Nucleotides

Through hydrolysis of RNA, nucleotides such as inosinic acid and guanyl acid are formed and used for seasonings. Ribonucleotides are produced by the combination of extraction,

Table 10 Wastewater Load of Bread Yeast Production

Amount of use, a (kg/day)

Generated Loss Discharged load, b rate, b/a load, c (t/day) (kg/day)* (%)

Reduction rate, 1- c/b (%)

Unit loading factor (kg/t yeast)**

CODMn

-

6750 - 80

99

33

TN

626

50 8 14

72

16

TP

88

3 3 1

44

0.06

^Excluding other nontreated wastewater; "Assuming moisture of yeast is 68%.

^Excluding other nontreated wastewater; "Assuming moisture of yeast is 68%.

Figure 6 Estimated flow of wastewater in the production of MSG.
Table 11 Wastewater Load of MSG Production

Amount of

Generated Loss Discharged

Reduction

Unit loading

use, a

load, b (t/day) rate, b/a load, c (t/day)

rate, 1-c/b

factor (t/t

(t/day)

(%)

(%)

MSG)

CODMn

-

- - 0.50

-

0.015

TN

4.6

1.8 39.1 1.00

44.4

0.030

TP

0.09

0.09 100.0 0.05

43.2

0.002

fermentation, and chemical synthesis. During fermentation, yeast capable of accumulating RNA is cultured and forms ribonucleotides through enzymic hydrolysis of extracted RNA from the yeast. Finally, ribonucleotides are purified through ion exchange resins, crystallized, and dried to become the products. The main part of wastewater is derived from the yeast separation and purifying processes as shown in Fig. 7.

As these products consist of finer materials, the loss rate may be larger than in the case of MSG. Therefore, various byproducts are recovered. The spent cell of the yeast is utilized for feedstuff and the concentrated part of the wastewater from the purifying process is used as liquid fertilizer after further concentration. A fraction of the wastewater of medium concentration is treated by the activated sludge process. After separating the yeast cells, the wastewater is treated by an activated sludge process of deep shaft aeration. Molasses had been used previously in this process, but acetic acid replaced it as a countermeasure for reducing wastewater load. Table 12 shows the balance of N and P as the result of estimation shown in Table 13. The rate of loss is very large at

Figure 7 Estimated flow of N and P in the production of ribonucleotides.
Table 12 Wastewater Load of Ribonucleotides Production

Amount of

Generated

Loss

Discharged

Reduction

Unit loading

use, a

load, b

rate,

load, c (t/day)

rate, 1-c/b

factor (t/t of

(t/day)

(t/day)

b/a (%)

(%)

nucleotide)

CODMn -

11.01

-

0.67

94

0.24

TN 5.16

3.90

76

1.74

55

0.62

TP 1.24

0.74

62

0.49

33

0.17

76% for TN and 62% for TP. The unit loading factor of CODMn, TN, and TP after treatment was 240 kg/t, 620 kg/t, and 170 kg/t, respectively. The removal rate was 94% for CODMn, 56% for TN, and 33% for TP.

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