DHA (docosahexaenoic acid)-producing Schizochytrium limacinum gene engineering strain, and construction method and application thereof

The invention provides a DHA (docosahexaenoic acid)-producing Schizochytrium limacinum gene engineering strain, and a construction method and application thereof, belonging to the technical field of biochemical engineering. The DHA-producing Schizochytrium limacinum gene engineering strain is an engineering strain formed by integrating a malic enzyme gene expression cassette into Schizochytrium limacinum genome, wherein the malic enzyme gene expression cassette sequentially contains a promoter, a malic enzyme gene and a terminator. The construction method of the Schizochytrium limacinum gene engineering strain comprises the following steps: constructing a homologous recombinant segment containing the malic enzyme gene expression cassette; and transferring the homologous recombinant segment into Schizochytrium limacinum to perform homologous recombination, and screening to obtain the Schizochytrium limacinum gene engineering strain. The invention also provides a method for preparing DHA by using the Schizochytrium limacinum gene engineering strain, which comprises the following steps: culturing the Schizochytrium limacinum gene engineering strain by using a seed culture medium, and inoculating into a fermentation culture medium to prepare the DHA. The Schizochytrium limacinum gene engineering strain can produce DHA at high yield, and has the advantages of simple construction method, high efficiency and lower cost.