Promotion of Acetic Acid Fermentation by Pyrroloquinoline Quinone

The acetic acid fermentation was largely accelerated by the addition of pyrroloquinoline quinone, PQQ, into the culture medium. As has been previously known that PQQ has a unique biological activity to shorten the lag phase in microbial growth yielding the subsequent growth stimulation, the addition of PQQ to the culture medium supported the growth stimulation and resulted in enhanced enzyme formation of both membrane-bound alcohol and aldehyde dehydrogenases, which are directly catalyzing acetic acid formation. Oxidation of ethanol to acetic acid by these enzymes caused a rapid accumulation of acetic acid in the culture medium. Thus, the addition of PQQ was turned out to be useful to improve the productivity of acetic acid fermentation in saving inoculum required to the next batch. It was also clarified that glycerol contributed to acetic acid fermentation by becoming a good carbon source for cell growth.