In the biosynthesis of antibiotics problems regarding the uses of plant raw materials very often arise. Due to their large quantities - from 50% in Tetracycline to 90% in Penicillin, it is important that the most reliable plant raw material for processing is used. A pilot installation was created with which the relations between quality of maize hybrids, their corn steep liquor and the results of their use in biosynthesis of Tetracycline was studied. Full scale research as per standards, and additional investigations from amino acids in maize and corn steep liquor has been conducted. Our results show that it is possible to obtain about 70% higher activity in the process of biotechnological manufacture of Tetracycline in comparison with the control sample obtained from the most widespread. Bulgarian corn steep liquor. Keywords : plant raw material, biosynthesis of antibiotics corn steep liquor, maize hybrids