High-Yielding Lovastatin Producer Aspergillus terreus Shows Increased Resistance to Inhibitors of Polyamine Biosynthesis

Abstract

The biosynthesis of pharmaceutically significant secondary metabolites in filamentous fungi is a multistep process that depends on a wide range of various factors, one of which is the intracellular content of polyamines. We have previously shown that in Aspergillus terreus lovastatin high-yielding strain (HY) exogenous introduction of polyamines during fermentation can lead to an increase in the production of lovastatin by 20–45%. However, the molecular mechanisms of this phenomenon have not been elucidated. In this regard, we carried out an inhibitory analysis at the key stage of polyamine biosynthesis, the conversion of L-ornithine to putrescine by the enzyme ornithine decarboxylase (ODC). A. terreus HY strain showed upregulation of genes for biosynthesis of polyamines, 3–10-fold, and increased resistance compared to the original wild-type strain upon inhibition of ODC on synthetic medium with 5 mM α-difluoromethylornithine (DFMO), by 20–25%, and 5 mM 1-aminooxy-3-aminopropane (APA), by 40–45%. The data obtained indicate changes in the metabolism of polyamines in A. terreus HY strain. The observed phenomenon may have a universal character among fungal producers of secondary metabolites improved by classical methods, since previously the increased resistance to ODC inhibitors was also shown for Acremonium chrysogenum, a high-yielding producer of cephalosporin C.

Polyamines Upregulate Cephalosporin C Production and Expression of β-Lactam Biosynthetic Genes in High-Yielding Acremonium chrysogenum Strain

“…Thus, OD 600 = 0.5 were ~2.7 × 10 7 CFU/mL for the A. chrysogenum WT strain and 1.6 × 10 6 CFU/mL for the A. chrysogenum HY strain. Industrial strains with overproduction of SMs, obtained using classical strain improvement (CSI) programs, often contain unwanted side mutations and "bottlenecks" that negatively affect the fitness of the strain, resistance, productivity, and adaptation to harsh fermentation conditions [2,50,51]. It is possible that the introduction of exogenous PAs could complement or correct some of these negative effects.…”

Exploitation of Sugarcane Bagasse and Environmentally Sustainable Production, Purification, Characterization, and Application of Lovastatin by Aspergillus terreus AUMC 15760 under Solid-State Conditions

“…Numerous fungi can generate various types of secondary metabolites, including enzymes, lipids, fats, and substances of great medical and industrial potential, such as lovastatin, a superior substrate for the hyper-production of the cholesterol lowering pharmaceutical drug [ 34 , 35 ]. One of these fungi is A. terreus, which is widely recognized for producing the compound lovastatin by submerged fermentation (SmF) or solid-state fermentation (SSF), both of which make use of lignocellulosic biomass and different synthetic media [ 9 , 17 , 36 , 37 , 38 , 39 ].…”

Fungal BGCs for Production of Secondary Metabolites: Main Types, Central Roles in Strain Improvement, and Regulation According to the Piano Principle

“…Therefore, strains improved in this way usually have lower viability than WT strains. This can be expressed as a slowdown in the growth rate, a decrease in the size of the colonies on agar media, a decrease in biomass during submerged cultivation, an increase in stress resistance, and many other complications [ 223 , 254 , 255 ]. As a result, after several tens of rounds of mutagenesis, a stage begins whereby, after the next mutagenic effect, it is no longer possible to obtain more active clones.…”