Comprehensive evaluation of starter culture impact on the bioreactor performance and microbial kinetics

The present study investigated the disregarded impact of microbial community composition, diversity and abundance of the starter biomass on lab-scale bioreactor performance, steady-state long time operation, biodegradation outcome and microbial kinetics. Standard lab-scale experiments are usually initiated with inoculum taken from wastewater treatment plants (WWTPs) without considering microbial community composition. Two identical sequencing batch bioreactors (SBR-1, SBR-2) were operated with inocula obtained from two domestic WWTPs to assess the role of inoculum composition on reactor performance and treatment efficacy. Filamentous microorganisms were dominated in SBR-1 (SVI: 265 mL/g), whereas their supremacy was diminished in SBR-2 (SVI: 160 mL/g). Next generation sequencing analyses verified high abundance of Candidatus Microthrix (14%) and Kouleothrix spp. (3%) in SBR-1. Although Chloroflexi C10-SB1A metagenome accounted for 16% of WWTP-2 community, SBR-2 was operated at steady-state for longer period without deterioration. Statistical indicators based on molecular studies showed that WWTP-2 has higher diversity than WWTP-1. Higher biodiversity in WWTP-2 community supported the stable process performance. Modelling studies denoted an increase in half saturation coefficients (K_s) in filamentous microorganisms dominated reactor. The results of this study provide insight on how the filamentous organisms typically found in WWTPs become a fundamental constituent during the bioreactor operation.