Citric Acid Accumulation from Sugar Beet Molasses by 2- Deoxyglucose and Manganese Resistant Fungal Strains

摘要

The present investigation deals with improvement of citric acid production by some induced mutant strains and protoplast fusion from the intergeneric fusant (3/16) using beet molasses. UV irradiation followed by selection and then by EMS treatments with different exposure times and concentrations and selection on different concentrations of manganese and 2-deoxyglucose were applied. Two UV-mutants (A/DG/6 and B/DG/4) obtained from the first mutation step proved to be more efficient in accumulating citric acid (162.8 % and 160.5 % from the original strain 3/16, respectively). Moreover, one EMS-mutant (500/50/30/9), obtained from the second step, showed the highest citric acid productivity (227.9 % from the original strain 3/16). After the application of protoplast fusion between certain new mutants, 15 fusants were isolated and tested for their citric acid production. Two fusants (F10 and F15) produced 255.8 % citric acid from the original strain (3/16). On the other hand, since all fusants showed differences in DNA content, the highest fusants in citric acid accumulation showed highest DNA contents whereas, fusant F9 produced citric acid less than the higher parent but showed highest DNA content. Moreover, fusant F12 contained highest DNA however, it is produced at the same higher parent. Furthermore, results obtained proved that even citric acid productivity and DNA content were not correlated; however, the productivity depends on specific DNA content.