The invention relates to a preparation method of small molecular weight
dendrobium candidum polysaccharides. The preparation method comprises following steps: A,
bacterial strain activation and expanding culture are carried out, wherein under aseptic conditions, an appropriate amount of a
liquid culture medium is used for preparing a
fusarium avenaceum bacterium suspension; B,
high pressure homogenization is repeated for 5 to 10 times using a
high pressure micro jet
homogenizer so as to obtain a
dendrobium candidum wall-broken homogenate; C,
fermentation culturing is carried out, wherein an appropriate amount of a
liquid culture medium is injected into a
fermentation tank, the
dendrobium candidum wall-broken homogenate and the
fusarium avenaceum bacterium suspension are weighed, and are delivered into the
fermentation tank for fermentation so as to obtain a fermentation liquid; and D,
polysaccharide purification is carried out, wherein after fermentation,
active carbon is used for decolouring, an obtained product is allowed to stand for 1h for absorption, filtering is carried out so as to remove residue and obtain a filtrate,
vacuum pumping filtration is carried out so as to obtain a precipitate, the precipitate is washed with
ethanol for three times, and
vacuum drying is carried out so as to obtain the small molecular weight
dendrobium candidum polysaccharides. The average molecular weight of the small molecular weight
dendrobium candidum polysaccharides is lower than 300kDa; and the small molecular weight
dendrobium candidum polysaccharides are capable of promoting propagation of
skin probiotics, increasing the density of langerhans cells on
skin, and improving
skin immunity.