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Comparison of two different kinds of seed sludge and characterization of microorganisms producing hydrogen and soluble metabolites from raw glycerol

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Brazilian Journal of Chemical Engineering Aims and scope Submit manuscript

Abstract

Glycerol is a by-product generated in the biodiesel industry and can be converted by biological processes into products such as hydrogen, alcohols and acids. This study aimed at comparing two sources of inoculum in dark fermentation using raw glycerol and at identifying the microorganisms present by high-performance sequencing. Granular sludge obtained from a vegetable oil industry (VOI) and anaerobic sludge from a wine industry (WI) were evaluated in batch reactors with raw glycerol. The highest hydrogen yield was obtained for VOI (1.12 mol H2 / mol glycerolconsumed). The WI was more efficient in producing soluble metabolites, with 6.2 g / L of 1,3 – propanediol, ethanol (2.5 g / L) and acids (122 mg / g glycerolconsumed). Both assays consumed more than 60% of the glycerol. A significant variation in microbial diversity was observed between the beginning and the end of the fermentation. The microbial community showed a predominance of Firmicutes and the Clostridiaceae and Peptostreptococcaceae families in different abundances among the inocula, which could lead to an increase in hydrogen production or a higher concentration of metabolites. Clostridium bifermentans was the only species isolated, showing a yield of H2 (0.135 mol H2 / mol glycerolconsumed) and the main metabolite produced was ethanol (670 mg / L). These results showed that two different kinds of seed sludge can lead to different metabolic profiles from the same substrate, highlighting the importance of choosing the inoculum and, consequently, that the knowledge regarding microorganisms can direct the process towards products of industrial interest and contribute to the generation of sustainable energy.

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Data availability

The data used to support the findings of this study is available upon request.

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Acknowledgements

We thank High-Performance Computing Lab—LAD/PUCRS for allowing access to run the high-throughput sequence analyses.

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AS designed the study, analyzed the data and wrote the paper; LGA and DA carried out the experiments and analyzed the data; FEV analyzed the data and wrote the paper; LM, LGB and AG performed bioinformatics analyses and modified the manuscript; SP wrote the paper and supervised the research.

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Correspondence to Suelen Paesi.

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The authors declare no conflict of interest.

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This article does not contain any studies with human participants or animals performed by any of the authors.

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The authors declare to have participated in the study and authorize its publication without personal financial interests.

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All authors approved the manuscript and agree to the submission to the Brazilian Journal of Chemical Engineering.

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Paesi, S., Schiavenin, A., Almeida, L.G. et al. Comparison of two different kinds of seed sludge and characterization of microorganisms producing hydrogen and soluble metabolites from raw glycerol. Braz. J. Chem. Eng. 39, 387–402 (2022). https://doi.org/10.1007/s43153-021-00212-4

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  • DOI: https://doi.org/10.1007/s43153-021-00212-4

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