Feasibility of sunflower oil cake degradation with three different anaerobic consortia

Abstract

Sunflower oil cake (SuOC) is the solid by-product from the sunflower oil extraction process and an important pollutant waste because of its high organic content. For the anaerobic digestion of SuOC three different industrial reactors were compared as inoculum sources. This was done using a biochemical methane production (BMP) test. Inoculum I was a granular biomass from an industrial reactor treating soft-drink wastewaters. Inoculum II was a flocculent biomass from a full-scale reactor treating biosolids generated in an urban wastewater treatment plant. Inoculum III was a granular biomass from an industrial reactor treating brewery wastes. The highest kinetic constant for methane production was achieved using inoculum II. The inoculum sources were analyzed through PCR amplification of 16S rRNA genes and fingerprinting before (t = 0) and after the BMP test (t = 12 days). No significant differences were found in the bacterial community fingerprints between the beginning and the end of the experiments. The bacterial and archaeal communities of inoculum II were further analyzed. The main bacteria found in this inoculum belong to Alphaproteobacteria and Chloroflexi. Of the Archaea detected, Methanomicrobiales and Methanosarcinales made up practically the whole archaeal community. The results showed the importance of selecting an appropriate inoculum in short term processes due to the fact that the major microbial constituents in the initial consortia remained stable throughout anaerobic digestion.

Keywords:

• Sunflower oil cake
• biochemical methane potential
• microbial community
• fingerprints
• methane yield
• kinetics

Acknowledgments

The authors wish to express their gratitude to “Junta de Andalucía” (“Plan Andaluz de Investigación”) for the financial support to groups BIO288 and AGR204, to the Spanish Ministry of “Ciencia and Innovación” (Project reference CTM2008-05772/ TECNO) and to the contracts JAE-Doc from “Junta para la Ampliación de Estudios del CSIC” co-financed by European Social Funds. The authors thank Dr. Fernando G. Fermoso for his valuable discussions during the preparation of the manuscript.