Expanding the product spectrum in mixed-culture fermentation of organic solid waste through operational control

Abstract

The microbial synthesis of value-added biochemicals offers an attractive, sustainable alternative to conventional production methods. This study investigates mixed-culture fermentation (MCF) of the organic fraction of municipal solid waste (OFMSW) under varying operational conditions (temperature, pH, and hydraulic retention time (HRT)). The aim was to improve the production of selected carboxylates, including succinate and caproate. Furthermore, by assessing the metabolic roles of identified taxa and their responses to different process conditions, potential functional links between community composition and product formation were proposed. Under mesophilic conditions (37 °C), shifts in pH and HRT strongly influenced product distribution: succinate and propionate predominated at shorter HRTs, whereas caproate production prevailed at pH 6.5–7.0, 37 °C, and HRT of 5 days, reaching 515 mM C. Thermophilic (50 °C) operation favored the synthesis of ethanol, lactate, and butyrate. These findings demonstrate how operational strategies and microbial community dynamics can be leveraged to tailor product spectra in MCF.