Abstract

Carotenoids are essential nutrient compounds with numerous biological functions. Neurospora crassa is a model filamentous fungus with orange pigmentation which is attributed to the accumulation of carotenoids containing neurosporaxanthin (NX) and neutral carotenoids (NC). To enhance carotenoids synthesis in N. crassa, isoprene diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) were increased using the genes, xylulose-5-phosphate phosphoketolase (XPK), phosphotransacetylase (PTA), and NADH-specific-3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMGR), as single, fused and three combined expressions to channel more carbon source into the mevalonate pathway (MVP). The single (PTA, XPK, HMGR), fused (PTA:HMGR & XPK:HMGR) and three combined gene (PTA with fused XPK:HMGR) expressions in engineered fungal resulted in carotenoid titers with contents of NX accumulated up to 4.5 mg/g DW and NC up to 1.7 mg/g DW as compared to the wild-type with NX up to 1.54 mg/g DW and NC up to 0.8 mg/g DW. The optimized MVP with metabolic engineering methods is a key method to increase the synthesis of carotenoid and other active terpenoids in N. crassa.

Key words: Neurospora crassa, mevalonate pathway, carotenoids, neurosporaxanthin, neutral carotenoids.