The magnetic properties and hyperthermia effect were studied in solution of magnetosomes obtained by changing conditions during biomineralization of magnetotactic bacteria Magnetospirillum sp.AMB-1. It was shown that adding a higher amount of Wolfe's vitamin solution (WVS) or ferric quinate (FQ) cause increase of the mean diameter from 47 nm (normal condition) up to 52 nm and 58 nm respectively. As a consequence of this change the preparation conditions coercivity and Specific Absorption Rate (SAR) increased up to 20 Oe and 949 W/gFe for sample FQ, respectively. On the other hand the process of cultivation at the changed conditions markedly reduced the cultivation time. Also the isolated chains of magnetosome were shorter containing less amount of magnetosomes too.