Selection of filamentous fungi for conversion of high concentrations of biodiesel-derived glycerin

Biodiesel-derived glycerin is a potential biotechnological substrate, but its bioconversion depends on finding resistant microbial strains, once this effluent can be inhibitory for growth. A total of 58 microbial isolates from 26 samples of soil, rotten leaves, and other fallen plant materials or contaminated foods, survived an enrichment selection performed at 25% of biodiesel-derived glycerin. Aspergillus sp. T7.1, Penicillium sp. T2.1 and T6.2 grew in submerged processes adjusted for citric acid production, at a final concentration of 100 g . L-1 of glycerol derived from biodiesel as carbon source (1.1 M). Under these conditions, isolates T7.1 and T2.1 produced limited amounts of acid, but consumed 50% and 40% of the initial glycerol, at volumetric consumption rates of 0.3 g . L-1 . h-1 and 0.24 g . L-1 . h-1, respectively. Another isolate, Penicillium sp. T14.1 showed high index of acidogenesis in solid media and resisted to 3 M biodiesel-derived glycerol under submerged cultivation, producing 5 times more acid than the above strains. Results indicate the genus Penicillium as a good source of microbial agents for use of glycerin effluent.