Quantification of Biomass and Metabolites

Biomass yield was determined by measuring the corresponding percentage packed biomass volume (PMV %), as obtained after centrifugation of a 6-ml culture sample at 4000 rcf, for 10 min, at 4 °C. Glucose concentration in the medium was evaluated by using a GM8 MicroStat analyzer (Analox) and the appropriate reagent, following manufacturer’s instructions. The pH value of the medium was measured using a 1-ml sample of spent medium and a Mettler-Toledo FiveGo pH-meter. The presence of NAI-107 congeners in the extracts was verified by LC-MS analysis and by microbiological assays as previously described [58 (link)]. Ammonia and Pi content in the medium was spectrophotometrically determined by Nessler reagent [67 (link)] and ammonium molybdate method [68 (link)], respectively. The Po content was measured as the increment of medium Pi content due to acid-hydrolysable phosphate released from organic sources after a treatment of spent medium aliquots with 5.25 N H₂SO₄ (1:12.5 v/v) in boiling water bath (30 min.) and subsequent neutralization with 5 N NaOH (1:10 v/v).