Application of the most popular pullulan polysacch

2022-07-29
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Application of pullulan polysaccharide in the preservation of agricultural products (Part I)

Abstract: the production strains of pullulan, the influencing factors of fermentation process, the properties of pullulan and its application in the preservation of agricultural products in recent years were introduced

preface

pullulan is also translated into pullulan, pullulan, pullulan or Pullulan in Chinese. It is an extracellular polysaccharide produced by Aureobasidium blastosporum α- 1,6-glycosidic bond combines with maltose to form homopolysaccharide, that is, glucose α- 1,4-glycosidic bond to form maltotriose, and then α- The 1,6-glycosidic bond is combined with another maltotriose and thus repeatedly connected to form a high molecular polysaccharide. α- 1, 4-glycosidic bond the same as α- The ratio of 1,6-glycosidic bond is 2:1, and the degree of polymerization (D.P) is 100-5000. Molecular weight: 4.8x104-2.2x106 (the average molecular weight of commodity pullulan is 2x105, which is composed of about 480 maltotriose)

the research of pullulan polysaccharide began in West Germany, and the British have also done a lot of work in theory. Japan has conducted systematic research, especially on production process and product application, and has obtained a large number of patents. Pullulan polysaccharide can be produced by direct fermentation of starch hydrolysate, sucrose or other sugars. It is easy to dissolve in water, with low viscosity, no gel, no aging, can be processed and shaped at will, and has no toxic side effects. It is a promising industrial polysaccharide. There have been many reports about pullulan to make the measurement range larger. This paper will introduce the producing strains of pullulan, the influencing factors of fermentation process, the properties of pullulan and its application in the preservation of agricultural products

1. Pullulan producing strain

pullulan is an extracellular polysaccharide secreted by Aureobacidium pullulans. It is an extracellular polysaccharide produced by the growth and metabolism of Aureobasidium pullulans in the culture medium. Part of the sugar in the culture medium is used as a nutrient source for growth and reproduction, and most of it is produced by the complex enzyme system in the cell. After the sugar is exhausted, pullulan polysaccharide is decomposed to maintain cell development. Because pullulan is widely used, Chinese researchers have also developed pullulan producing strains in recent years. Tanjialin et al. Conducted fermentation conditions and medium-sized scale-up experiments on the mutant n28 of as3.2765. Gu Caisi and Du Lisheng also isolated pullulans from Pinus massoniana Needles and seawater in Guilin, Guangxi, respectively. Nashumin isolated a strain A22 producing achromatic extracellular polysaccharides from the cocoon of the Canadian bee cutting insect. According to the hermanides nijhof classification system, it will be more and more valued by the society like aureobasidum pullulans R. zhaozhiwei and others isolated a wild-type aureobasidum pullulans FT1 from the leaves of pomegranate growing in the West Kunming mountain. A strain with stable properties was obtained from FT1 through protoplast regeneration, Mutant strain R45 with certain industrial value. We will always adhere to our main idea

in addition to the above, there are many kinds of Aureobasidium pullulans that can produce pullulans. Their morphological characteristics and physiological changes are quite different, and their ability to produce pullulans is also different. Strains with excellent performance of broad-spectrum pullulans usually have yeast type and mycelial type morphological characteristics, with more and uniform budding spores and less or no melanin in the fermentation broth, After fermentation, the process is simple

2. Factors affecting the fermentation process and yield determination of pullulan polysaccharide

at present, pullulan polysaccharide products of different specifications have been produced, but they have not been put into production on a large scale. Most strains are still in the stage of laboratory research. Different fermentation conditions of Aureobasidium pullulans were different. However, it was found that the selection of carbon source, nitrogen source, metal ion, starting ion and phosphate all affected the fermentation of pullulan. As a carbon source, edible starch has higher sugar production efficiency than industrial starch, soluble starch and glucose. All kinds of ammonium salts such as (NH4) 2SO4, NH4Cl and (NH4) 2CO3 can be used as nitrogen sources to make Aureobasidium brevis grow, but the amount of ammonium salts has an effect on the sugar conversion. The optimal concentration of NH4 + is 0.02%. K + and po43- can promote the production of pullulan polysaccharide, and the optimal concentration range of K + is 0.02%-0.04%, more than 0.04% will inhibit the production of pullulan polysaccharide. The optimal initial pH of fermentation was about 6. Generally, the optimal culture temperature for pullulan production is about 28 ℃

generally, the fermentation broth is centrifuged at 2500r/min for 10min, the supernatant is added with 95% ethanol of the same volume as "made in China 2025" to precipitate pullulan polysaccharide, and the precipitated polysaccharide is dried at 80 ℃ for 5h and weighed

(to be continued)

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