Evaluation of protein composition influence on yields and selectivity of volatile fatty acids production

Abstract

The influence of protein composition on volatile fatty acids (VFA) production is not clear and need to be further studied to valorise protein residual streams. For this purpose, two continuous stirred tank reactors were inoculated with acidogenic biomass and fed with two proteins (casein and gelatin) having different amino acids compositions. Casein showed a higher acidification degree and double the VFA productivity of gelatin, despite its imbalance between electron acceptor amino acids and donors. Experimental VFA spectra highlighted n-butyric acid as a major product for casein and propionic acid for gelatin. Finally, we hypothesised preferential consumption for some amino acids (AA), with the experimental results confirming it. For this reason, previous models based on fixed Stickland stoichiometry could be inaccurate at describing proteins degradation. This knowledge helps to better predict the outcome of the process when fermenting protein rich substrates