Hydrothermal decomposition of yeast cells for production of proteins and amino acids

摘要

This study examines hydrothermal decomposition of baker's yeast cells, used as a model for spent brewer's yeast waste, into protein and amino acids. Sub-critical water extraction is an alternative non-catalytic process to recover higher value protein and amino acid products from this waste. The reaction was carried out in a closed batch reactor at various temperatures between 100 and 250°C. The reaction products were separated into water-soluble and solid residue. It was found that the amount of yeast residue decreased with increasing hydrolysis temperature. After 20 min of hydrolysis reaction at 250°C, 78% of yeast was decomposed. The highest amount of protein produced was also obtained at this condition and was found to be 0.16 mg/mg dry yeast (figure 1). The highest amount of amino acids (0.063 mg/mg dry yeast) was found at the lowest temperature tested after 15 min. We employed the hydrolysis product obtained after 5 min at 200°C as a nutrient source for the culture of yeast cells. The result demonstrated that the yeast extract prepared by hydrolysis in sub-critical water could positively be applied for the cultivation of yeast cells and gave the growth that did not significantly differ from that obtained using a commercial yeast extract (figure 2). In addition, the decomposition kinetic model and the associated kinetic parameters were determined.