Document Type : Research Paper
Department of Microbiology, Federal University of Rio Grande do Sul. Rua Sarmento Leite, N° 500, 90050-170, Porto Alegre, RS, Brazil.
Corrosion and Degradation Division, National Institute of Technology, Av. Venezuela, Nº 82, Sala 608, 200081-312, Rio de Janeiro, RJ, Brazil.
Department of Inorganic Chemistry, Federal University of Rio Grande do Sul. Av. Bento Gonçalves, Nº 9500, 91501-970, Porto Alegre, RS, Brazil.
With increasing demands for biodiesel in Brazil, diverse oil feedstocks have been investigated for their potentials for biodiesel production. Due to the high biodegradability of natural oils and their respective biodiesels, microbial growths and consequent deterioration of final product quality are generally observed during storage. This study was aimed at evaluating the susceptibility of Acrocomia aculeata pulp oil and Jatropha curcas oil as well as their respective biodiesels to biodeterioration during a simulated storage period. The experiment was conducted in microcosms containing oil/biodiesel and an aqueous phase over 30 d. The levels of microbial contamination included biodiesel and oil as received, inoculated with fungi, and sterile. Samples were collected every 7 d to measure pH, surface tension, acidity index, and microbial biomass. The initial and final ester contents of the biodiesels were also determined by gas chromatography. The major microbial biomass was detected in A. aculeata pulp and J. curcas biodiesels. Significant reductions in pH values were observed for treatments with A. aculeata pulp biodiesel as a carbon source (p <0.05). The surface tension values decreased for all treatments (p <0.05). Total ester contents were decreased in A. aculeata pulp and J. curcas biodiesels when inoculated by fungi by approximately 8 and 12%, respectively, indicating the occurrence of biodegradation during the relatively short storage period of only 30 d.
- Microbial growth capacity of filamentous fungi in Acrocomia aculeata pulp oil and Jatropha curcas oil and their respective biodiesels investigated.
- Order of susceptibility to microbial growth was A. aculeata pulp Biodiesel > J. curcas Biodiesel > A. aculeata pulp oil > J. curcas oil.
- Esters contents of A. aculeata pulp and J. curcas biodiesels decreased by approx. 8 and 12% when inoculated by fungi.
- The occurrence of biodiesel biodegradation even during a relatively short storage period of only 30 d was observed.