Coproduction of single cell protein and pyrroloquinoline quinone by Hyphomicrobium denitrificans using molasses and biogas slurry.

Single cell protein (SCP) is an important supplement to animal protein feed, and pyrroloquinoline quinone (PQQ) is frequently used as a functional food and animal feed ingredient. In this study, we aimed to coproduce SCP and PQQ through the fermentation of molasses and biogas slurry by Hyphomicrobium denitrificans SSWJ1 (H. denitrificans SSWJ1). We evaluated the tolerance of H. denitrificans SSWJ1 to alkaline conditions, revealing optimal growth at pH 8, and compared the SCP amounts synthesized in molasses and biogas slurry media (2.0 g/L) and in methanol and ammonium sulfate media (0.7 g/L). We proposed a two-stage oxygen delivery approach, which yielded 35.6 g/L SCP and 235.1 mg/L PQQ in a 5-L fermenter. This study presents a highly efficient strategy of coproducing SCP and PQQ from molasses and biogas slurry, could be used for the sustainable production of alternative animal proteins and generation of high-value products from wastewater.