Augmentation of exopolysaccharide synthesis and its influence on biofunctional properties of polysaccharide in Sanghuangporus vaninii via targeted overexpression of phosphoglucomutase

Phosphoglucomutase (PGM) is considered an essential catalyst in polysaccharide biosynthesis, plays a pivotal role in the early stage of carbon metabolism and the synthesis of nucleotide sugars. Polysaccharides are important active components of Sanghuangporus vaninii. Based on the transcriptomic data, the successful cloning and re-annotation of the putative 1353 - bp PGM took place, which encodes a protein of 49.45 kDa. In order to elucidate the function of this gene, overexpression and interference transformation systems were constructed in S. vaninii. The results revealed that the PGM is primarily responsible for regulating the interconversion between glucose-1-phosphate and glucose-6-phosphate. An up - regulation of PGM expression resulted in a significant increase in extracellular polysaccharide content, quantified at 7.72 % and 15.15 %, whereas a down - regulation of PGM expression resulted in a significant increase in intracellular polysaccharide content (33.68 % and 38.24 %). The antioxidant capacity of intracellular polysaccharide in strain, including hydroxyl radical scavenging, superoxide anion radical scavenging, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, ABTS⁺ radical scavenging and FRAP scavenging was significantly increased by RNA interference with the expression of PGM, while the overexpression of PGM was found to enhance the antioxidant capacity of extracellular polysaccharide to a certain degrees. Furthermore, the modulation of PGM expression had a significant impact on polysaccharide metabolic pathways, resulting in alterations in monosaccharide composition and impacting the content of cell wall components, and the microstructure of polysaccharides. These findings elucidate the polysaccharide biosynthetic pathway in S. vaninii, highlighting the PGM as a prime target for the propagation of high-yield polysaccharide-producing strains. This study stands as a basic reference for amplifying polysaccharide production via strategic metabolic regulation.