The effect of substrate concentration on granular fermentation for caproic acid production

Quinten Mariën

doi:10.18174/icec2020.18028

Abstract

Contribution to the International Chain Elongation Conference 2020 | ICEC 2020. An abstract can be found in the right column.

Highlights

Todays increasing organic waste production poses a challenge for the conversion of liquid waste streams into added-value products beyond non-profitable methane and ethanol-based medium chain carboxylic acids (MCCA)
RESULTS & DISCUSSION: In a first part, diluting the thin stillage (44.15 ± 2.64 gCOD·L-1) to respectively 75%, 50% and 25% of the original COD content resulted in a decrease in C6 concentration in the effluent while the selectivity with which C6 was produced, remained constant at 48 ± 3% (COD of C6 relative to all produced carboxylic acids) (Figure 1)
The highest amounts of total biomass were consistently found at the lowest substrate concentrations and substantial growth of the granular bed was observed at lower substrate concentrations. This suggests that substrate limitation and/or concomitant low C6 concentrations may have a positive impact on biomass aggregation, but the mechanism remains unclear

Summary

Introduction

Todays increasing organic waste production poses a challenge for the conversion of liquid waste streams into added-value products beyond non-profitable methane and ethanol-based medium chain carboxylic acids (MCCA). Lactic acid chain elongation to produce caproic acid (C6) has gathered an increasing amount of attention due to its potential in coupling lactic acid production from carbohydrates to chain elongation, thereby eliminating the need for exogeneous addition of electron donors[1,2]. To date these systems, still struggle with rate limitations, a key barrier that had been identified early on in the new wave of MCCA-research of the 2010s3. The aim of this study was to shed light on the effect of substrate concentration, with solids-free thin stillage as feedstock, on granular fermentation in expanded granular sludge bed (EGSB) reactors

Objectives

Results

Conclusion