Abstract

The acido-and thermophilic red alga Galdieria sulphuraria (Galdieri) Merola grows under mixo- and heterotrophic conditions on 27 different sugars and sugar alcohols as sole carbon source. We separated two strains from an isolate originally collected at Mt. Lawu (Indonesia). These strains are indistinguishable in growth and pigmentation under autotrophic conditions. However, under heterotrophic conditions, strain 074 W lost most of its pigments whereas strain 074 G stayed green on all substrates tested. Strain 074 G had the highest pigment content when grown on sugar alcohols. Usually the alga exhibited a short lag-phase followed by logarithmic growth. However, when transferred from auto- to heterotrophic conditions a lag-period of about 45 days was observed with the sugar alcohol dulcitol. Similarly, long lag-periods were also noticed for strain 074 G grown on D-mannitol and for strain 074 W grown on D-ribose. The length of the lag-phase is a function of the length of the previous culture under autotrophic conditions. This enormous versatility in the heterotrophic growth of Galdieria sulphuraria presents an ideal system to study the metabolism of rare sugars and sugar alcohols.

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