Kinetic comparisons of mesophilic and thermophilic aerobic biomass

Abstract

Kinetic parameters describing growth and decay of mesophilic (30°C) and thermophilic (55°C) aerobic biomass were determined in continuous and batch experiments by using oxygen uptake rate measurements. Biomass was cultivated on a single soluble substrate (acetate) in a mineral medium. The intrinsic maximum growth rate (μmax) at 55°C was 0.71 ± 0.09 h-1, which is 1.5 times higher than the μmax at 30°C (0.48 ± 0.11 h-1). The biomass decay rates increased from 0.004 h-1 at 30°C to 0.017 h-1 at 55°C. Monod constants were very low for both types of biomass: 9 ± 2 mg chemical oxygen demand (COD) l-1at 30°C and 3 ± 2 mg COD l-1at 55°C. Theoretical biomass yields were similar at 30 and 55°C: 0.5 g biomass COD (g acetate COD)-1. The observed biomass yields decreased under both temperature conditions as a function of the cell residence time. Under thermophilic conditions, this effect was more pronounced due to the higher decay rates, resulting in lower biomass production at 55°C compared to 30°C.