Fig. 6

Linear Pearson correlation analysis of on-line measurements with parameters related to acidogenesis from both PFRs during continuous fermentation over 123 weeks (weekly average values). Correlation coefficients ≥ 0.7 are marked for visualization of the location-dependent correlation pattern. Excluded data points: start-up phase (W1–W6, W20–PFR2), first week of 7 d HRT (W9–PFR1). SCCA short-chain carboxylic acids, BA butyric acid, LA lactic acid, AY acid yield