Statistical correlation between waste macromolecular composition and anaerobic fermentation temperature for specific short-chain fatty acid production

Abstract

To properly exploit short-chain fatty acids (SCFAs) in the chemical industry, it is of foremost importance to ensure stable SCFA profile production via anaerobic fermentation (AF). The different macromolecular distribution of food wastes (FWs) used as feedstock might be crucial for process outcome. Targeting at a specific SCFAs profile and yield, this study explored the statistical correlation between the macromolecular composition of FWs and the produced SCFAs in batch-AFs at 25 °C and 55 °C. Principal Component Analysis (PCA) revealed that the carbohydrates fraction was directly related with butyric acid accumulation, regardless of process temperature. Nevertheless, operational temperature resulted in a pH change, which ultimately affected the process fate. PCA of 25 °C-batch-AF showed a positive correlation between high carbohydrate content and longer-chain acids accumulation. By contrast, 55 °C-AF resulted in higher product specificity than at 25 °C, mainly due to butyrate-type fermentation of carbohydrates. Batch results were further validated in a semicontinuous reactor. Prevailing SCFAs and high bioconversion efficiencies relied on 3 main FWs characteristics: high carbohydrate content (>77% w/w), high carbohydrate/protein ratio (≥10) and high soluble organic matter content. Results obtained herein allowed predicting a specific SCFAs profile based on FWs composition, which is relevant for setting proper downstream technologies.