Process for preparing sialic acid by adopting fermentation method and application of sialic acid

The invention discloses a process for preparing sialic acid by adopting a fermentation method and application of the sialic acid. The process comprises the following steps: (1) adding aluminum hydroxide powder into a fermentation liquor filtrate containing polysialic acid, adding ethanol under a stirring condition, uniformly stirring, then standing for a period of time, and carrying out solid-liquid separation after a crystallization precipitate is precipitated, so as to obtain a polysialic acid solid; and (2) adding the polysialic acid solid into a hydrochloric acid solution, hydrolyzing under a heating condition, and neutralizing the obtained hydrolysate to obtain a neutralized solution containing sialic acid. And (3) adding a decolorizing agent into the neutralized solution for decolorizing treatment, then adding ethanol into the obtained decolorized solution, uniformly stirring, then standing for a period of time, carrying out solid-liquid separation after a crystal precipitate is precipitated, and then w