Flocculation of Aspergillus terreus with polyelectrolyte complex and production of itaconic acid with the flocculated mycelia

Mycelia from Aspergillus terreus K 26 were flocculated with a polyelectrolyte complex consisting of potassium poly9vinyl alcohol) sulfate (KPVS) and poly(diallyldimethyl-ammonium chloride) (PDDA) by three different methods: (a) PDDA was added into the broth obtained from precultivation of the hyphal inoculum in the presence of KPVS; (b) use of KPVS and PDDA was reversed from that in method a; (c) after the precultivation in the absence of the polymer, the mycelia were harvested, dispersed in 0.1 M phosphate buffer containing PDDA, then flocculated by addition of KPVS. The three types of the flocculated mycelia were investigated concerning growth and itaconic acid production in shake flask cultures. Viscosity and sedimentation were further examined to characterize the flocculated mycelial broths. A slight inhibition caused by flocculation on growth and acid production was observed at the beginning of repeated cultivation, but this was eliminated when cultivation in the fresh medium was repeated. There was no marked difference in the specific rates of acid production between fre and flocculated cells. Viscosity of the flocculated mycelial system was close to that of the medium, even while maintaining a cell concentration of 2 g/dl. The poor sedimentation of mycelia was favorably imporved with these flocculation methods, especially with methods b and c.