The invention relates to the development of a novel medium starting from fresh water using a salt solution complex comprising a non conventional salt, namely KCl and conventional salts such as NaCl and MgSO.sub.4 in the proportion defined in the specification to generate biomass of higher carotenogenesis in particular Betacarotene and its isomers using Dunaliella salina ARL5 in a single stage of active growth. D.salina ARL5, a local isolate, has an unique property of having a wide range of pH an...