Successful fodder yeast production from agro-industrial by products through a statistical optimization approach
Abstract
The present work focused on the fodder yeast production, an attractive source of proteins for the livestock nutrition through the efficient growth of microorganisms on inexpensive waste substrates. Two agricultural by-products, sugar beet pulp and barley husks, rich in simple carbohydrates (88 g/L and 31.77 g/L for sugar beet hydrolysate and barley husks hydrolysate, respectively) were mixed after acid hydrolysis and used as a carbon and energy source for the "fodder yeast" Candida utilis production. Various nutritional requirements affecting the yeast growth were considered and investigated through an experimental design approach. The Response Surface Methodology was applied in order to optimize the medium composition aiming to increase on the one hand the yield on biomass rich in protein content and the substrate bioconversion on the other hand. Statistical analysis of the mathematical models developed for the studied response functions revealed a good correlation between the experimental data and the predicted values. In a medium containing 32-34 g/L reducing sugar, 1.022-1.079 g/L nitrogen and 0.406-0.427 g/L phosphorous, 6.47-6.62 g/L biomass were obtained. Under these conditions the final product protein content was of 50.40-51.55% (w/w) for a substrate consumption yield (expressed as monosaccharides content) of 92.94-95.4% (w/w).