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 MgSO₄ 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 and temperature tolerance which is beneficial in production terms as it is grown in external conditions (i.e. outdoors).