Aureobasidium pullulans strain capable of producing poly-beta-L-malic acid by utilizing starch and application thereof

Abstract

The invention discloses an Aureobasidium pullulans strain capable of producing poly-beta-L-malic acid by utilizing starch and application thereof. The Aureobasidium pullulans strain is classified andnamed Aureobasidium pullulans GXL-1 under the preservation number of CCTCC NO: M 2018519 at China Center for Type Culture Collection (address: Wuhan University, Wuhan, China) since August 1, 2018. TheAureobasidium pullulans GXL-1 disclosed by the invention can directly use raw starch or a liquefied starch solution as a carbon source to produce poly-beta-L-malic acid at a mass concentration of 57g / L by carrying out batch fermentation at 30 DEG C without addition of a fermentation accelerator and growth factors; and moreover, no melanin is produced during the fermentation process. The Aureobasidium pullulans GXL-1 has the advantages of being low in fermentation cost, easy to realize product purification, and simple in process; and thus, the Aureobasidium pullulans GXL-1 has very great production potentials.

Description

technical field [0001] The invention belongs to the technical field of microbial application, in particular to Aureobasidium pullulans for producing polymalic acid from starch and its application. Background technique [0002] Polymalic acid [poly(β-L-malic acid), PMA] is a new type of polymer compound made of L-malic acid as the only monomer through the dehydration polyester of α-hydroxyl and β-carboxyl groups. Water solubility, biodegradability, biocompatibility and chemical modification have broad application prospects in medicine, food, agriculture and environmental governance. The production methods of polymalic acid include chemical synthesis and biosynthesis. The chemical synthesis of polymalic acid has complicated steps, more by-products, smaller molecular weight and higher cost; however, the biological synthesis of polymalic acid is simple in operation, less by-products, larger in molecular weight and lower in cost. Synthesis of polymalic acid is a current researc...

AI Technical Summary

Problems solved by technology

[0004] It can be seen that many researchers have obtained many strains of Aureobasidium pullulans capable of synthesizing polymalic acid through natural breeding or mutation breeding, but through comparison, it is found that these strains still have some shortcomings in the process of fermenting and producing polymalic acid: (1) High-concentration glucose is used as a carbon source. On the one hand, the cost of raw materials is high, and on the other hand, high-concentration glucose has a substrate inhibitory effect on the growth of bacteria, which limits the increase in the production of polymalic acid; when molasses is used as a carbon source, due to Molasses itself has a darker color and more impurities. Although the cost of raw materials has decreased, it will increase the cost of extraction and purification of polymalic acid and treatment of fermentation waste liquid

(2) Although the yield of polymalic acid is as high as 62.27g / L, sodium fumarate needs to be added as a fermentation accelerator in the medium, which increases the cost of fermentation raw materials

(3) A certain amount of corn steep liquor or corn extract must be added to the fermentation medium of the above three types of Aureobasidium pullulans. On the one hand, the cost of fermentation raw materials is increased. On the other hand, due to the complex composition of corn steep liquor or corn extract, the quality is difficult to control , there is uncertainty about the effect on the fermentation process

(4) The fermentation temperature of the above three types of Aureobasidium pullulans is 25°C, and microbial fermentation is an exothermic process, so a large amount of cooling water is required to maintain the lower fermentation temperature, thereby increasing the operating cost of fermentation equipment

Although Aureobasidium pullulans ( Aureobasidium pullulans ) GXZ-6 can use tapioca starch, corn starch, wheat starch, soluble starch, starch saccharification solution, and maltose syrup as carbon sources to ferment polymalic acid, and it can be produced in batches at 30 °C More than 60g / L polymalic acid can be obtained by fermentation, but it produces melanin during the fermentation process, which usually makes the downstream separation and extraction of metabolites difficult, affecting the yield of polymalic acid product and product appearance

Images