This study describes the first successful method for producing ergot alkaloids in vitro using Sphacelia sorghi, a Nigerian fungus parasitic on sorghum. Researchers cultured an alkaloid-producing strain (strain A) in defined liquid medium and achieved yields exceeding 0.5 mg/ml of dihydroergosine, the principal alkaloid, along with smaller amounts of other ergot alkaloids. Alkaloid production occurred late in the growth phase, with most product released into the culture medium. The study revealed that changes in mycelial fatty acid composition during growth—specifically an increase in unsaturated 18-carbon fatty acids—correlated with development of sclerotium-like tissues. A non-alkaloid-producing strain (strain NA) showed different metabolic patterns, including asparaginase activity converting asparagine to aspartic acid. Both strains rapidly absorbed inorganic phosphate and utilized sucrose preferentially as glucose. An important technical observation was that glucan accumulated in alkaloid-producing cultures, limiting shake-culture feasibility. This work enables future studies on dihydrogenated ergot alkaloid biosynthesis and provides a source of dihydrolysergic acid for chemical synthesis of pharmaceutical compounds.

Key findings

• Surface liquid cultures of Sphacelia sorghi strain A produced dihydroergosine and related ergot alkaloids in yields exceeding 0.5 mg/ml, with peak accumulation of ~700 μg/ml by day 22 of fermentation
• Alkaloid synthesis occurred at the end of the growth phase, with most product released into the culture medium and increasing proportions retained in mycelium over time
• Changes in mycelial triglyceride fatty acid composition during growth—shift from saturated to unsaturated 18-carbon acids—were associated with development of sclerotium-like tissues similar to natural sclerotia
• The alkaloid-producing strain accumulated glucan throughout fermentation, whereas the non-alkaloid-producing strain produced only transitory glucan, suggesting different tissue development patterns
• Critical medium parameters for alkaloid production included L-asparagine as nitrogen source, sucrose as carbon source, optimal phosphate concentration (0.025% KH₂PO₄), and a pH of 5.5