxylanase to the diet, and concluded that adding arabinoxylanase to the diet can increase the daily weight gain of weaned piglets and affect the growth performance of piglets. Biochemical indicators of related blood.
Application of xylanase in food industry
Xylanase has been widely used in bread processing, xylanase can act on the water-insoluble xylan trunk, release water-soluble arabinoxylan, reduce the molecular weight of water-insoluble xylan, and improve The quality of the bread baking. The distribution of water in the gluten and starch caused by extensive hydrolysis of arabinoxylan makes the dough softer and more viscous. The xylan in wheat affects the rheological properties of the dough and the quality of the noodle, while the xylanase can effectively alter the rheological properties of the dough. In the study of the effect of xylanase on the processing of biscuits, UYSAL H found that xylanase can increase the tensile strength and softness of the dough, thereby reducing the hardness and increasing the stretch of the biscuit. The xylose monomer, a xylanase degradation product, can be derived from xylitol, which acts as a sweetener for diabetic or obese patients and is a popular sugar substitute on the market.
Application of xylanase in wine industry
Xylanase can act on xylan in plant cell wall, promote hemicellulose degradation and starch release, improve fermentation efficiency, and increase ethanol yield. At the same time, it can reduce the viscosity in fermentation broth and improve beer. Clearness improves the taste of beer.
Other applications
Xylanase has a wide range of functions. In addition to the above effects, xylanase can also be used in biological experiments. In the preparation of vegetable oil, starch and soluble coffee, the effect of xylanase can be reduced. The viscosity of the liquid increases the concentration efficiency; the xylose, a degradation product of xylanase, can be used as a fermentation substrate for some microorganisms, and is further used for fermentation to produce valuable fuels and chemical raw materials.
Outlook
Xylanase has a wide range of functions in the industry, and a large amount of xylan is contained in the raw materials for producing feed and used in papermaking. The presence of anti-nutritional factors such as xylan is not conducive to the absorption and utilization of nutrients in the feed by animals; xylan can hinder the dissolution of lignin in the pulp. For the whiter and brighter pulp, the amount of chloride used in the bleaching process cannot be used. Control; the outer layer of the fruit and vegetable is a hard cell wall, and the soluble xylan, pectin and other viscous substances will make the viscosity of the extract too large, which will make the subsequent concentration and drying work difficult. The degradation of xylan by xylanase can be a good way to solve the above problems.
Xylanase can degrade xylan into xylooligosaccharides, improve the efficiency of industrial production, and reduce production costs. Therefore, many researchers have screened strains producing xylanase from extreme environments such as soil, acid and alkali. At present, most xylanases are derived from the fermentation production of various original strains. The advantage of the xylanase produced by the original strain is that it produces a complex enzyme, which has a more thorough effect on xylan. Of course, more and more studies have been carried out using genetic engineering methods to obtain xylanase. The xylanase gene has been expressed in E. coli, Saccharomyces cerevisiae, Pichia pastoris and other hosts, although this engineering strain expresses it. The xylanase is relatively simple, but its significance cannot be ignored. For some xylanases from extreme environmental microorganisms, it is difficult to artificially culture and produce enzymes under daily conditions. If the target gene can be obtained and heterologously expressed, it will have great value in production.
Different strains produce different enzymes. At present, there have been many reports on high-yield xylanase strains or strains producing xylanases, and some have been successfully made into enzyme preparations in the industry. High-quality xylanase brings low cost and high efficiency to the papermaking, feed, food and other industries. We believe that modern biotechnology methods such as protein engineering and genetic engineering will be applied to xylanase research, which will promote the research speed of xylanase and bring extensive and significant results to paper, food, beverage and health care products. Economic and social benefits.
Coarse grain usually refers to rice, wheat, corn, soybean and potato five crops other than the grain and bean crops. The main are: sorghum, millet, buckwheat (sweet buckwheat, buckwheat), oats (naked oats), barley, millet, barley millet, barley millet, grain amaranth and beans (kidney beans), mung beans, adzuki beans (adzuki beans, adzuki beans), broad beans, peas, cowpea, lentils (soldier beans), black beans and so on. It is characterized by short growing period, small planting area, special planting area, low yield, and generally contain rich nutrients. The ancient Chinese medicine book "Huangdi Neijing" records that "five grains are for raising, five fruits are for helping, five livestock are for benefiting, and five vegetables are for filling". Some trace elements, such as iron, magnesium, zinc and selenium, are more abundant in coarse grains than in refined grains. The value of these trace elements to human health is considerable. Coarse grains are also richer in potassium, calcium, vitamin E, folic acid and bioflavonoids than refined grains.
Whole Grains are rich in nutrients. Oats, for example, are rich in protein; Millet is rich in tryptophan and carotene. Beans are high in quality protein; Sorghum is rich in fatty acids and iron; Tubers contain carotene and vitamin C. In addition, coarse grain still has the effect of reducing weight. Such as corn also contains a lot of magnesium, magnesium can strengthen intestinal wall peristalsis, promote the excretion of body waste, is very beneficial to weight loss.
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