Mannitol Production by Pyrenochaeta terrestris

Abstract

Abstract Pyrenochaeta terrestris (Hansen) Gorenz, J. C. Walker and Larson produces D‐mannitol in the mycelium but not in the cutture filtrates when grown in a sucrose salts liquid medium.In the present study, P. terrestris was grown in stilt culture on a synthetic salts medium containing 30 g of sucrose per liter. After inoculation with a myceliat suspension, the mycelial mats were harvested and the dry weight and the amount of mannitol were determined. Maximum mycelial mat production occurred at 15 days after inoculation while the amount of mannitol was greatest at about 7 days after inoculation. The percentage of mannitot on a dry weight basis was maximal (20–25 per cent) within a few days after inoculation and decreased rapidly to 3–4 per cent at the time mycelial mat production was greatest. The same percentage of mannitot was produced when the fungus was grown in shake culture or when the sucrose was replaced by equivalent amounts of D‐fructose, D‐glucose, D‐mannose, maltose, trehalose, and raffinose. Increasing the amount of sucrose or decreasing the amount of sodium nitrate increased the amount of mycelium produced but the percentage of mannitol in the mycelium remained about the same.Mannitot was reutilized when mycelial mats were transferred to a mineral medium without a carbon source. It was concluded that mannitot probably serves as a reserve carbohydrate in P. terrestris.