Effect of gamma irradiation on the growth and fermentation activity of yeast to produce sugar

anglais. An experiment to study the effect of gamma irradiation on colony forming of yeast and dissolving sugar as the fermentation products, was carried out. At logarithmic phase, the yeast suspension was irradiated by gamma rays with 2 steps of experiments. Irradiation doses used in the first experiment were 0; 0.1; 0.2; 0.3; 0.4; and 0.5 kGy, whereas the doses of 0; 0.6; 0.7; 0.8; 0.9; and 1.0 kGy were used in the second experiment. The dose rate of irradiated yeast suspensions into medium containing 5 percent (w/v) tapioca starch, then shaked at 100 ppm with the temperature of 30 degrees C. At the fermentation time of 24, 48, 72, and 144 hours, glucose and reduction of sugar contents were analysed. Total plate count of irradiated and unirradiated yeasts were determined after 3 days. Results of the first experiment showed that the ability of yeast from the colonies increased at the doses of 0.1 kGy to 0.4 kGy (P0.05), whereas at the dose of 0.5 kGy the number of yeast colonies decreased. Glucose and reduction sugar contents significantly increased by using the irradiated yeast mentioned above (P0.01 and P0.05) and the highest enhancement resulted from the irradiated yeast of 0.4 kGy. The number of yeast colonies at the second experiment significantly decreased (P0.01), whereas the irradiation effect on glucose production was not significant but the reduction sugar significantly increased (P0.05). Longer fermentation time either at first or second experiments revealed increase in glucose and reduction sugar contents (P0.01)

indonésien. Telah dilakukan percobaan untuk mengetahui pengaruh iradiasi sinar gamma pada pertumbuhan koloni khamir dan gula terlarut hasil fermentasi. Suspensi khamir pada fase logaritma diiradiasi (kontrol) ke dalam medium yang mengandung 5 persen (b/v) tepung tapioka kemudian digoyang dengan 100 putaran per menit pada suhu 30 derajat C. Analisis kadar glukose dan gula pereduksi ditentukan pada waktu fermentasi 24, 48, 72, dan 144 jam. Penghitungan jumlah koloni khamir iradiasi dan kontrol dilakukan setelah 3 hari. Hasil percobaan I menunjukkan iradiasi gamma dengan dosis 0,1 s/d 0, 4 kGy pada khamir meningkatkan jumlah koloninya (P0,05), sedangkan pada dosis 0,5 kGy jumlah tersebut menurun. Pengaruh iradiasi juga meningkatkan hasil glukosa (P0,01) dan gula pereduksi (P0,05), peningkatan tertinggi dihasilkan oleh khamir yang diiradiasi pada dosis 0,4 kGy.