Neurosporaxanthin Overproduction by Fusarium fujikuroi and Evaluation of Its Antioxidant Properties

Abstract

Neurosporaxanthin (NX) is a carboxylic carotenoid produced by some filamentous fungi, including species of the genera Neurospora and Fusarium. NX biosynthetic genes and their regulation have been thoroughly investigated in Fusarium fujikuroi, an industrial fungus used for gibberellin production. In this species, carotenoid-overproducing mutants, affected in the regulatory gene carS, exhibit an upregulated expression of the NX pathway. Based on former data on a stimulatory effect of nitrogen starvation on carotenoid biosynthesis, we developed culture conditions with carS mutants allowing the production of deep-pigmented mycelia. With this method, we obtained samples with ca. 8 mg NX/g dry mass, in turn the highest concentration for this carotenoid described so far. NX-rich extracts obtained from these samples were used in parallel with carS-complemented NX-poor extracts obtained under the same conditions, to check the antioxidant properties of this carotenoid in in vitro assays. NX-rich extracts exhibited higher antioxidant capacity than NX-poor extracts, either when considering their quenching activity against [O2(1Δg)] in organic solvent (singlet oxygen absorption capacity (SOAC) assays) or their scavenging activity against different free radicals in aqueous solution and in liposomes. These results make NX a promising carotenoid as a possible feed or food additive, and encourage further studies on its chemical properties.

Controlled Transcription of Regulator Gene carS by Tet-on or by a Strong Promoter Confirms Its Role as a Repressor of Carotenoid Biosynthesis in Fusarium fujikuroi

“…The fine regulation of carotenogenesis by the CarS protein in F. fujikuroi and its connections with the control by light is an intriguing scientific issue with potential biotechnological applications. Because of its antioxidant properties [ 4 ], NX is an attractive product for biotechnologists, and the understanding of the molecular mechanism that controls its synthesis in this fungus may have future applications. In this respect, the understanding of the posttranscriptional mechanisms governing carS function will be of particular interest in future research.…”

“…The latter include many fungi, which can produce and accumulate high levels of carotenoids [ 2 ]. This ability is of biotechnological importance, because some carotenoids perform critical functions in animals and humans, being the source of different biological molecules and having beneficial antioxidative properties [ 3 , 4 ]. Because animals and human are not able to synthetize carotenoids, they must obtain them in the diet [ 5 ].…”

Carotenoids, Vitamin C, and Antioxidant Capacity in the Peel of Mandarin Fruit in Relation to the Susceptibility to Chilling Injury during Postharvest Cold Storage

“…Determination of the DPPH• assay was performed as described in Parra-Rivero et al [ 38 ] with slight modifications. In a 96-well microplate, 10 µL of the sample extract were mixed with 290 µL DPPH• methanolic solution (100 µM) and allowed to stand for 30 min at room temperature in complete darkness.…”

“…For the FRAP assay, the procedure described by Parra-Rivero et al [ 38 ] adapted for flavedo tissue was followed. First, a reagent was prepared with 2,4,6-tri(2-pyridyl)-1,3,5-triazine (10 mM), acetate buffer (300 mM) and a ferric chloride solution (20 mM) (1:10:1, v : v : v ).…”

Metabolic engineering of Neurospora crassa for increasing carotenoids synthesis

“…The rising market demand of the various classifications of carotenoids has stimulated the development of its diverse production methods. Although current titers in many engineered fungi hosts except Fusarium fujikuroi (Parra-Rivero et al, 2020) still lack economic feasibility, future research leading to better approach in alternative hosts may be established for large scale production with less cost.…”