A simple and efficient method for the extraction and separation of menaquinone homologs from wet biomass of Flavobacterium.

Menaquinone homologs (MK-n), that is, MK-4, MK-5, and MK-6, can be produced by the fermentation of Flavobacterium. In this study, we proposed a simple and efficient method for the extraction of menaquinones from wet cells without the process of drying the biomass. Meanwhile, a rapid and effective solution for the separation of menaquinone homologs was developed using a single organic solvent, which was conducive to the recovery of the solvent. The results showed that the highest yield was obtained with pretreatment using absolute ethanol at a ratio of 6:1 (v/m) for 30 min and then two extractions of 30 min each using methanol at a ratio of 6:1 (v/m). The recovery efficiency of the menaquinones reached to 102.8% compared to the positive control. The menaquinone homologs were effectively separated using methanol as eluent at a flow rate of 0.52 mL/min by a glass reverse-phase C18 silica gel column with a height-to-diameter ratio of 5.5:1. The recovery of menaquinones achieved was 99.6%. In conclusion, the methods for extraction and separation of menaquinone homologs from wet Flavobacterium cells were simple and efficient, which makes them suitable not only on a laboratory scale but also for application on a large scale.