Journal of biotechnology最新文献

Endophytic yeast strains are promising sources of various valuable bioactive compounds. However, studies on endophytic strains derived from lichen samples remains limited. In this study, we isolated and characterized Rhodotorula sp. Y090 from Usnea longissima and investigated its biosynthetic potential. Genome mining revealed distinct genetic features that differed from its closest relative strain R. graminis WP1. Ergothioneine (EGT) is a potent antioxidant and rare sulfur-containing histidine derivative. However, so far, the EGT biosynthetic enzymes by natural yeast strains have been limitedly studied. In this study, combining genome mining and transcriptomic analysis, genes encoding the potential enzymes for the production of EGT and xylose utilization were identified in Rhodotorula sp. Y090. Further studies demonstrated that Rhodotorula sp. Y090 was capable of producing EGT using xylose, glucose, glycerol, and sucrose as the sole carbon sources, and the highest titer reached 363.6mg/L in shake flask culture, which is significantly higher than that of the most reported levels in the other natural yeasts. Rhodotorula sp. Y090 also exhibited a good ability of EGT export, which could facilitate cost-effective production. These findings suggest that the lichen-derived endophytic yeast Rhodotorula sp. Y090 represents a promising natural candidate for bio-production of the potent antioxidant.

Nicotinamide mononucleotide (NMN) serves as a crucial precursor in the biosynthesis of NAD⁺ and has garnered significant attention in the food, dietary supplement, and cosmetic industries. This study engineered an Escherichia coli strain capable of high NMN production. Firstly, the strain with reduced NMN degradation and the ability to transport NMN extracellularly was constructed. Meanwhile, the gene encoding nicotinamide phosphoribosyltransferase (pncA) was disrupted to minimize substrate nicotinamide (NAM) degradation. Then, the induction starting point was optimized to alleviate the metabolic burden on the engineered strain. Subsequently, systematic remodeling of E. coli's glucose metabolism was conducted to enhance its suitability for NMN production by overexpressing key enzymes of the pentose phosphate pathway (Zwf and Gnd), knocking out genes related to the Entner-Doudoroff pathway (gntR and edd), and further attenuating the glycolytic pathway. Then, we concentrated on optimizing the cellular metabolic state, meticulously balancing intracellular redox homeostasis. Finally, using glucose and 2g/L of NAM as substrates, the extracellular NMN yield reached 4.96g/L, which is the highest yield reported so far in similar research. These findings contribute to the commercial production of NMN and offer valuable insights for constructing efficient cell factories for other nucleotide compounds.

Hyaluronic acid (HA) is a versatile biomolecule with applications in medicine, cosmetics, and pharmaceuticals. While traditionally extracted from animal tissues, HA is now predominantly produced through microbial fermentation. Microbial fermentation using strains such as Streptococcus zooepidemicus, Corynebacterium glutamicum, and Bacillus subtilis offers a more scalable and sustainable alternative to chemical and animal extraction methods. Recent studies reveal promising yields from engineered strains of Corynebacterium glutamicum and Bacillus subtilis, utilizing advanced metabolic and genetic techniques. Recent advancements in genetic and metabolic engineering, as well as synthetic biology, have addressed some challenges related to molecular weight, viscosity, and by-product formation. This review focuses on the microbial production of HA using engineered strains, encompassing producer organisms, metabolic engineering strategies, industrial-scale production, and key factors influencing molecular weight. Furthermore, it addresses the challenges and potential solutions associated with HA production. Additional research is necessary to develop more efficient and robust engineered strains that exhibit resistance to contamination and can utilize low-cost substrates, such as Pseudomonas putida and Halomonas spp. By overcoming these challenges, researchers can advance the industrial production of HA and expand its applications, thereby contributing to the growth of the HA market.