Reduction of nucleic acid content in yeast cells

Four methods to reduce nucleic acid content in Candida utilis TISTR 5001 and Saccharomyces cerevisiae TISTR 5017 were investigated as follows: 1) three-step heat treatment 2) heat treatment with ammonium hydroxide 3) heat treatment with sodium chloride and 4) heat treatment with ribonuclease A. With the three-step heat treatment, an optimal condition was obtained by heating first 70 deg C for 18 seconds, then at 45 deg C for 2 hours and finally at 55 deg C for 1 hour. It was found that percent reduction of nucleic acid and protein loss were 37.55 and 21.41 in C. utilis TISTR 5001 and 46.24 and 46.14 in S. cerevisiae TISTR 5017, respectively. The nucleic acid content left in C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were 4.36 and 4.05 percent dry weight, respectively. The reduction of nucleic acid in S. cerevisiae TISTR 5017 was better than in C. utilis TISTR 5001, but higher protein loss. Using heat treatment with ammonium hydroxide, optimal conditions for C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were obtained by treating the samples with 2 and 3 percent NH4OH at 70 deg C for 30 minutes, respectively. It turned out that percent reduction of nucleic acidand protein loss were 88.13 and 14.22 in C. utilis TISTR 5001 and 82.55 and 18.78 in S. cerevisiae TISTR 5017. The nucleic acid content left in C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were 1.17 and 1.56 percent dry weight, respectively. However, using this method the reduction of nucleic acid in C. utilis TISTR 5001 was better than in S. cerevisiae TISTR 5017 with lower protein loss. Using heat treatment with sodium chloride, an optimal condition for both strains was obtained by treating the samples with 0.4 M NaCl at 75 deg C for 30 minutes. The reduction of nucleic acid and protein loss were 56.88 and 21.80 percent in C. utilis TISTR 5001 and 54.41 and 22.86 percent in S. cerevisiae TISTR 5017, respectively. The nucleic acid content left in C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were 3.41 and 3.48 percent dry weight, respectively. The reduction of nucleic acid in C. utilis TISTR 5001 was better than in S. cerevisiae TISTR 5017 with lower protein loss. Using heat treatment with ribonuclease A, optimal conditions for C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were obtained by treating the samples with 200 micro g/ml ribonuclease A at 55 deg C for 30 minutes and 90 minutes, respectively. The reduction of nucleic acid and protein loss were 87.97 and 2.94 percent in C. utilis TISTR 5001 and 89.27 and 10.72 percent in S. cerevisiae TISTR 5017. The nucleic acid content left in C. utilis TISTR 5001 and S. cerevisiae TISTR 5017 were 0.61 and 0.58 percent dry weight, respectively. The reduction of nucleic acid in S. cerevisiae TISTR 5017 was better than in C. utilis TISTR 5001 but higher protein loss.