Provided are a microorganism for producing a pantoic acid, and a construction method therefor and an application thereof. The microorganism for producing the pantoic acid is obtained by knocking out a gene in Escherichia coli and introducing an exogenous gene. The obtained microorganism is Escherichia coli that is registered in the China General Microbiological Culture Collection Center with an accession number of CGMCC No. 21699. A pantoic acid synthesis pathway has been opened up, and accumulation of the pantoic acid can be achieved in a fermentation process.

Disclosed are means and methods for the fermentative production of an oligosaccharide of interest by a genetically engineered microbial cell, wherein concomitant biosynthesis of pantothenic acid is reduced or abolished.

The present invention provides a genetically engineered pantoic acid-producing strain having or having an enhanced NADH-dependent acetohydroxy acid reductoisomerase, a method for producing the strain, a method for producing D-pantoic acid using the strain, and use thereof in production of D-pantoic acid.