Figure 1

F. succinogenes growth and pH control after random mutagenesis. When the chemostat culture of wild-type F. succinogenes was grown in steady state in cellobiose medium at pH 6.25, mutagen NTG was added to induce random mutations. The pH and medium feed control units were carefully controlled to maintain viability of the culture and to screen for acid tolerant populations. As pH (red) decreased over time, the OD readings in blue shows culture adaptation to low pH stress accordingly. The mutant populations went through three major adjustments and finally reached steady state at pH 5.75. The selected culture was later confirmed to have the ability to tolerate a pH between 5.60 and 5.65 in batch culture.