Food Technology

Dr. Dimitris Sarris has completed his PhD in Food Biotechnology and 3 post-doc research projects at Agricultural University of Athens, Greece. He is currently an Assistant Professor in Molecular Biology & Food Biotechnology in the Department of Food Science and Nutrition, School of the Environment, University of the Aegean, Greece. He has published 13 papers in reputed journals and has been serving as a reviewer in more than 10 journals. Amongst his scientific interests are the treatment and valorization of agro-industrial by-products and wastes (and in general food industry effluents) via biotechnological processes for the production of (high-) added value products.

Crude glycerol is the main by-product of alcoholic beverage and oleochemical production activities (including biodiesel production). The tremendous quantities of glycerol produced worldwide represent a serious environmental challenge. The aim of this study was to investigate the ability of Yarrowia lipolytica strain ACA-DC 5029 to grow on nitrogen-limited submerged shakeflask cultures, in media with ascending initial glycerol concentration (~70

g/L, ~120 g/L and ~170 g/L) and produce cellular mass, cellular lipids, citric acid and polyols. The yeast strain managed to fully assimilate crude glycerol in all experiments. In media with initial glycerol concentration (Glol0~70 g/L) maximum biomass production (Xmax) was 11.96 g/L (yield of biomass produced on substrate consumed, YX/Glol=0.17 g/g) and maximum production of cellular lipid (Lmax) 1.27 g/L (yield of microbial lipid produced on dry biomass produced YL/X=10.6% w/w). Maximum citric acid production (Citmax) was 42.5 g/L (yield of citric acid produced on substrate consumed, YCit/Glol=0.59 g/g) and maximum erythritol production (Erymax) was 14.9 g/L (yield of erythritol produced on substrate consumed, YEry/Glol=0.23 g/g). In media with Glol0~120, Xmax was 12.40 g/L (YX/Glol=0.10 g/g) and Lmax was 2.07 g/L (YL/X=19.7% w/w). Citmax was 63.8 g/L (YCit/Glol=0.52 g/g) and Erymax was 38.4 g/L (YEry/Glol=0.40 g/g). In media with Glol0~170 g/L, a shift towards erythritol production was noted (Erymax~66.0 g/L, YEry/Glol~0.39 g/g) simultaneously with high amounts of produced citric acid (Citmax~79.0 g/L, YCit/Glol~0.46 g/g). Xmax was 12.48 g/L (YX/ Glol=0.08 g/g) and Lmax was 2.54 g/L (YL/X=22.4% w/w) suggesting that higher concentrations of crude glycerol in the media clearly favoured the production of cellular lipid. Fatty acid analysis of microbial lipids demonstrated that in media with high glycerol concentration, oleic acid production was favoured.