Protein composition determines the preferential consumption of amino acids during anaerobic mixed-culture fermentation. (15th September 2020)

• Record Type: Journal Article
• Authors: Bevilacqua, Riccardo; Regueira, Alberte; Mauricio-Iglesias, Miguel; Lema, Juan M.; Carballa, Marta
• Is Part Of: Water research. Volume 183(2020)
• Publication Date: 2020-09-15
• Subjects: Acidification -- Biorefinery -- Productivity -- Protein composition -- Selectivity -- Volatile fatty acid production; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115958
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: The valorisation of protein-rich residual streams by anaerobic mixed-culture fermentation (MCF) has been barely studied in contrast to carbohydrate-rich wastes. The aim of this work was, therefore, to investigate how protein composition, i.e. the amino acid (AA) profile, affects the individual consumption of amino acids and, consequently, the outcome of the process. Mixed-culture fermentations were performed with two model proteins (casein and gelatin) using continuous and batch reactors at neutral pH values and 25 °C. The acidification was incomplete for both proteins, with casein achieving a higher value than gelatin. Albeit dominated by acetic acid, product spectra were different as well, with n-butyric acid as the second major product for casein and propionic acid for gelatin. The preferential consumption of amino acids was demonstrated, which interestingly depends on protein composition. The previously accepted stoichiometry accurately describes iso and n-butyric acid production, but it fails for propionic, iso and n-valeric acid generation. Overall, this study offers a better understanding of protein fermentation mechanisms, which will help to improve degradation models and to design fermentation processes, based on optimal substrate selection. Graphical abstract: Image 1 Highlights: Protein fermentation generally results in incomplete acidification. Balanced amino acid redox roles do not guarantee higher acidification degrees. The preferential consumption of amino acids was demonstrated. Protein composition affects acidification, selectivity and preferential consumption. The accepted stoichiometry is not sufficient to describe protein conversion to VFA.