Susceptibility of biodiesel from tallow to biodegradation by Pseudallescheria boydii

Abstract

The characteristics of biodiesel produced can affect its susceptibility to biodegradation by microbial action, which has been of frequent concern since it leads to changes of fuel properties during storage. The goal of the present work was to compare the microbial growth in biodiesel obtained from tallow catalyzed by NaOH or KOH and purified with water or the solid adsorbent magnesium silicate. The experiment was carried out in 200 mL glass bottles containing 45 mL of mineral medium and 5 mL of each type of biodiesel (4 treatments) and 104 spores.mL­–1 of the filamentous fungi Pseudallescheria boydii. The analyses were carried out during 60 days and after each 10 days it was evaluated: fungi biomass formation (dry weight); production of metabolites originated from the fungi growth (pH); variation in the amount of total esters and total glycerol in the oily phase. After 60 days it was possible to observe lower biomass formation in the biodiesel NaOH-water (576 mg) followed by biodiesel NaOH-magnesol (773 mg). The biodiesel KOH-magnesol and KOH-water favored the biomass formation (891 mg and 930 mg respectively).