May 6/Journal of Farming -- "Crude glycerol is a major byproduct for the biodiesel industry. Producing value-added products through microbial fermentation on crude glycerol provides opportunities to utilize a large quantity of this byproduct," U.S. investigators report.
"The objective of this study is to explore the potential of using crude glycerol for producing eicosapentaenoic acid (EPA, 20:5 n-3) by the fungus Pythium irregulare. When R irregulare was grown in medium containing 30g/L crude glycerol and 10g/L yeast extract, EPA yield and productivity reached 90mg/L and 14.9mg/L.day, respectively. Adding pure vegetable oils (flaxseed oil and soybean oil) to the culture greatly enhanced the biomass and the EPA production. This enhancement was due to the oil absorption by the fungal cells and elongation of shorter chain fatty acids (e.g., linoleic acid and a-linolenic acid) into longer-chain fatty acid (e.g., EPA).
The major impurities contained in crude glycerol, soap and methanol, were inhibitory to fungal growth. Soap can be precipitated from the liquid medium through pH adjustment, whereas methanol can be evaporated from the medium during autoclaving.
The glycerol-derived fungal biomass contained about 15% lipid, 36% protein and 40% carbohydrate, with 9% ash. In addition to EPA, the fungal biomass was also rich in the essential amino acids lysine, arginine and leucine, relative to many common feedstuffs. Elemental analysis by inductively coupled plasma showed that aluminum, calcium, copper, iron, magnesium, manganese, phosphorus, potassium, silicon, sodium, sulfur, and zinc were present in the biomass, whereas no heavy metals (such as mercury and lead) were detected," wrote S.K. Athalye and colleagues, Virginia Polytechnic Institute.
The researchers concluded, "The results show that it is feasible to use crude glycerol for producing fungal biomass that can serve as EPA-fortified food or feed."
Athalye and colleagues published their study in the Journal of Agricultural and Food Chemistry ("Use of Biodiesel-Derived Crude Glycerol for Producing Eicosapentaenoic Acid (EPA) by the Fungus Pythium irregulare." Journal of Agricultural and Food Chemistry, 2009;57(7):2739-2744).
For additional information, contact Z.Y. Wen, Virginia Polytechnic Institute & State University, Dept. of Biology Systems Engineering, Blacksburg, VA 24061.
From the May 11, 2009, Prepared Foods E-dition