A Flexible System for Cultivation ofMethanococcusand Other Formate-Utilizing Methanogens

Abstract

Many hydrogenotrophic methanogens use either H2or formate as the major electron donor to reduce CO2for methane production. The conventional cultivation of these organisms uses H2and CO2as the substrate with frequent replenishment of gas during growth. H2is explosive and requires an expensive gassing system to handle safely. Formate is as an ideal alternative substrate from the standpoints of both economy and safety but leads to large changes in the culture pH during growth. Here, we report that glycylglycine is an inexpensive and nontoxic buffer suitable for growth ofMethanococcus maripaludisandMethanothermococcus okinawensis. This cultivation system is suitable for growth on liquid as well as solid medium in serum bottles. Moreover, it allows cultivation of liter scale cultures without expensive fermentation equipment. This formate cultivation system provides an inexpensive and flexible alternative for the growth of formate-utilizing, hydrogenotrophic methanogens.