Metabolomics profiling reveals the mechanism of increased pneumocandin B0 production by comparing mutant and parent strains

Effect of fatty acids on intracellular pneumocandin B0 storage in the fermentation of Glarea lozoyensis

The natural product pneumocandin B0 is the precursor of the antifungal drug caspofungin. To explore the relationship between pneumocandin B0 and oil. We found that the addition of 1 g/L of oil to the fermentation medium is more conducive to the production of pneumocandin B0. The metabolic reaction mechanism was explored using different fatty acids and the results showed that stearic acid and acetic acid increased the total production of pneumocandin B0 by 22.98% and 9.08%, respectively, as well as increasing the content of intracellular lipid droplets. We also analyzed gene expression and pathway differences between the two different fatty acids using transcriptome analyses. The addition of both acetic acid and stearic acid promoted an active pentose phosphate pathway, providing cells with higher intracellular reducing power. We found that the addition of fatty acids can lead to lipid accumulation, and lipid droplets can sequester lipophilic secondary metabolites such as pneumocandin B0 to reduce cell damage. These results provide novel insights into the relationship between pneumocandin B0 biosynthesis and fatty acids in G. lozoyensis. In addition, this study provides important genetic information for improving the yield of pneumocandin B0 through a strategy of metabolic engineering in the future.

Glyap1 regulates pneumocandin B0 synthesis by controlling the intracellular redox balance in Glarea lozoyensis

Pneumocandin B₀, the precursor of the antifungal drug caspofungin, is a lipohexapeptide produced by the fungus Glarea lozoyensis. Oxidative stress and the resulting production of reactive oxygen species (ROS) are known to be involved in the regulation of pneumocandin B₀ biosynthesis. In this study, the Glyap1 gene of Glarea lozoyensis, a homologue of the yeast redox regulator YAP1, was knocked out. The intracellular ROS levels of the resulting ΔGlyap1 strain were higher than in the wild-type strain, which was caused by the downregulated expression of superoxide dismutase (SOD) and catalase (CAT). Compared with the wild-type strain, ΔGlyap1 exhibited an oxidative phenotype throughout its life cycle, which resulted in significantly higher pneumocandin B₀ production per unit biomass. In addition, ΔGlyap1 showed growth inhibition and decreased pneumocandin B₀ production in the presence of CCl₄, which leads to strong oxidative stress. To overcome the strain's sensitivity, a three-stage antioxidant addition strategy was developed. This approach significantly improved the growth of ΔGlyap1 while maintaining a high pneumocandin B₀ production per unit biomass, which reached 38.78 mg/g DCW. Notably, this result represents a 50% increase over the wild-type strain. These findings provide new insights into the regulatory mechanisms that control pneumocandin B₀ production under oxidative stress, which may be applied to improve the production of other secondary metabolites. KEY POINTS: • Glyap1 is involved in expression of redox and pneumocandin B₀ synthesis-related genes. • Addition of a three-stage antioxidant alleviated the sensitivity of ΔGlyap1 strain. • The yield of pneumocandin B₀ per unit biomass of ΔGlyap1 strain was 38.78 mg/g DCW.

Omics Approaches Applied to Penicillium chrysogenum and Penicillin Production: Revealing the Secrets of Improved Productivity

Penicillin biosynthesis by Penicillium chrysogenum is one of the best-characterized biological processes from the genetic, molecular, biochemical, and subcellular points of view. Several omics studies have been carried out in this filamentous fungus during the last decade, which have contributed to gathering a deep knowledge about the molecular mechanisms underlying improved productivity in industrial strains. The information provided by these studies is extremely useful for enhancing the production of penicillin or other bioactive secondary metabolites by means of Biotechnology or Synthetic Biology.

Comparative Transcriptomics Analysis of the Responses of the Filamentous Fungus Glarea lozoyensis to Different Carbon Sources

The natural product pneumocandin B₀ is the precursor of the antifungal drug caspofungin. We found that replacing glucose in the initial fermentation medium with 20 g/L fructose is more conducive to pneumocandin B₀ production and biomass accumulation. In order to explore the mechanism of the different metabolic responses to fructose and glucose, we used each as the sole carbon source, and the results showed that fructose increased the total pneumocandin B₀ yield and biomass by 54.76 and 13.71%, respectively. Furthermore, we analyzed the differences of gene expression and metabolic pathways between the two different carbon sources by transcriptomic analysis. When fructose was used as the carbon source, genes related to the pentose phosphate pathway (PPP), glycolysis and branched-chain amino acid metabolism were significantly upregulated, resulting in increased intracellular pools of NADPH and acetyl-CoA in Glarea lozoyensis for cell growth and pneumocandin B₀ product synthesis. Interestingly, the pneumocandin B₀ biosynthetic gene cluster and the genes of the TCA cycle were significantly downregulated, while the FAS genes were significantly upregulated, indicating that more acetyl-CoA was used for fatty acid synthesis. In particular, we found that excessive synthesis of fatty acids caused lipid accumulation, and lipid droplets can sequester lipophilic secondary metabolites such as pneumocandin B₀ to reduce cell damage, which may also be an important reason for the observed increase of pneumocandin B₀ yield. These results provide new insights into the relationship between pneumocandin B₀ biosynthesis and carbon sources in G. lozoyensis. At the same time, this study provides important genomic information for improving pneumocandin B₀ production through metabolic engineering strategies in the future.

Mutagenesis of echinocandin B overproducing Aspergillus nidulans capable of using starch as main carbon source

Echinocandin B, a kind of antimycotic with cyclic lipo-hexapeptides, was produced by fermentation with Aspergillus nidulans using fructose as main carbon source. The objective of this study was to screen a high-yield mutant capable of using cheap starch as main carbon source by atmospheric and room temperature plasma (ARTP) treatment in order to decrease the production cost of echinocandin B. A stable mutant A. nidulans ZJB19033, which can use starch as optimal carbon source instead of expensive fructose, was selected from two thousands isolates after several cycles of ARTP mutagenesis. To further increase the production of echinocandin B, the optimization of fermentation medium was performed by response surface methodology (RSM), employing Plackett-Burman design (PBD) followed by Box-Behnken design (BBD). The optimized fermentation medium provided the optimal yield of echinocandin B, 2425.9 ± 43.8 mg/L, 1.3-fold compared to unoptimized medium. The results indicated that the mutant could achieve high echinocandin B production using cheap starch as main carbon source, and the cost of carbon sources in fermentation medium reduced dramatically by about 45%.

Enhancement of Pneumocandin B0 Production in Glarea lozoyensis by Low-Temperature Adaptive Laboratory Evolution

The production of pneumocandin B0 is limited by feedback inhibition. Here, low-temperature adaptive laboratory evolution (ALE) was used to improve the production capacity of Glarea lozoyensis by enhancing its membrane permeability. After 50 cycles of ALE, the pneumocandin B0 production of the endpoint strain (ALE50) reached 2131 g/L, which was 32% higher than the starting strain (ALE0). ALE50 showed a changed fatty acid composition of the cell membrane, which-+h increased its permeability by 14%, which in turn increased the secretion ratio threefold. Furthermore, ALE50 showed increased intracellular proline and acetyl-CoA concentrations, superoxide dismutase (SOD), and catalase (CAT) activity, as well as total antioxidant capacity. The slight biomass decrease in ALE50 was accompanied by decreased isocitrate dehydrogenase (ICDH) and glucose-6-phosphate dehydrogenase (G6PDH) activity. Finally, a putative model of the accumulation and secretion of pneumocandin B0 in ALE50 was established. ALE is a promising method to release intracellular feedback inhibition.

Novel osmotic stress control strategy for improved pneumocandin B0 production in Glarea lozoyensis combined with a mechanistic analysis at the transcriptome level

Pneumocandin B₀, the precursor of the antifungal drug caspofungin, is a secondary metabolite of the fungus Glarea lozoyensis. In this study, we investigated the effects of mannitol as the sole carbon source on pneumocandin B₀ production by G. lozoyensis. The osmotic pressure is more important in enhancing pneumocandin B₀ production than is the substrate concentration. Based on the kinetic analysis, an osmotic stress control fed-batch strategy was developed. This strategy led to a maximum pneumocandin B₀ concentration of 2711 mg/L with a productivity of 9.05 mg/L/h, representing 34.67 and 6.47% improvements, respectively, over the best result achieved by the one-stage fermentation. Furthermore, G. lozoyensis accumulated glutamate and proline as compatible solutes to resist osmotic stress, and these amino acids also provided the precursors for the enhanced pneumocandin B₀ production. Osmotic stress also activated ROS (reactive oxygen species)-dependent signal transduction by upregulating the levels of related genes and increasing intracellular ROS levels by 20%. We also provided a possible mechanism for pneumocandin B₀ accumulation based on signal transduction. These findings will improve our understanding of the regulatory mechanisms of pneumocandin B₀ biosynthesis and may be applied to improve secondary metabolite production.

Biosynthesis of pneumocandin lipopeptides and perspectives for its production and related echinocandins

Fungal diseases are a global public health problem. Invasive fungal infections pose a serious threat to patients with compromised immune systems, such as those undergoing organ or bone marrow transplants, cancer, or HIV/AIDS. Pneumocandins are antifungal lipohexapeptides of the echinocandin family that noncompetitively inhibit of 1,3-β-glucan synthase of fungal cell wall and provide the precursor for the semisynthesis of caspofungin, which is widely used as first-line therapy for invasive fungal infections. Recently, the biosynthetic steps leading to formation of pneumocandin B₀ and echinocandin B have been elucidated, and thus, provide a framework and attractive model for further design new antifungal therapeutics around natural variations in echinocandin structural diversities via genetic and chemical tools. In this article, we analyze the biosynthetic pathway of pneumocandins and other echinocandins, provide an update on the array of pneumocandin analogues generated by genetic manipulation, and summarize advances in the enhancement of pneumocandin B₀ production by random mutagenesis and fermentation optimization. We also give offer advice on the development of improved pneumocandin drug candidates and more efficient production of pneumocandin B₀.