There are 2 types of malic acid fermentation: one-step fermentation and two-step fermentation. The microbes used in different fermentation procedures are likewise different.
( 1) The stress of the one-step fermentation technique consist of Aspergillus flavus, Aspergillus oryzae, as well as Aspergillus parasiticus, all of which utilize different sugars including glucose as substrates to produce L-malic acid.
( 2) The two-step fermentation technique uses Rhizopus sinensis or Rhizopus aureus to biosynthesize fumaric acid from glucose, and after that transforms fumaric acid to L – Malic acid.
The one-step fermentation method primarily utilizes Aspergillus flavus, which can produce L-malic acid from numerous sweet raw materials such as glucose, maltose, sucrose, fructose and starch. However, the tool is made complex, and also various other natural acids such as fumaric acid are usually created during the fermentation procedure, which brings problems to splitting up as well as purification, and it is tough to obtain high-purity crystals. Furthermore, the acid manufacturing is reduced, as well as the conversion price to sugar is low (30%～ 40%) %), the cycle is long (at least additionally require 5 days), so developed production has not been realized in your home and also abroad thus far.
In the primary step of the two-step fermentation technique, rhizopus is utilized to ferment sugars to produce fumaric acid, that is, fumaric acid fermentation. Glucose is used as the sugar here, and sugar can be obtained from starch via double-enzyme hydrolysis. The second action is to place yeast or germs right into the fumaric acid produced over for fermentation, as well as transform fumaric acid into L-malic acid, that is, conversion fermentation. Utilizing this method, the optimum conversion rate of malic acid to sugar can reach more than 60%, yet nevertheless, the fermentation cycle is too long, and also it takes 8-9 days to build up. Although the two-step method is the same as the one-step technique, scholars at home and abroad are constantly exploring and also have made some valuable development, but there is still no report on industrial production.
Whether it is one-step or two-step fermentation, if starch is utilized as raw material, it requires to be hydrolyzed before usage to make it right into glucose, and the best hydrolysis technique for starch is double-enzyme hydrolysis. Currently, the industrial manufacturing approaches of L-malic acid in the house as well as abroad are all immobilized cell improvement approaches. The method is to first of all cultivate a lot of germs with high fumarase activity, collect the microorganisms as well as fix them with ideal providers such as carrageenan, after that placed them into a column activator, use salt fumarate as a substratum, and flow with The activator, militarized by the fumarase in the debilitated cells, can easily transform fumaric acid into L-malic acid with almost no spin-offs, as well as the conversion price is as high as 95%. Compared to the above two techniques, this method is straightforward, economical and effective, so it has come to be the very first method for commercial production.