Effects of extremely low frequency magnetic field on production of mannatide by [alpha]-hemolytic Streptococcus

The effect of the extremely low frequency magnetic field (ELF-MF) on biomass and mannatide production by [alpha]-hemolytic Streptococcus in liquid-state fermentation culture medium was studied during shake flask culture. Magnetic field (MF) inductions, exposure times, and exposure periods varied in a range of 0-1.5mT, 0-16h, and six periods of incubation time, respectively. Results showed both biomass and mannatide production increased significantly at MF induction 0.4, 0.6, and 0.9mT and decreased at both 1.2 and 1.5mT. Biomass increased by exposure for initial and middle stages of fermentation. Mannatide production increased significantly at 4-8, 8-12, and 17-21h. Peak yield of biomass and mannatide production increased by 10.7% and 14.0% at 25 and 27h of incubation at 0.6 mT MF induction and exposure to 8-12h of incubation time, compared with the control experiment, respectively. ELF-MF could also enhance the growth rate and mannatide production rate of [alpha]-hemolytic Streptococcus. However, ELF-MF did not alter [alpha]-hemolytic Streptococcus cell growth and mannatide metabolizing regulation or fermentation pattern. Mannatide production was not associated with cellular growth but rather only partially associated. Bioelectromagnetics. 37:331-337, 2016. © 2016 Wiley Periodicals, Inc.