Characterization of microbial biomass production from glycerin waste by various yeast strains
Piotr Juszczyk , Waldemar Rymowicz
AbstractThe conversion of glycerin waste from ethyl ester biodiesel production into a protein source for animal feed was examined. In the study, six yeast strains were used for biomass production: Yarrowia lipolytica ATCC 8661, Y. lipolytica ATCC 8661 UV'1, Y. lipolytica A-101, Y. lipolytica Z, Candida robusta ATCC 60 559, and C. utilis ATCC 60 558. The glycerin waste, a main by-product of biodiesel industry, contained (w/w) 45% of raw glycerol, 44% of fatty acids, 3-4% of ethyl esters, and large quantities of potassium soaps. Since the pH of the substrate was 9.6, glycerin waste was added batchwise during yeast growth, in order to prevent the pH value from exceeding 4.0. All experiments were conducted in a stirred tank reactor, on media containing 30 g/L of glycerin waste as a substrate. The results of the experiments have shown that the strain Y. lipolytica 8661 UV'1 is the most suitable for biomass production from this substrate. During batch cultivation, the strain simultaneously utilized glycerol and fatty acids. The biomass yield and biomass production rate obtained with this strain were the highest at 0.89 g/g and 2.7 g/Lh, respectively. Protein concentration in the biomass varied from 26.5 to 36.5% (w/w), depending on the yeast strain used. The content of essential amino acids was in compliance with the FAO/WHO standards for fodder yeast, valine and isoleucine occurring in the yeast biomass in higher quantities. The nutritional value of the yeast obtained in a submerged culture on glycerin waste ranged between 64 and 70% according to Oser's Essential Amino Acid Index (EAAI). Analysis of technological parameters (biomass yields, volumetric biomass production rate and protein content has also revealed that the strain Y. lipolytica ATCC 8661 UV'1 is the most efficient biomass producer from glycerin waste. The results are very promising, as these findings may lead to a low-cost process of fodder yeast biosynthesis from a waste generated during biodiesel production.
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|Book||Aggelis George (eds.): Microbial Conversions of Raw Glycerol, 2009, Nova Science Publishers, ISBN 978-1606923924, 197 p.|
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