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Front. Microbiol. | doi: 10.3389/fmicb.2018.01388

Assessing the effect of pretreatments on the structure and functionality of microbial communities for the bioconversion of microalgae to biogas

 Olivia Córdova1*, Rolando Chamy1, Lorna Guerrero2 and  Aminael Sánchez-Rodríguez3*
  • 1Pontificia Universidad Católica de Valparaíso, Chile
  • 2Federico Santa María Technical University, Chile
  • 3Universidad Técnica Particular de Loja, Ecuador

Microalgae biomethanization is driven by anaerobic sludges and generally limited by the incomplete hydrolysis of the wall of these organisms and therefore, by the low availability of microalgal biomass for the methanogenic community. The application of enzymatic pretreatments, e.g. hidrolytic enzymes, is among the strategies used to work around this limitation. Despite these pretreatments proven efficiency in increasing biomethanization, the changes that a given pretreatment may cause to the structures of microbial communities, i.e. functionally active species, of anaerobic sludge during biomethanization are still unknown. This study evaluated the changes in the expression of the metatranscriptome of microalgae communities of anaerobic sludge during the biomethanization of Chlorella sorokiniana without pretreatment (control) and pretreated with cellulase in order to increase the solubilization of organic matter. Pretreated microalgal biomasses experienced significant increases in the production of biogas. At the level of the metatranscriptome, the control samples showed that the microalgae cells are functionally active and that the methanogenic community is dominated by γ- and δ- proteobacteria, such as Methanospirillum hungatei. In contrast, the pretreated samples were characterized by the absence of active microalgae cells and a bacteria population dominated by species of the Clostridia class. These differences are also related to the differential activation of metabolic pathways/routes associated with the degradation of organic matter to its biomethanization.

Keywords: Biogas, Microalgae, Chlorella, Methane, bioconversion, Enzymatic pretreatment

Received: 02 Feb 2018; Accepted: 06 Jun 2018.

Edited by:

Diana E. Marco, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina

Reviewed by:

Jiangxin Wang, Shenzhen University, China
Seung Gu Shin, Pohang University of Science and Technology, South Korea  

Copyright: © 2018 Córdova, Chamy, Guerrero and Sánchez-Rodríguez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Olivia Córdova, Pontificia Universidad Católica de Valparaíso, Valparaiso, Chile,
Dr. Aminael Sánchez-Rodríguez, Universidad Técnica Particular de Loja, Loja, Ecuador,