Breeding and genomic analysis of the high PQQ-producing strain Hyphomicrobium denitrificans NJTU3-43

Pyrroloquinoline quinone (PQQ) exhibits significant physiological functions including antioxidant activity, anti-aging effects and immune enhancement, demonstrating promising applications in medicine, cosmetic and health care fields. Recently, the biological production of PQQ has attracted considerable attentions owing to the green and environmentally friendly properties. This study successfully isolated the PQQ-producing bacterium Hyphomicrobium denitrificans NJTU3 and optimized fermentation parameters. A high PQQ-producing mutant strain NJTU3-43 was bred through random mutagenesis. Genomic analysis revealed multiple copies of PQQ-related genes, highlighting its advantages in PQQ production and methanol metabolism. Comparative genomic analysis identified electron transfer flavoprotein (ETF) mutations as the key factor in enhancing PQQ synthesis efficiency of strain NJTU3-43. Finally, PQQ production was improved to 208.4 mg/L with a PQQ content of 57.9 mg/g by strain NJTU3-43 using methanol as the substrate in fed-batch fermentation. This represents the highest PQQ content reported to date. Overall, this study excavated a superior strain with high efficiency in PQQ production, laying the foundation for its large-scale production.