Protein production from cellulosic waste using candida utilis

Abstract

With rapid population growth there is a lot of interest in developing alternative protein sources, like protein yeast cultures. For growth of yeast could be used agricultural and food processing waste, but such source of hydrocarbons need to be pretreated. The purpose of the presented study is to assess the effect of steam explosion treatment on the process of feed protein production, including the influence on the enzymatic hydrolysis, cultivation of yeast and resulting products characteristics. Wheat straw, spelt hull and sunflower husk were subjected to steam explosive activation at 165 °C and 210 °C. The products were subjected to enzymatic hydrolysis at the following conditions: enzyme dose 12 g/kg of raw material and temperature of 45 °C. Total reducing sugars content and component composition were evaluated in the hydrolysates using IR spectrometry and HPLC respectively. A pure yeast culture of Candida utilis, was grown on hydrolysates (2 g/L) in a 10 L bioreactor unit at 35 °C for 24 h. The samples of protein were evaluated for crude protein, true protein, fiber, fat and ash content. Conversion efficiency was calculated. The highest conversion efficiency was observed for spelt husks activated at 165 °C: reducing sugars yield was 56.2 % out of 73.3 % of theoretical yield; biomass concentration reaches 52.9 g/L, with reducing sugar conversion of 80.1 %. The crude protein content of yeast was 53.9 % (42 % according to Barnstein). Hydrolysates from activated materials, give a higher yeast biomass yield of 21–42 % compared to hydrolysates of non-activated raw materials.