Altering operational conditions during protein fermentation to volatile fatty acids modifies the associated bacterial community.

Carlota Vijande, Riccardo Bevilacqua, Sabela Balboa, Marta Carballa
Author Information
  1. Carlota Vijande: CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela, Santiago de Compostela, Spain. ORCID
  2. Riccardo Bevilacqua: CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
  3. Sabela Balboa: CRETUS, Department of Microbiology and Parasitology, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
  4. Marta Carballa: CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.

Abstract

In recent years, the production of volatile fatty acids (VFA) through mixed culture fermentation (MCF) has been gaining attention. Most authors have focused on the fermentation of carbohydrates, while other possible substrates, such as proteins, have not been considered. Moreover, there is little information about how operational parameters affect the microbial communities involved in these processes, even though they are strongly related to reactor performance and VFA selectivity. Hence, this study aims to evaluate how microbial composition changes according to three different parameters (pH, type of protein and micronutrient addition) during anaerobic fermentation of protein-rich side streams. For this, two continuous stirred tank reactors (CSTR) were fed with two different proteins (casein and gelatine) and operated at different conditions: three pH values (5.0, 7.0 and 9.0) with only macronutrients supplementation and two pH values (5.0 and 7.0) with micronutrients' supplementation as well. Firmicutes, Proteobacteria and Bacteroidetes were the dominant phyla in the two reactors at all operational conditions, but their relative abundance varied with the parameters studied. At pH 7.0 and 9.0, the microbial composition was mainly affected by protein type, while at acidic conditions the driving force was the pH. The influence of micronutrients was dependent on the pH and the protein type, with a special effect on Clostridiales and Bacteroidales populations. Overall, this study shows that the acidogenic microbial community is affected by the three parameters studied and the changes in the microbial community can partially explain the macroscopic results, especially the process selectivity.

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Grants

  1. ED431C-2021/37/Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia
  2. ERA-IB-16-052/Agencia Estatal de Investigación
  3. PCIN-2016-102/Agencia Estatal de Investigación
  4. TED2021-130289B-I00/Agencia Estatal de Investigación

MeSH Term

Fatty Acids, Volatile
Fermentation
Bioreactors
Hydrogen-Ion Concentration
Bacteria
Anaerobiosis
Proteins
Biota
Microbiota

Chemicals

Fatty Acids, Volatile
Proteins

Word Cloud

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