Seaweeds contain a variety of biologically active substances, which are useful for therapy and medicinal purposes. Brown algae Endarachne binghamiae (Phaeophyceae) as well-balanced, harmless, natural sources with a high degree of bioavailability of trace elements are strongly advised for fast grown children and pregnant women. We survey different factors affecting to hydrolysis of brown algae to produce mannitol. Our results are as follows: H2SO4 concentration 2%; steaming time 30 minutes; substrate 1.5%; enzyme Cellic 20% – Cellulase 12% – AMG 2%; pH 5; incubation temperature 38 oC.