https://pubmed.ncbi.nlm.nih.gov/2855583/
Pyrroloquinoline quinone: excretion by methylotrophs and growth stimulation for microorganisms
A marked excretion of pyrroloquinoline quinone (PQQ) by methylotrophs into the culture medium was observed when incubation was prolonged to the late stationary...
excretiongrowthstimulationmicroorganisms