Microbial growth in Acrocomia aculeata pulp oil, Jatropha curcas oil, and their respective biodiesels under simulated storage conditions

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. (C) 2016 BRTeam. All rights reserved.