Recombinant Pichia pastoris for producing small-molecular hyaluronic acids and construction method thereof

The invention discloses a recombinant Pichia pastoris for producing small-molecular hyaluronic acids and a construction method thereof, belonging to the technical field of bioengineering. Hyaluronic acid synthase hasA derived from Streptococcus zooepidemicus and UDP-glucose dehydrogenase tuaD derived from Bacillus subtilis are expressed in recombinant Pichia pastoris GS115 host to implement production of hyaluronic acids. Meanwhile, hyaluronidase derived from hirudo is integrated to the Pichia pastoris genome and subjected to secretion expression by constitutive promoters with different intensities; the secretion expression level of the hyaluronidase is controlled to prepare small-molecular hyaluronic acid products with different molecular weights; and the prepared products have different ranges of molecular weight, and have instruction and reference meanings for directly producing small-molecular hyaluronic acids within a specified range from microbes. The recombinant Pichia pastoris lays certain foundation for high-efficiency preparation of small-molecular hyaluronic acids, and is suitable for industrial production.