Growth yield from electrons available from substrates in aerobic- and photoheterotrophic cultures of Rhodopseudomonas sphaeroides S

A balance of electrons available from acetic acid consumed for growth and oxygen uptake in the aerobic- and photoheterotrophic growth of Rhodopseudomonas sphaeroides S on acetate-minimal medium could be realized the same as in the carbon balance. The unmeasured amounts of yeast extract consumed by the cells grown on propionate–yeast extract media were indirectly estimated from the balance equation of electrons available from carbon substrates. The specific consumption rate of the yeast extract increased with an increase in propionate consumption rate in aerobic and photoheterotrophic cultures. Growth yields from acetic acid and from propionic acid plus yeast extract were calculated on the electron level, i.e., Y_X/ave g cell produced/equivalent electrons available from substrate consumed. Y_X/ave values were 5.0 to 5.8 g cell/ave in photoheterotrophic cultures and 2.7 to 3.6 in aerobic–heterotrophic cultures regardless of different medium compositions.